BIOLOGY AND MANAGEMENT OF BLUEBERRY GALL MIDGE AND SCALE
INSECTS IN MICHIGAN BLUEBERRIES
By
Noel Hahn

A THESIS
Submitted to
Michigan State University
in partial fulfillment of the requirements
for the degree of
MASTER OF SCIENCE
Entomology
2011

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ABSTRACT
BIOLOGY AND MANAGEMENT OF BLUEBERRY GALL MIDGE AND SCALE
INSECTS IN MICHIGAN BLUEBERRIES
By
Noel G. Hahn
Blueberry gall midge (Dasineura oxycoccana), European fruit lecanium scale
(Parthenolecanium cornii) and Putnam scale (Diaspidiotus ancylus) are potential pests of
Vaccinium crops, including blueberry and cranberry. The blueberry gall midge has recently
increased in abundance in Michigan blueberries, causing high levels of damage to young green
shoot tips. Scale insects have been found in localized areas with erratic population levels. The
distribution of these pests in Michigan blueberries, their phenology and the effects of their
damage on blueberry plants are unknown, limiting development of management programs.
During 2009, surveys were conducted in blueberry farms and nurseries in Michigan to determine
the distribution of D. oxycoccana in the state. To determine the phenology of blueberry gall
midge, during 2009 and 2010, adult midges in blueberry fields were sampled using emergence
traps, yellow sticky traps, and shoot tip dissections. Multiple peaks of damage and larval
infestation were found in June and July during shoot growth. Due to the lack of scale-infested
fields, monitoring of scale insects was limited to select farms known to be infested with the pest.
Insecticide trials on both the blueberry gall midge and Putnam scale were conducted at farm sites
and as bioassays in the laboratory. To determine the level of economic impact of blueberry gall
midge, in the falls of 2009 and 2010, fruit bud abundance was compared between branched
infested shoots and single uninfested shoots. Individual branches of infested shoots were found
to have fewer flower buds than uninfested shoots, but overall bud numbers per shoot were
similar.
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ACKNOWLEDGEMENTS

I thank Rufus Isaacs, Eric Hanson, and Deb McCullough from their guidance as I worked
towards my M.S. at Michigan State University. For their hard work on this project, I thank John
Pote, Jessica Chung, Jeff Hawk, Laurel Lindeman, Aaron Petrovich, and Katie O‟Donnell for
their assistance with field and lab work. This work could not have been accomplished without
the help of the Small Fruit Entomology Lab group. I would like to thank Keith Mason, Luis
Teixeira, Julianna Tuell, Steve Van Timmeren, Brett Blaauw, and Annie Kirk for their assistance
with experiments and for allowing me to bounce ideas off of them. John Wise, Ryan Vander
Poppen, Laura Lamb, Carlos Garcia and Ana Maria Gomez and Daisy at the Trevor Nichols
Research Center have been incredibly accommodating to me at the research station and
dormitory. Thanks to David Francis at the Southwest Michigan Research and Extension Center
for his excellent management of the farm. I also thank Blair Sampson for identification of
blueberry gall midge parasitoids. I‟m grateful for the advice and support the faculty and staff in
the Department of Entomology have provided for me, especially from Chris DiFonzo, John
Wise, Matt Grieshop, Ernest Delfosse and Heather Lenartson-Kluge. My friend George Boettner,
my parents Hyo-kun and Soonkyung Hahn, and my wife Jessica Chung have been essential parts
of my life throughout the past two years, encouraging and supporting me with their
conversations. I acknowledge Project GREEEN, the Professional Hutson award, and the John
Woodruff Simpson Amherst fellowship for funding this research.

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TABLE OF CONTENTS

LIST OF TABLES .......................................................................................................................vi
LIST OF FIGURES ....................................................................................................................vii
CHAPTER 1: BLUEBERRY GALL MIDGE AND SCALE INSECTS: EMERGING
PESTS OF MICHIGAN BLUEBERRY FARMS
The blueberry industry in Michigan ...................................................................................1
Insect pests in blueberries....................................................................................................2
Integrated pest management in blueberry ...........................................................................3
Blueberry pests and the Guthion phaseout ..........................................................................4
Secondary pests ...................................................................................................................6
Blueberry gall midge ...........................................................................................................7
Monitoring and management of blueberry gall midge .......................................................8
Scale insects in blueberries ...............................................................................................10
Scale biology .....................................................................................................................11
Management of scale insects ............................................................................................12
Scale insects in Michigan ..................................................................................................13
Justification for research ...................................................................................................15
CHAPTER 2: DISTRIBUTION AND PHENOLOGY OF BLUEBERRY GALL MIDGE,
(DASINEURA OXYCOCCANA) IN MICHIGAN
Abstract .............................................................................................................................17
Introduction .......................................................................................................................18
Distribution ...........................................................................................................18
Biology ..................................................................................................................19
Damage and symptoms .........................................................................................19
Methods .............................................................................................................................21
Selecting surveying sites .......................................................................................21
Surveying methods ................................................................................................22
Phenology of blueberry gall midge infestation .....................................................23
Degree day-based phenology ................................................................................26
Statistical analysis .................................................................................................26
Results ...............................................................................................................................27
Surveys for blueberry gall midge ..........................................................................27
Observational sampling for blueberry gall midge phenology ...............................30
Yellow sticky traps ...............................................................................................34
Emergence traps ....................................................................................................35
Shoot tip dissections .............................................................................................36
Growing degree days ............................................................................................37
Discussion .........................................................................................................................39

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CHAPTER 3: BIOLOGICAL AND CHEMICAL CONTROL OF BLUEBERRY GALL
MIDGE (DASINEURA OXYCOCCANA) IN MICHIGAN BLUEBERRIES
Abstract .............................................................................................................................43
Introduction .......................................................................................................................44
Methods .............................................................................................................................46
Bioassay ................................................................................................................46
Field insecticide trial .............................................................................................47
Survey for natural enemies and parasitoids ..........................................................48
Statistical analysis .................................................................................................50
Results ...............................................................................................................................50
Bioassay ................................................................................................................50
Discussion .........................................................................................................................53
CHAPTER 4: ECONOMIC IMPORTANCE OF BLUEBERRY GALL MIDGE IN
HIGHBUSH BLUEBERRIES
Abstract .............................................................................................................................56
Introduction .......................................................................................................................57
Blueberry shoot development ...............................................................................58
Blueberry gall midge damage and symptoms ............................... .......................59
Materials and Methods ......................................................................................................60
Effects of blueberry gall midge on highbush blueberry ........................................60
Statistical analysis .................................................................................................62
Results ...............................................................................................................................62
Discussion .........................................................................................................................65
CHAPTER 5: PHENOLOGY AND CHEMICAL CONTROL OF SCALE INSECTS IN
HIGHBUSH BLUEBERRY
Abstract .............................................................................................................................68
Introduction .......................................................................................................................68
Methods .............................................................................................................................71
Monitoring of Putnam scale and lecanium scale crawlers ....................................71
Fruit sampling for Putnam scale ...........................................................................73
Insecticidal control of lecanium scale ...................................................................73
Results ...............................................................................................................................75
Monitoring of Putnam scale and lecanium scale crawlers ....................................75
Fruit sampling for Putnam scale ...........................................................................77
Insecticidal control of lecanium scale ...................................................................77
Discussion .........................................................................................................................79
CHAPTER 6: CONCLUSIONS AND FUTURE RESEARCH...............................................82
APPENDIX...................................................................................................................................85
REFERENCES CITED...............................................................................................................87

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LIST OF TABLES

Table 1.1. World production of blueberries and percent of production, Selected countries.
(FAO, 2009) ....................................................................................................................................1
Table 1.2. Highbush blueberry rankings by state, Utilized Production (FAO, 2005) ...................2
Table 2.1. Number of farms and nurseries surveyed for blueberry gall midge in counties in
Michigan .......................................................................................................................................21
Table 2.2. Cultivars of highbush blueberry that were surveyed for blueberry gall midge ...........22
Table 2.3. Average percent infestation of shoots (±S.E.) by blueberry gall midge infestation in
Michigan blueberry farms, by county ...........................................................................................28
Table 2.4. Average percent infestation (±S.E.) by blueberry gall midge at Michigan blueberry
nurseries, by cultivar .....................................................................................................................28
Table 2.5. Average number of adult blueberry gall midge (± S.E) caught in emergence traps at
the east, west, north and south aspects at four fields on six randomly selected bushes during each
month in 2010 ...............................................................................................................................36
Table 3.1. List of insecticides used for the bioassay of blueberry gall midge .............................46
Table 3.2. List of insecticides used for the field insecticide trial of blueberry gall midge ..........48
Table 3.3. Average number of blueberry gall midge adults emerging (± S.E.) after treatment with
different insecticides. Values followed by the same letters were not significantly different .......51
Table 3.4. Average (± S.E.) proportion of susceptible shoots infested with blueberry gall midge
per bush as a function of insecticide treatments applied during the spring of 2010. There was no
significant difference between the treatments and the controls on any sampling date .................52
Table 4.1. The number of flower buds (± S.E.) in fall of 2009 and 2010 and spring of 2010 and
2011 on uninfested shoots and shoots infested by blueberry gall midge ......................................63
Table 4.2. The number of flower buds (± S.E.) in fall of 2009 and 2010 and spring of 2010 and
2011 on uninfested shoots and branches of shoots infested by blueberry gall midge ..................64
Table 5.1. Treatments used in the insecticide bioassay of European fruit lecanium scale ..........74
Table 5.2. Control of European fruit lecanium scale in laboratory bioassay. Mortality values
followed by the same letter are not significantly different ...........................................................78

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Table 5.3. Field insecticide trial for control of European fruit lecanium scale. Values are % scale
mortality per shoot. There was no control treatment ....................................................................78
Table A.1. Voucher Specimen Data ......................................................................................86

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LIST OF FIGURES

Figure 2.1. Emergence trap used to capture adult midges. The trap is comprised of a bucket with
the bottom removed, covered with a large Petri dish that has tanglefoot glue smeared on the inner
surface. For interpretation of the references to color in this and all other figures, the reader is
referred to the electronic version of this thesis .............................................................................25
Figure 2.2. Average (± S.E.) percent infestation of Michigan blueberry farms by blueberry gall
midge. Bars following county name differentiate individual surveyed farms within a county ....29
Figure 2.3. Percent infestation of blueberry gall midge (± S.E.) in Michigan blueberry nursery
plots. Numbers 1-4 indicate different nurseries. Letters A, B, and C indicate different surveyed
plots within nurseries ....................................................................................................................30
Figure 2.4. Variation in percent infestation (± S.E.) of new shoots by blueberry gall midge at
Michigan farms during 2009. The number of growing new shoots was counted at the beginning
of the growing season ...................................................................................................................31
Figure 2.5. Variation in percent infestation (± S.E.) of elongating shoot tips by blueberry gall
midge at Michigan farms during 2010. The number of vulnerable shoot tips was counted each
week ..............................................................................................................................................31
Figure 2.6. Variation in the percent infestation (± S.E.) on the top, middle and bottom third of
blueberry bushes at Michigan farms during 2010 .........................................................................32
Figure 2.7. Variation in the number of vulnerable shoot tips (± S.E.) on blueberry bushes at
Michigan farms during 2010 .........................................................................................................33
Figure 2.8. Variation in the number of vulnerable shoot tips (± S.E.) in the top, middle, and
bottom third of blueberry bushes at Michigan farms during 2010 ...............................................33
Figure 2.9. The total number of blueberry gall midge caught on yellow sticky traps placed in
infested blueberry fields in 2010 ...................................................................................................34
Figure 2.10. The total number of adult blueberry gall midge caught in emergence traps during
2010 ...............................................................................................................................................35
Figure 2.11. Variation in the number of blueberry gall midge larvae (± S.E.) from dissections of
shoots collected at infested blueberry fields in 2010 ....................................................................37
Figure 2.12. The number of blueberry gall midge larvae found in shoot tips of blueberry shoots,
separated by instar .........................................................................................................................38

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Figure 2.13. Average (± S.E.) number of blueberry gall midge larvae found in shoot tips of
differing colors .............................................................................................................................38
Figure 2.14. Estimate of the number of blueberry gall midge larvae per bush (± S.E.) in 2010 .39
Figure 4.1. Buds on a highbush blueberry shoot that is uninfested (A) and infested (B) by
blueberry gall midge .....................................................................................................................61
Figure 4.2. Mean (± S.E) number of flower buds (± S.E) in fall of 2010 and 2011 on uninfested
blueberry shoots and shoots infested by blueberry gall midge compared by month of damage.
Bars with the same letter are not significantly different (P < 0.05) ..............................................65
Figure 5.1. Phenology (crawlers per tape ± S.E.) of Putnam scale and European fruit lecanium
scale crawlers on Michigan blueberry in 2009. Species could not be separated at the crawler
stage ..............................................................................................................................................76
Figure 5.2. Phenology (crawlers per tape ± S.E.) of European fruit lecanium scale crawlers on
Michigan blueberry in 2010 .........................................................................................................76
Figure 5.3. Phenology (crawlers per tape ± S.E.) of European fruit lecanium scale on blueberry
leaves in 2010 ...............................................................................................................................77

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CHAPTER 1

BLUEBERRY GALL MIDGE AND SCALE INSECTS: EMERGING PESTS OF
MICHIGAN BLUEBERRY FARMS

THE BLUEBERRY INDUSTRY IN MICHIGAN
Blueberries are plants of the genus Vaccinium that have become an important specialty crop to
consumers. There has been increasing production globally and in the United States. According to
the Food and Agriculture Organization of the United Nations statistical database, globally since
1990, blueberry yield has increased from 124,324 metric tons to 288,600 tons per year. The
United States is the leading blueberry producer in the world (Table 1.1), growing 51% of the
world‟s supply. Since 1990 in the United States, blueberry production has increased twofold
from 79,940 to 158,032 metric tons. Michigan is the leading producer and exporter of highbush
blueberries (Vaccinium corymbosum L.) in the United States (Table 1.2), and contains a third of
the country‟s acreage of this crop.
Table 1.1. World production of blueberries and percent of production, Selected
countries. (FAO, 2009).
Country
United States
Canada
Poland
Germany
Netherlands
Ukraine
Lithuania
Other countries
World

Production (metric tons)
158,032
95,516
7,857
4,116
4,000
3,000
2,500
13579
288,600

1

Percent
55
33
3
1
1
1
1
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Table 1.2. Highbush blueberry rankings by state, Utilized Production (FAO,
2005)
State
Michigan
New Jersey
Oregon
Georgia
North Carolina
Washington
California
Florida
Mississippi
Indiana
Total

Rank
1
2
3
4
5
6
7
8
9
10

Production (1,000 lbs)
83,000
52,000
35,600
31,500
25,500
19,000
10,000
7,000
4,600
3,400
271,600

INSECT PESTS IN BLUEBERRIES
The blueberry industry in Michigan has historically needed to respond to invasive and
native pest species to maintain high yields and fruit quality. These pests include direct pests,
those that attack the fruit, and indirect pests, those that feed on foliage, sap and growing buds
that may have an effect on yield. Invasive pests are non-native species that are introduced into an
ecosystem and cause economic or environmental damage. For example, the spotted wing
Drosophila (Drosophila suzukii Matsumura), an invasive vinegar fly that directly infests
blueberries with the potential to cause massive loss of marketable fruit, was first found in late
2010 in Michigan. In Washington and Oregon, it has already caused considerable damage to the
blueberry industry (Steck et al. 2009). An example of a native pest that indirectly affects
blueberry plants is the blueberry aphid (Illinoia pepperi McGillivary), an insect of the family
Hemiptera that feeds on the sap of blueberry plants and is a vector of blueberry shoestring virus.
Blueberry maggot (Rhagoletis mendax Curran), cranberry fruitworm (Acrobasis vaccinii Riley)
and obliquebanded leafroller (Choristoneura rosaceana Harris) are three other common native
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blueberry insect pests that require active management. There are also secondary pests, which are
insects that under normal conditions would not be causing damage over the economic threshold.
Circumstances such as loss of its natural enemies from habitat loss or insecticide use or the
opening of a favorable niche could provide the insect with the opportunity to become a pest.

INTEGRATED PEST MANAGEMENT IN BLUEBERRIES
Integrated pest management (IPM) is an approach to pest management that was developed after
synthetic pesticides were introduced in the 1940s (Stern et al. 1959, Kogan 1998). IPM includes
a variety of practices that incorporate economic thresholds, monitoring, prevention, and control
using biological and chemical approaches. The first step in an IPM program is the establishment
of economic thresholds, to determine the point at which the insect pest is causing substantial
economic damage to the crop, and action thresholds, the point at which an insect pest‟s
population is high enough to warrant management (Pedigo 2006). The second step is to monitor
for the pest using traps or scouting to determine if populations have reached the action threshold.
The third is to prevent pests from becoming economically threatening. Prevention measures
include cultural controls such as the selection of resistant cultivars and rotation of crops. If the
pest manages to become established at threshold levels, management techniques are needed to
control it. Management of a pest includes use of mechanical control such as tilling and pruning,
biological control such as introduction of natural enemies, and chemical control with
insecticides. IPM has been successful in many systems, such as with the management of
Southwestern corn borer, Diatraea grandiosella (Dyer), in North Carolina (Chippendale and
Sorenson 2006) and control of soybean insect pests in Ohio (Hammond 2006).

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In blueberries, key pests that are currently being managed are blueberry maggot, cherry
(Grapholita packardi Zeller) and cranberry fruitworms, aphids and Japanese beetle (Popillia
japonica Newman). Phenological and growing degree day models for these and other insects
have been developed, and the most effective insecticidal, cultural and mechanical treatments
have been determined. For example, a growing degree day model has been developed for the
whitemarked tussock moth, Orgyia leucostigma (J. E. Smith), a pest that defoliates blueberry
bushes (Isaacs and Van Timmeren 2009). This information should help growers determine the
optimal timing to apply insecticides that will target eggs and young larvae while avoiding risk to
pollinators and natural enemies.

BLUEBERRY PESTS AND THE GUTHION PHASEOUT
Blueberry pests are typically controlled through the use of broad or narrow-spectrum insecticides
that can target a wide range or a narrow range of species, respectively. Common broad-spectrum
insecticides tend to be less expensive than narrow-spectrum insecticides, and they do not require
multiple sprays to target different insects. However, in addition to killing pest insects, broadspectrum pesticides are likely to also kill beneficial insects (Hull and Starner 1983, Gentz et al.
2010). The Food Quality Protection Act of 1986 (FQPA) amended the Federal Insecticide,
Fungicide, and Rodenticide Act (FIFRA) and the Federal Food, Drug, and Cosmetic Act
(FFDCA). The FIFRA set guidelines for the use of pesticides, their registration and their
classification. The FFDCA regulates the establishment of tolerances for pesticide use in food
crops. Under the FQPA amendments, numerous changes were made including new standards for
pesticide residues on food, streamlining of reduced-risk pesticide registration, and pesticide
reassessment by the US Environmental Protection Agency (EPA) every 15 years to see if they

4

meet current standards. These led to changes in pesticide labeling and use to reduce the
magnitude and toxicity of pesticide as well as exposure of workers and environment to residues,
and the decreased use of broad-spectrum pesticides in favor of narrow-spectrum insecticides
(DiFonzo 2006).
In 2006, US-EPA made the decision to phase out the remaining uses of the
organophosphate azinphosmethyl from fruit and nut crops by September 30, 2012. This
insecticide has been a crucial part of Michigan blueberry pest management to control cranberry
fruitworm, Acrobasis vaccinii, and cherry fruitworm, Grapholitha packardii, in mid-summer. In
Michigan blueberries in 2007, azinphosmethyl was the most-sprayed insecticide in June when
fruitworm is active, with 9,420 acres treated, and was the second most used insecticide in the
entire season, having been sprayed on 50.8% of blueberry acreage (Isaacs et al. 2008).
This phaseout is in line with one of EPA‟s goals, to promote the use of safer insecticides.
Azinphosmethyl has a relatively high risk to farm workers, pesticide applicators, and aquatic
ecosystems. During the phaseout, several changes have been made to the use of azinphosmethyl
in blueberries, such as a decrease in the number of applications that can be made per season,
elimination of aerial applications, and increased sizes of buffer zones around aquatic areas and
houses. This is forcing growers to quickly adopt new strategies to control for fruitworm pests.
Under the auspices of the Michigan Blueberry Azinphosmethyl Transition Strategy, the
blueberry industry is being educated on the use of other IPM practices and insecticides that can
control pests. Alternative insecticides such as neonicotinoids, spinosyns, and insect growth
regulators are being evaluated and some of these have shown performance similar to the level
provided by azinphosmethyl.

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Data from the USDA-NASS show a decrease in the use of broad-spectrum
organophosphates and carbamate insecticides as well as the increased use of reduced-risk
pesticides, such as methoxyfenozide and imidacloprid, and pyrethroids. Due to the reduction in
the use of broad-spectrum insecticides and the inability of narrow-spectrum insecticides to target
all insects, it is predicted that secondary pests will have the opportunity to increase their
populations. However, it is also possible that secondary pest populations could be stabilized by
natural enemies with the reduced insecticide pressure on those natural enemies. Pyrethroids and
reduced-risk pesticides have been shown to have a variety of different effects on natural enemies
of pests. In Pennsylvania apple orchards, pyrethroids were very toxic to predatory mites, but less
toxic to other natural enemies (Hull and Starner 1983). Grape berry moth has been found to
experience comparable or better control with the use of reduced-risk insecticides, but the natural
enemies experienced no change in population (Jenkins and Isaacs 2007).

SECONDARY PESTS
Secondary pests are those that under normal conditions would not be a significant problem for
growers; however, circumstances can give the insect the opportunity to invade and proliferate.
One example of a secondary pest is the invasion of rats resulting when the World Health
Organization sprayed large quantities of DDT in Borneo to control for mosquitoes. The gecko
population that fed on flies was weakened by the consumption of DDT-filled flies. In turn, the
cats that consumed the geckos died, allowing a rat infestation to take hold of many villages
(Time 1969). Another example of secondary pests is occurring in India with the overuse of
transgenic Bt cotton, which has protected their cotton crop from the American bollworm
(Helicoverpa armigera Hubner), and the consequential reduction in the number of sprays used.

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However, this has led to mealybug infestations on cotton, possibly due to introduction through Bt
corn seeds (Ho 2010)
Research focusing on understanding the biology and ecology of secondary pests has often
been a low priority because of their generally low economic impact. However, when they
experience a rapid population increase and become an economic threat, the need to understand
these topics aid development of management programs targeting these pests. The primary insect
pests of Michigan blueberries can be controlled with prudent IPM practices. There are other
pests of blueberries that do not pose as large an economic threat as the primary pests. However,
these secondary pests may be primary pests in other locations in the US or world.

BLUEBERRY GALL MIDGE
Blueberry gall midge (Dasineura oxycoccana Johnson) is one such secondary pest, and is a
potential pest of Vaccinium crops, including blueberry and cranberry. In the past few years, this
cecidomyiid species has been found more frequently in Michigan blueberry farms, where it can
cause high levels of damage to young vegetative shoot tips. It lays its eggs inside growing
vegetative shoot tips, and the larvae hatch and feed on the developing plant tissue. Feeding by
larvae induces a branching reaction in damaged shoots due to loss of apical dominance.
Blueberry gall midge has three instars, the first of which is only detectable with a high-powered
dissecting microscope. The third instar is about 2 mm long, and is an orange-pink color. The
length of time the midge takes from egg to adult is not known, but observations in the lab
indicate anywhere from two to four weeks. The distribution of D. oxycoccana in Michigan
blueberries, its phenology and the effects of its damage on fruit yield and bud set are unknown,
limiting development of a management program for this insect of increasing abundance.

7

Blueberry gall midge was found to be a pest in New Jersey cranberries by Marucci
(1977), but was said to be under control through the use of broad-spectrum insecticides such as
Guthion and Parathion. It was later found to be a problem in rabbiteye blueberries, Vaccinium
ashei Reade, in Florida, where it destroyed as much as 80% of the floral buds in commercial
plantings (Lyrene and Payne 1992). This floral bud damage was not observed in Michigan and so
there has been relatively little research conducted on blueberry gall midge in Great Lakes
blueberries. There has been some research by in Wisconsin cranberries, where the same insect is
called the cranberry tipworm and it causes shoot damage especially in more northern farms
where the new shoots that are produced after damage may not have time to harden before frost
(Mahr and Perry 2005). However, vegetative bud damage has recently become noticeable
throughout the year in Michigan blueberry fields, yet many questions remain about this insect‟s
biology and management in this system.

MONITORING AND MANAGEMENT OF BLUEBERRY GALL MIDGE
Understanding a pest‟s phenology and distribution are the first key steps to developing an
effective IPM program. These can be determined by sampling and trapping the pest. The
presence and level of biocontrol agents can also be surveyed while sampling. This gives an
indication of their ability to control the pest population in a farm setting. When the distribution
and peak infestation periods of the insect are known, sampling schemes can be used to target the
pest at specific times and locations to eliminate populations before they expand.
Following IPM practices, the economic threshold of blueberry gall midge should be
determined before making recommendations to growers. Although the midge has a significant
impact on rabbiteye blueberries in Florida (Lyrene and Payne 1992), evidence of damage to

8

floral buds has not been seen in Michigan highbush blueberries. However, the damaged shoots
experience lateral branching that could potentially cause a reduction in floral buds. There may
also be an increase in the susceptibility of young lateral shoots to winter kill. There have thus far
been no studies investigating the floral bud yield of shoots that have been damaged by blueberry
gall midge.
Monitoring techniques have been developed in other regions to track the populations of
this pest. Yellow sticky traps placed within fields have been used to detect adult midges and their
natural enemies and were found to catch significantly fewer adult midges than allowing for adult
emergence from collected buds. Fruit bud dissection to count larvae were found to be equally
effective at detecting the insect (Sarzynski and Liburd 2003). Emergence traps have also been
designed and tested to determine their effectiveness in trapping blueberry gall midge early and
throughout the season (Roubos and Liburd 2010). They were found to be useful in detecting
adults before any larval damage was apparent in fruit and vegetative buds.
Prior to widespread use in the field, pesticides should be tested on the pests in field and
laboratory settings to determine their efficacy. Thus far, only a handful of pesticide trials have
been conducted on blueberry gall midge. One study in Washington State blueberries tested
whether Bacillus thuringiensis (Gnatrol™), cyantraniliprole (Cyazypyr™), spinetoram
(Delegate™), spirotetramat (Movento™) or vegetable oil surfactant (Dyne-Amic™)
applications would reduce larval populations in infested shoot tips. Cyantraniliprole and
spirotetramat reduced larval levels 13 days after treatment (Tanigoshi et al. 2010). Another study
in rabbiteye blueberries indicated control by malathion, phosmet or spinosad, where malathion
was extremely effective and killed 94% of larval midges and phosmet and spinosad killed 50%

9

of larval midges (Sampson et al. 2002). These studies have utilized canopy sprays; there have not
been any trials investigating soil applications of systemic insecticides.
Biocontrol is another important part of an IPM program. Natural enemies and parasitoids
of blueberry gall midge were catalogued from Florida and Mississippi (Sampson et al. 2006).
Parasitoid eulophid wasps of the genus Apostocetus and Quadrastichus (Hymenoptera,
Platygastridae) were found to be present in gall midge populations. During peak blueberry gall
midge activity, 34% of larvae were found to be parasitized. Over the entire season, 7% of gall
midge larvae were found to be parasitized. The syrphid fly Toxomerus geminatus was also found
to be a predator of blueberry gall midge larvae.

SCALE INSECT PESTS
Scale insects, of which there are over 7,300 species, are phloem-sucking insects of the order
Hemiptera that are sporadic pests of fruit crops throughout the world (Miller and Davidson
2005). One-third of these, about 2,400 species, are armored scales (Family Diaspididae), and
about 1,000 species are soft scale insects (Family Coccidae). Others include mealybugs (Family
Pseudococcidae) and cottony cushion scales (Family Margarodidae). Armored scale insects have
been extensively reviewed by Miller and Davidson (2005) and by Rosen (2005). Ben-Dov and
Hodgson (2005) reviewed soft scale insects.
Scales are pests of perennial plants, and can cause substantial losses to fruit and nut trees,
forest trees, ornamentals, greenhouses, and other cultivated plantings. Miller and Davidson
(1990) list 199 armored scale pest species in the world, many of which are citrus pests.
Economic loss due to all scale insects has been estimated to be 5 billion US dollars annually

10

(Kosztarab and Kozár 1988). Due to the economic importance of scale insects, knowledge of
their biology and proper management is crucial.
Armored scales and soft scales are two economically important types of scale insects.
McClure (1990) describes the ecology of armored scales, which differs widely among species
and also within species. The ability of a scale insect to perform well in an environment depends
on many factors including climate, the attributes of the host, soil conditions, competition and
natural enemies. Suitability of host plants and habitat for scales can vary so much that introduced
species can often invade and infest hosts and habitats that are different from those of its native
range. The San Jose scale Quadraspidiotus perniciosus (Comstock), a pest of many tree fruits
including apple, peach and pear, has been found from China to Afghanistan to the United States
(Scalenet, http://www.sel.barc.usda.gov/scalenet/scalenet.htm). Stressed growing environments
and the lack of natural enemies can facilitate the establishment of invading scale insects. Studies
by McClure in 1990 showed that two ordinarily rare armored scales, F. externa and Nuculaspis
tsugae (Marlatt), could reach pest populations in cultivated fields of two plants, Tsuga
diversifolia Masters and Tsuga sieboldii Carrieré, that are ordinarily highly resistant to invasion
of scale in natural conditions. It was found that the scale insects were able to take advantage of
the stressed plants in poor growing habitat.

SCALE BIOLOGY
The rates of scale development and numbers of generations per year vary depending on the
temperature and climate of the region. For example, the olive scale, Parlatoria oleae, has two
generations in the Judean Hills of Israel, but at least three in the Beit-She‟an Valley. Those found
in the Judean Hills experienced a longer overwintering period than those in the Beit-She‟an

11

Valley (Applebaum and Rosen 1964). These authors concluded that temperature was the driving
factor in differing voltinism. This was tested in the lab on white peach scale, Pseudaulacaspis
pentagona, and the time required for one generation in the laboratory at 11-15˚ C was almost
three times longer than the time needed at 26˚ C (Ball 1980). In Maryland, this scale has three
generations per year; in Florida it has up to five per year.
Immature scale insects are called crawlers. While the female adult stage is sessile and
immobile, the crawlers are able to move to new feeding sites. Crawlers hatch from underneath
the scale covering of their parent and wander around until they settle (Greathead 1990).
Although most crawlers settle close to the parent, some wander to different parts of the plant and
others can be dispersed by the wind. Moving crawlers can be caught by using double-sided tape
wrapped around shoots. Elongate hemlock scale crawlers, Fiorinia externa, can be trapped on
sticky plates located in the canopy of a forest of Eastern hemlock (McClure 1979).

MANAGEMENT OF SCALE INSECTS
Damage by scale insects can destroy plant tissue, reduce plant growth and vigor, and lead to twig
dieback and premature leaf drop, increasing the plant‟s susceptibility to frost and disease.
Damage by soft scales can lead to contamination with honeydew, which is an ideal growing
medium for sooty mold. Sooty mold can spread over a leaf surface and cover it with black spots,
which impede photosynthesis and reduce growth.
In order to develop an integrated pest management (IPM) program for scale insects, a
comprehensive approach including biological, mechanical, chemical and cultural control must be
developed and implemented. Detection of scale insects through inspection of plants underneath
bark, around wounded areas, trunk and leaves is an important first step in the control of scale

12

insects. Because the biology and voltinism of scale insects differs so much between and even
within species, it is important to correctly identify potential scale pests and continue monitoring
for crawler emergence for use in a management program
Once scale insects have been detected and identified, the crawler stage and natural
enemies should be monitored to find peak emergence and to see if scale populations are
sufficiently suppressed by natural enemy populations. Control methods include chemical control
with horticultural oils and soaps, cultural control with pruning and use of resistant cultivars, and
biological control, either by introducing the scale‟s natural enemies or by timing insecticidal
sprays to not coincide with peak natural enemy populations.
Use of natural enemies to control populations is an important component of IPM that can
reduce the amount of pesticide use while reducing pest populations below the economic
threshold. Since scale insects are sessile, they are ideal targets for biological control, which
include pathogens, predators and parasites. Fungi account for some of the mortality in scale
populations, but have not yet been successfully used for scale control. Predators include
ladybeetles and mites. Parasites include hymenoptera of the families Aphelinidae, Encrytidae,
Signiphoridae and Aphelinidae.

SCALE INSECTS IN MICHIGAN
Recently, Lecanium scale (Parthenolecanium corni Bouché) and Putnam scale (Diaspidiotus
ancylus Putnam) have been found in blueberry plantings in localized regions of southwest
Michigan, and these insects may be experiencing high populations in these areas due to the
changing pesticide use. Lecanium scale has over 350 host species and is found throughout most
of the northern hemisphere. It has been a pest of a variety of food plants, from peaches in

13

Pennsylvania (Asquith 1949) and prunes in California (Bailey 1964) to ornamental plants in
Tbilisi (Japoshvili 2008). While this scale insect does not attack the fruit directly, accumulated
populations can cause plant death and high populations and the associated honeydew can cause
sooty mold on fruit, thereby reducing fruit quality. Putnam scale also has a number of hosts,
having been reported on 17 plant families and 30 genera (Borchsenius 1966). On blueberries,
heavy infestations can kill twigs and branches, and reduce plant vigor (Antonelli et al. 1992).
It is important to understand the scale insects‟ life cycle throughout the year so that the
vulnerable life stages can be targeted with cultural and insecticidal controls. Reports on the life
cycle of Putnam scale vary. Putnam scale was found to have one generation (Polvarapu 2000) or
two (Bray 1974). The life history of Lecanium scale and Putnam scale in Michigan blueberries is
unknown. Further information is needed to develop a management program for these scale
insects in Michigan.
Some scale insects first emerge in the spring from underneath their dead mother‟s
protective covering. Others overwinter as nymphs and enter a period of dormancy. In the spring,
scale insects in their nymph crawler stage will feed until later instars, when they settle on shoots
and form their waxy cover, becoming sessile (Miller 1997). The number of generations is
variable depending on the species. Putnam scale in New Jersey emerged as second instar nymphs
in the spring and proceed through two generations before overwintering again as nymphs.
Lecanium scale overwinters as second instar nymphs that mature in April and May, and have one
to two generations per year.
Scale insects are typically monitored for by careful visual inspection of plants to seek out
the adult stage. They can also be monitored for in their early-instar crawler phase through the use

14

of double-sided sticky tape wrapped around individual shoots. The crawlers are caught in the
sticky glue and can be counted for abundance under a dissection microscope (Polavarapu 2000).
Management of scale insects can be difficult due to their protective covering. However,
the crawlers are more susceptible to insecticide control because of their lack of scale covering
and mobility. Due to this fact, knowledge of crawler emergence and their susceptibility to
different insecticides is vital. Control methods include spraying of dormant oil in the late spring
to suffocate the immatures, as well as pyriproxifen (Esteem™), an insect growth regulator timed
to disrupt molting in the spring so that adult scales are not formed. Additionally, well-timed
applications of scale-active insecticides to target the crawler stage can reduce populations.
Regular pruning of infested branches and older shoots also suppresses populations (Marucci
1966).
Natural enemies of Putnam scale have been found. In New Jersey, nine parasitoids and
two lady beetles were found to prey on Putnam scale (Polavarapu 2000). Many parasitoids have
been found from Lecanium scale, mostly of the families Aphelinidae and Encyrtidae (Miller
1997).

JUSTIFICATION FOR RESEARCH
The lack of information regarding the life history and biology, detection and sampling methods,
insecticidal and biocontrol measures, and potential economic impact of blueberry gall midge and
scale insects in Michigan blueberries is limiting the development of integrated pest management
programs for them. While some details are known about these pests in other states, their
behavior, phenology and ecology could be different in Michigan. Information about the pests‟

15

life history and biology as well as detection and sampling methods will help growers and scouts
to know where and how to find the pests and the ideal timing of insecticides.
Blueberry gall midge is of great economic importance in Florida, where it damages floral
buds. However, floral bud damage has not been observed in Michigan. Even so, blueberry gall
midge may still have an indirect effect on plant vigor and flower bud growth. Putnam scale and
Lecanium scale, although found in localized regions of southwest Michigan, could still pose
problems to some growers that may not have robust IPM programs. If left unchecked, they have
the potential to also reduce blueberry vigor and yield.
With the diminished use of broad-spectrum insecticides such as azinphosmethyl, and the
adoption of different insecticides, populations of secondary pests are expected to increase and
could become major pests. Blueberry gall midge and scale insects are two such secondary pests
that are increasingly being observed in Michigan blueberries. Increased sightings by scouts and
growers of the pests and their damage in recent years have prompted investigations into their
biology and effective control measures. Whether or not these pests are economically important is
not known, as blueberry gall midge and lecanium scale do not attack the fruit directly, and
Putnam scale has thus far been found in very small numbers. Research was conducted to
determine if these insects do a significant amount of damage to blueberry bushes. To develop a
management plan, first the distribution and phenology of these insects must be known to
determine what areas must be targeted and the best time to apply insecticides. Pesticides that can
control these pests must then be determined. It would also be useful to know if any natural
enemies exist in the system, and their role in controlling the populations of this insect.

16

CHAPTER 2

DISTRIBUTION AND PHENOLOGY OF BLUEBERRY GALL MIDGE
(DASINEURA OXYCOCCANA) IN MICHIGAN

ABSTRACT
Blueberry gall midge is a potential pest of Michigan blueberries whose damage has recently been
sighted with increasing frequency in the state. In Florida, it causes economic damage to the
flowering buds. However, in Michigan blueberry gall midge has been found to damage only
vegetative shoots, the impact of which unknown. In this study, farms throughout Michigan were
surveyed for the presence of blueberry gall midge. Blueberry gall midge was found in 43 of the
46 surveyed farms in 11 counties. Multiple monitoring techniques, including yellow sticky traps,
emergence traps, observational sampling, and vegetative shoot dissections were used to describe
the general biology of blueberry gall midge in blueberry fields in southwest Michigan that were
known to be infested. Yellow sticky traps were not effective at catching blueberry gall midge.
Emergence traps were most useful in early detection of blueberry gall midge in April, and
observational sampling for damage symptoms and vegetative shoot dissections revealed multiple
population peaks throughout July and August. This information about the biology and
distribution of blueberry gall midge will be useful in timing control methods in the future if it
becomes an economic pest of Michigan blueberries.

17

INTRODUCTION
Blueberry farms are inhabited by beneficial insects such as pollinators and natural enemies, as
well as key pests such as cranberry fruitworm (Acrobasis vaccinii Riley), blueberry maggot
(Rhagoletis mendax Curran) and Japanese beetle (Popillia japonica Newman). In Michigan
blueberries, other major pests include leafrollers, aphids and cutworms. Pests that damage fruit
and floral structures are especially concerning because they can directly impact fruit yield and
quality. The blueberry gall midge, Dasineura oxycoccana Johnson, is one such pest that has
caused bud damage and yield reduction in rabbiteye blueberry (Vaccinium ashei Reade) (Lyrene
and Payne 1992, Dernisky et al. 2005). In recent years, personal observation and conversations
with blueberry growers, scouts and industry representatives have indicated increased numbers of
blueberry gall midge throughout Michigan farms. This increase may be due to reductions in the
use of broad-spectrum insecticides and the adoption of more selective insecticides in recent
years.

Distribution
Blueberry gall midge, described by Gagné (1989), is a small cecidomyiid fly, about 3 mm
in length, that infests and kills floral and vegetative buds of Vaccinium plants, including
blueberries and cranberries. Outside of Michigan, the midge has been recorded in blueberry
fields located in Florida, Maine, New Jersey, Wisconsin, Washington and Oregon (Mahr 1991,
Lyrene and Payne 1992, Yang 2005, Reekie et al. 2009, Tanigoshi et al. 2010). In Wisconsin and
in Cape Code, Massachusetts, this insect is known as the cranberry tipworm where it is found in
cranberry bogs (Mahr 1991, personal communication with Sunil Tewari). In Florida, it is the
major pest of blueberries, and in 1992 caused upwards of 90% death of flower buds in several

18

fields (Lyrene and Payne 1992). There is relatively little published information regarding the
biology of D. oxycocanna in northern highbush blueberry or cranberry, and it has not been
extensively studied in Michigan. Its distribution and level of infestation across the state and in
farms is unknown. Surveys of farms in Oregon in 2005 indicated its presence in 10 of 10
surveyed blueberry fields, with infestation ranging from 1% to 80% of total vegetative shoot tips
(Yang 2005).

Biology
Adult blueberry gall midges emerge from pupae in the soil and oviposit in unopened
shoot tips and the developing larvae eat tissue from the inside of the bud. The larvae develop
through three instars, the first of which is difficult to see without a high-powered microscope.
The second and third instars are small but visible to the naked eye. The third instar is about 2 mm
long and an orange-pink color. These late-instar larvae drop to the ground to pupate in the soil.
The development time of the gall midge is unknown, but it is known to have up to 11 generations
per year (Sampson et al. 2002).

Damage and symptoms
Damage by the gall midge leads to death of the apical meristem revealed by the
blackening of the bud and curling of surrounding leaves (Gagné 1989). These symptoms are
often confused with frost damage in the spring, nutrient deficiency or herbicide, fungicide or
insecticide damage. Due to these misdiagnoses and the midge‟s small size, some growers dismiss
the damage and remain unaware of the insect in their fields. However, simply unfurling a single
damaged bud often exposes multiple larvae. Damage from larval blueberry gall midge can also

19

cause a branching response in the blueberry plant with the growth of lateral side shoots. This
increased number of fruiting terminals may be beneficial to fruit yield. However, the effect of
shoot branching on blueberry production has not yet been examined (Chapter 5).
Phenological and degree day models can be useful tools to determine the ideal time for
applying management techniques (Preuss 1983, Jones 1991). For example, a model for whitemarked tussock moth (Orgyia leucostigma J.E. Smith) has been developed to assist growers by
maximizing the effectiveness of pheromone traps and insecticide applications with knowledge of
peak pest emergence (Isaacs and Van Timmeren 2009). Phenology of blueberry gall midge has
been studied in rabbiteye blueberry in Florida through the use of various monitoring techniques.
Yellow sticky traps, adult emergence, and bud and shoot tip dissections were used in blueberry
fields in Florida; although time consuming, bud and shoot tip dissections were found to be the
most effective technique (Sarzynski and Liburd 2003). Emergence traps were later tested to
determine the early emergence of the adult flies (Roubos and Liburd 2010). Presence and
phenology of the midge were also determined in Oregon and Washington using shoot tip
dissections and observations for damage (Yang 2005, Tanigoshi et al. 2010). In lowbush
blueberries, phenology was determined through the use of shoot tip dissections, trapping with
yellow sticky boards, insect sweeps and rearing (Reekie et al. 2009).
The goal of this study was to determine the severity of infestation by blueberry gall
midge in the major blueberry producing areas of Michigan and to get a better understanding of
their biology in Michigan blueberries. To improve understanding of the impact of blueberry gall
midge, the phenology, distribution and level of infestation of the insect were assessed. Surveying
for damage and presence of the midge in farms and nurseries across the state was used to
determine their distribution. Yellow-sticky traps, adult emergence traps, shoot tip dissections,

20

and rearing were tested to determine the most effective monitoring methods and to develop
phenology curves and predict peak emergence based on growing degree-days.

METHODS
Selecting surveying sites
Widespread surveying was conducted in 2009. Since the presence of blueberry gall midge within
farms and nurseries was unknown, farms were selected in the primary regions of blueberry
production with some outlier locations to ensure a wide geographic spread of sampling. The
majority of survey sites were in southwestern Michigan. In total, 46 conventionally managed
blueberry farm plots in 10 counties and 11 nursery plots in one county were surveyed (Table
2.1). The 11 nursery plots were located in four nurseries in Van Buren County. All cultivars are
listed in Table 2.2.

Table 2.1. Number of farms and nurseries surveyed for blueberry gall
midge in counties in Michigan
County
Allegan
Berrien
Genessee
Grand Traverse
Ingham
Manistee
Mason
Muskegon
Ottawa
Van Buren
Washtenaw

# of farms surveyed
6
7
2
1
1
2
2
7
8
8
2

21

# of nurseries surveyed
0
0
0
0
0
0
0
0
0
4
0

Table 2.2. Cultivars of highbush blueberry surveyed for
blueberry gall midge
Cultivar
Bluecrop
Blueray
Duke
Elliott
Jersey
Rubel
Weymouth
Unknown

# of farms
22
2
0
9
7
1
1
4

# of nursery plots
4
0
1
4
1
1
0
0

Surveying methods
One two to three acre field per farm was surveyed for blueberry gall midge infestation from midJune to mid-August 2009. Before surveying, infested shoots were sampled from the field and
inspected to ensure that blueberry gall midge larvae were present on the farm. Surveying was
conducted in each field along 10 transects spaced one bush apart. Each transect contained five
bushes spaced one bush apart. In total, 50 bushes were surveyed per field. For each observation,
the number of blackening, infested shoots was counted on the top, bottom, and side of one-half
of the bush. Due to the bush spacing and size within a planting, it was difficult to count all of the
shoots on both sides of a bush. Percent shoot infestation was calculated by dividing the number
of infested shoots by an average total number of shoots (total number of new shoots on 10 halfbushes divided by 10). Average percent infestation was calculated for each sampled field for
each weekly sample.
In the beginning of August 2009, surveys were conducted at four nurseries in blocks of
potted blueberry bushes that were two to three years of age. At three of the nurseries, three
blocks of nursery plants were surveyed. At the fourth, one block of bushes was surveyed. Since
nursery plants were arranged in large blocks of adjacent bushes, it was difficult to reach plants
more than three plants in from the edge. Only pots close to the perimeter of the blocks were
22

sampled, and 50 bushes were sampled per cultivar per nursery. The number of infested shoots
was counted on each of the sampled plants. Percent infestation on bushes was calculated by
dividing the number of infested shoots by an average total number of shoots (total number of
new shoots on 10 bushes divided by 10). Average percent infestation was calculated for each
cultivar at each sampled nursery.

Phenology of blueberry gall midge infestation
Observational sampling: In 2009, to determine the phenology of blueberry gall midge, three
blueberry fields of cultivar „Bluecrop‟ on farms in southwest Michigan with a history of
blueberry gall midge infestation were selected. Every two weeks from June 22 to September 15,
25 bushes per site were observed for damage by this pest. Sampling was done on bushes in five
transects spaced 5 rows (13.7 m) apart, with each transect containing five bushes each spaced 10
bushes (12.2 m) apart. The number of shoot tips damaged by blueberry gall midge was counted
on each bush. To determine the number of new growing shoots that could be infested, at the
beginning of the season the number of new shoots was counted on ten plants per field, and then
averaged to get an average number of new shoots per bush. Percent infestation on bushes was
calculated by dividing the number of infested shoots by an average total number of shoots.
Average percent infestation was calculated for each field.
In 2010, five different fields with known infestations of blueberry gall midge were
selected. Four fields were of cultivar „Bluecrop‟ and one of cultivar „EarliBlue.‟ Prior to the
growing season, a section of 200 bushes was flagged and reserved for observational sampling.
Once per week, from May 12 to October 14, 30 randomly selected bushes in the 200-bush field
areas were observed for damage by blueberry gall midge, and the number of damaged shoot tips

23

was counted on each of these bushes. Additionally, on 10 randomly selected bushes, the number
of vulnerable shoot tips was counted and then averaged to get an average number of susceptible
green shoots per bush. Vulnerable shoot tips were defined as young fleshy shoot tips emerging
from shoots that are elongating through the growing season. Percent infestation was calculated
by dividing the number of infested shoots by the average number of susceptible green shoots per
bush. Average percentage infestation was calculated for each field for each weekly sample.

Yellow Sticky Traps: In 2010, trapping techniques were used to monitor for adult blueberry gall
midge in the four „Bluecrop‟ blueberry fields. Prior to the research season, a 200-bush section of
each field was flagged and reserved for these studies. Three yellow sticky traps were placed
within the canopy on randomly selected bushes in the field and retrieved and replaced once per
week from June 10 to August 23. The number of blueberry gall midge found on each trap was
counted and recorded. The total number of blueberry gall midge caught was counted per week.

Emergence traps: Emergence traps similar to those of Roubos and Liburd (2010) were deployed
within the same 200-bush fields as were sampled for blueberry gall midge damage, described
above. Traps were constructed from 2.5 qt plastic paint buckets (Home Depot, Atlanta, GA) and
clear 10 cm diameter Petri dishes (Figure 2.1). Tanglefoot glue applied with a spatula to the
inside of the Petri dish was used as an adhesive to capture emerging blueberry gall midge adults.
Traps were placed on six randomly selected bushes in the four fields, positioning them next to
the crown of the plants, within 30 cm of the base. Bush rows ran south to north at two farms, and
west to east at two farms. At the farms with bushes running south to north, traps were placed on
the east and to the west of the bushes, while at the farms with bushes running west to east, traps

24

were placed on the south and north of the bushes. Each week, these emergence traps were
retrieved and replaced, and the number of blueberry gall midge adults trapped in the Petri dish
was counted.

Figure 2.1. Emergence trap used to capture adult midges. The trap is comprised of a
bucket with the bottom removed, covered with a large Petri dish that has tanglefoot glue
smeared on the inner surface. For interpretation of the references to color in this and all
other figures, the reader is referred to the electronic version of this thesis.

Shoot dissections: Shoots were collected from the same four blueberry fields for dissection.
Thirty shoots were collected from 30 randomly selected bushes in the 200-bush fields each week
from May 12 to September 29, then placed in a plastic bag and in a cooler containing ice. Shoots
were randomly selected from the top third, middle third, or bottom third of each sampled bush.
Shoots were not inspected beforehand to determine if they were infested. Within 24 hours, these

25

shoots were brought back to the laboratory and dissected with forceps and inspected under a
st

microscope to determine the number of eggs, 1 , 2

nd

rd

and 3 instar larvae and pupae. The color

of the vegetative bud (green, black, or mottled) was also recorded to determine whether color
may be used as a crude assessment of damage caused by blueberry gall midge damage.
An estimate of the number of larvae per bush was calculated by multiplying the average
number of larvae found per week in the shoot dissections and the average number of shoot tips
per bush from the observational samples.

Degree day-based phenology
To determine the phenology of blueberry gall midge based on degree day accumulation, growing
degree days were calculated for peak activity as determined by the 2009 and 2010 observational
sampling and shoot dissection data. Dates of peak infestation and adult emergence were
determined, and accumulated growing degree days were found using the Enviroweather
Automated Weather Station Network (http://www.agweather.geo.msu.edu/mawn/). The closest
weather stations to the farms were used to calculate the growing degree days. These were the
Benton Harbor, Grand Junction and South Haven stations. Growing degree days were calculated
from March 1 using the Baskerville-Emin method with a base temperature of 50 ˚F.

Statistical analysis
All analyses were conducted using JMP 8.0.2 (SAS, Cary, NC). Percentage of shoots infested
with blueberry gall midge was plotted for each surveyed farm and nursery. The percent
infestation in all farms was compared to the percent infestation in all nurseries using a Student‟s
t-test.
26

Infestation data: For the data gathered in 2009 and 2010, the percent infestation in all sampled
farms was averaged for each week. For the 2010 data, the percent infestations within the top,
middle and bottom third of the bush were also averaged across all sampled farms. The number of
vulnerable shoots each week was also plotted. Percent infestation was compared among the three
parts of the bush using one-way analysis of variance and separation of means with Tukey‟s
Honestly Significant Difference test.

Emergence traps: Data from farms with North-South rows were used to compare the number of
midges captured on the east aspect of the rows and the number of midges found on the west
aspect. Similarly, the number of midges found on the north aspect was compared to the number
of midges found on the south aspect. Data was separated and analyzed by month. This was done
by fitting the Poisson distribution to the data and a likelihood ratio Chi-Square test.

Shoot tip dissections: The average number of larvae per shoot was calculated, and phenology
curves were drawn. The average number of larvae was compared among each color category of
vegetative bud using one-way analysis of variance and means separation with Tukey‟s HSD
(JMP 8.0.2, Cary, NC).

RESULTS
Surveys for blueberry gall midge
There was higher percent infestation by blueberry gall midge in nurseries than in farms
(t(13)=3.43, P < 0.005). Blueberry fields varied widely in the level of blueberry gall midge
infestation, from one field at a farm in Ingham County with no infestation to an average of 17%
27

infestation in Muskegon county (Table 2.3 and Figure 2.2). The average percent infestation
(±S.E.) of all farms was 8.3 ± 1.6. At blueberry nurseries, infestation levels were generally
higher than at farms (Table 2.4 and Figure 2.3), with 25.7 ± 4.5 average percent infestation
across all nurseries. There was little evidence of significant variation in infestation levels by
cultivar (Table 2.4). There was considerable variability in average percent infestation (Tables 2.3
and 2.4).

Table 2.3. Average percent infestation of shoots (±S.E.) by blueberry gall
midge infestation in Michigan blueberry farms, by county
County
Allegan
Barry
Berrien
Genesee
Grand Traverse
Ingham
Manistee
Mason
Muskegon
Ottawa
Van Buren
Washtenaw
All farms

Number of farms surveyed
7
1
7
2
1
1
2
2
6
6
9
2

Percent infestation
8.5 ± 3.0
4.5 ± 0.0
14.3 ± 6.6
4.9 ± 0.8
13.5 ± 0.0
0.0 ± 0.0
1.3 ± 1.3
0.1 ± 0.1
17.0 ± 4.2
7.9 ± 5.3
6.1 ± 1.7
5.1 ± 5.1
8.3 ± 1.6

Table 2.4. Average percent infestation (±S.E.) by blueberry gall
midge at Michigan blueberry nurseries, by cultivar

Cultivar
Bluecrop
Duke
Elliott
Jersey
Rubel
All nurseries

Number of nurseries surveyed
4
1
4
1
1

28

Avg percent
infestation
20.1 ± 4.2
26.3 ± 0.0
30.9 ± 11.9
20.1 ± 0.0
30.4 ± 0.0
25.7 ± 4.5

Figure 2.2. Average (± S.E.) percent infestation of Michigan blueberry farms by blueberry gall
midge. Bars following county name differentiate individual surveyed farms within a county.

29

80

Percent infestation

70
60
50
40
30
20
10
0
1A

1B

1C

2A

2B

2C

3A

3B

4A

4B

4C

Nursery plot
Figure 2.3. Percent infestation of blueberry gall midge (± S.E.) in Michigan blueberry
nursery plots. Numbers 1-4 indicate different nurseries. Letters A, B, and C indicate
different surveyed plots within nurseries.

Observational sampling for blueberry gall midge phenology
In 2009, a peak of infestation was found on July 30 (Figure 2.4), when an average of 6.5 ± 1.4
shoots showed signs of infestation. In 2010, multiple peaks of infestation were found June, July
and August, with the largest (68% of green tips) occurring July 15 (Figure 2.5), with an average
percent infestation of all green tips of 67.6 ± 13.4. The average number of vulnerable shoot tips
available for infestation by blueberry gall midge was 35 ± 4.8 in the beginning of the growing
season in May, and sharply decreased at the beginning of June to an average of one to three
vulnerable shoot tips (Figure 2.7). The levels of infestation in the top, middle and bottom third of
the bush show the same timing of the peaks of infestation (Figures 2.6 and 2.8)

30

9

Percent infestation

8
7
6
5
4
3
2
1
0
6/22

7/6

7/20

8/3

8/17

8/31

9/14

Percent infestation

Figure 2.4. Variation in percent infestation (± S.E.) of new shoots by blueberry gall midge
at Michigan farms during 2009. The number of growing new shoots was counted at the
beginning of the growing season.

90
80
70
60
50
40
30
20
10
0
4/15

5/6

5/27

6/17

7/8

7/29

8/19

9/9

9/30

Figure 2.5. Variation in percent infestation (± S.E.) of elongating shoot tips by blueberry
gall midge at Michigan farms during 2010. The number of vulnerable shoot tips was
counted each week.
31

Top
100
80
60
40

Percent of shoot tips that are infested

20
0
4/15

5/15

6/15

7/15

8/15

9/15

8/15

9/15

8/15

9/15

Middle
100
80
60
40
20
0
4/15

5/15

6/15

7/15

Bottom
100
80
60
40
20
0
4/15

5/15

6/15

7/15

Figure 2.6. Variation in the percent infestation (± S.E.) on the top, middle and bottom third
of blueberry bushes at Michigan farms during 2010.

32

Number of vulnerable shoots

45
40
35
30
25
20
15
10
5
0
5/12

6/12

7/12

8/12

9/12

Number of vulnerable shoots

Figure 2.7. Variation in the number of vulnerable shoot tips (± S.E.) on blueberry bushes at
Michigan farms during 2010.

25
20
15

Bottom
Middle

10

Top

5
0
5/12

6/12

7/12

8/12

9/12

Figure 2.8. Variation in the number of vulnerable shoot tips (± S.E.) in the top, middle, and
bottom third of blueberry bushes at Michigan farms during 2010.

33

Yellow sticky traps
Only seven blueberry gall midge adults were caught on yellow sticky traps (Figure 2.8) in 2010.
Blueberry gall midge adults were trapped on yellow sticky traps from June 10 to July 23.
Captures were low using this method, with these seven samples detected across 5 farms and 3
traps deployed each week for three months. Specimens were caught at four of the five farms.

Total number of of BGM

3

2

1

0
6/10

6/15

6/28

7/12

7/28

8/9

Figure 2.9. The total number of blueberry gall midge caught on yellow sticky traps placed
in infested blueberry fields in 2010.

34

Emergence traps
Using emergence traps placed over soil under bushes, the first catch of a blueberry gall midge
adult was on April 22, 2010, with peaks of emergence on May 24, July 5, and August 3 (Figure
2.9). When comparing aspects of the soil on which the traps were placed. In most months, aspect
had no significant effect on blueberry gall midge captures. However, the east-west aspect had a
significant effect on blueberry gall midge captures in the month of August, with a higher number

Total number of BGM

of catches on the west aspect of the plant (χ = 4.37, df = 1, P = 0.04) (Table 2.5).

35
30
25
20
15
10
5
0

Figure 2.10. The total number of adult blueberry gall midge caught in emergence traps
during 2010.

35

Table 2.5. Average number of adult blueberry gall midge (±
S.E) caught in emergence traps at the east, west, north and
south aspects at four fields on six randomly selected bushes
during each month in 2010.
Month
Soil aspect
Avg. number of BGM
April
E
0.04 ± 0.04
W
0.0 ± 0.0
N
0.0 ± 0.0
S
0.04 ± 0.04
May
E
0.11 ± 0.07
W
0.20 ± 0.18
N
0.10 ± 0.05
S
0.13 ± 0.07
June
E
0.17 ± 0.09
W
0.36 ± 0.15
N
0.08 ± 0.04
S
0.08 ± 0.04
July
E
0.44 ± 0.26
W
0.33 ± 0.14
N
0.16 ± 0.09
S
0.02 ± 0.02
August
E
0.03 ± 0.03
W
0.25 ± 0.12
N
0.04 ± 0.03
S
0.08 ± 0.05

Shoot tip dissections
There were multiple peaks of larval infestation in the dissected shoots, from June through August
2010. The largest peak of larval infestation was on July 15 (Figure 2.10). First instar larvae were
nd

present throughout the season and reached a peak in June. The number of 2

rd

and and 3 instar

larvae was lower in May and increased later through the season until late-August (Figure 2.11).
There were significantly more blueberry gall midge larvae found in mottled and green shoot tips
than in the black shoot tips (F = 4.33, df = 2,57, P = 0.018) (Figure 2.12). The estimated number
of larvae per bush was highest on June 6, 2010, with 32.6 ± 23.2 larvae per bush (Figure 2.13).
This number steadily decreased until the end of sampling.

36

Growing Degree Days
st

From the 2009 observational sampling data, growing degree days from March 1 to the largest
peak of adult emergence was 1383 at a base temperature of 50 ˚F. From the 2010 observational
sampling data, growing degree days to the largest peak of emergence was 1317 at a base
temperature of 50 ˚F. Growing degree days to the largest peak of larval infestation in 2010 was

Avg # of larvae per shoot tip

1369 at a base temperature of 50 ˚F.

8
7
6
5
4
3
2
1
0

Figure 2.11. Variation in the number of blueberry gall midge larvae (± S.E.) from
dissections of shoots collected at infested blueberry fields in 2010.

37

14

3rd instar

12

2nd instar

10

1st instar

8
6
4
2

Figure 2.12. The number of blueberry gall midge larvae found in shoot tips of blueberry
shoots, separated by instar.

Avg # of larvae per shoot tip

8
7
6
5
4
3

2
1
0
Black

Mottled

Green

Figure 2.13. Average (± S.E.) number of blueberry gall midge larvae found in shoot tips of
differing colors.
38

9/28

9/11

8/31

8/23

8/16

8/10

8/3

7/29

7/21

7/13

7/5

6/29

6/21

6/15

6/8

6/1

5/25

0
5/18

Avg # of larvae pershoot tip

16

60

Larvae per bush

50
40
30
20
10
0
5/12 5/26

6/9

6/23

7/7

7/21

8/4

8/18

9/1

9/15

Figure 2.14. Estimate of the number of blueberry gall midge larvae per bush (± S.E.) in
2010.

DISCUSSION
Blueberry gall midge was present in almost all of the surveyed farms and in all of the
surveyed nurseries. This was also true in Washington state, where a smaller survey of 21 farms
was conducted (B. S. Gerdeman, personal communication). There was also a significantly higher
percent infestation in nurseries than in farms. This is most likely due to the increased prevalence
and encouragement of new shoot growth in nurseries compared to established blueberry farms. It
may also be a reflection of the lower level of insecticide use in nurseries, as a result of these sites
not requiring protection of fruit from insect pests. The high infestation rate within nurseries
would facilitate introduction and dispersion of blueberry gall midge to farms in the state and
country that buy bushes from nurseries.
39

Infestation levels also varied considerably among farms and nurseries sampled. Blueberry
gall midge has multiple generations and peaks of emergence during the growing and harvesting
seasons. Since this surveying was conducted over a period of two months, surveying days may
have been concurrent with a range of midge emergence and infestation, resulting in the observed
variability. Additionally, during some of the late surveying dates in July and August, there was
little to no new shoot growth on the bushes, and fewer reproduction sites for blueberry gall
midge.
The earliest catch of blueberry gall midge in 2010 was on April 22, just before bud-break,
using the emergence trap sampling method. Peaks of emergence and infestation occurred through
July and August. In Florida, where blueberry gall midge is an economically important pest of
rabbiteye blueberry, initial catch was as early as January 14, with peaks of adult emergence on
March 21 (Roubos and Liburd 2010). There, the growing and harvest season are much earlier
than in Michigan. In lowbush blueberries in Nova Scotia, blueberry gall midge larvae were
present in high levels through July and August (Reekie et al. 2009). The estimated number of
larvae per bush was highest in early June, and even with low numbers of larvae per shoot, the
high number of growing shoot tips offered the adults numerous reproduction sites. As the season
progressed, the number of shoot tips decreased, but the number of larvae per shoot tip increased.
This allowed blueberry gall midge to maintain steady populations between 10 and 20 larvae per
bush until August. With individual blueberry fields containing hundreds of bushes, there may be
thousands of blueberry gall midge. At the beginning of the growing season, there is a large flush
of new growth and occasional flushes of growth at varying times during the season, depending
on the rainfall conditions. If there were to be a large flush of growth later in the season, adult
midges would have the reproductive sites needed to quickly establish high populations.

40

During my sampling, all monitoring methods except for the yellow sticky traps indicated
greater infestation by blueberry gall midge in July than in other months. However, at that time,
there was a very small amount of vulnerable tissue compared to the beginning of the growing
season in May. The yellow sticky traps were not an effective method for trapping blueberry gall
midge, possibly because they were not close enough to the vegetative shoots, or because they
were not placed on heavily infested bushes. The flies may also not be attracted to yellow.
Emergence traps had more adult catches than yellow sticky traps, and were the first monitoring
technique to detect adult midges during the season. Although some of these traps were destroyed
by harvesters and sprayers, they could still prove to be an effective method for growers to
determine the initial emergence of this pest in the spring to help identify when to protect bushes
from this pest.
There was a significantly higher catch in the emergence traps placed on the west aspect
of bushes in August. This could indicate that blueberry gall midge pupal survival is better when
the sun is heating the soil later in the day. All blueberry gall midge caught in August were caught
in five individual traps, pointing to within-field variability.
Vegetative shoot dissection was an effective method to determine the number of
blueberry gall midge larvae present, and was the quickest way to confirm the presence of gall
midge in a field. However, growers are unlikely to adopt shoot dissections to look for eggs and
early-instar larvae because it is time consuming and requires a high-power microscope. This
method helps to pinpoint an ideal time to target the larval stage of the blueberry gall midge, and
may be a useful method for consultants and extension agents to help identify infestations. The
rd

pink 2-mm 3 instar larvae are easy to spot with a hand lens, but they are not common until late
in the season. Additional research to examine the relationship between temperature accumulation
41

and infestation may provide a more practical way to identify risk periods from this pest.
Knowing the initial peak times of larval infestation will be useful in conjunction with the use of
insecticides effective at controlling blueberry gall midge. Many blueberry farms apply multiple
insecticide treatments at different times of the season to control blueberry maggot, cherry
fruitworm and Japanese beetle. At all monitored farms, insecticide sprays were applied days
before peak larval infestation and adult emergence. It is possible that some of these sprays are in
fact controlling blueberry gall midge, but that their numbers are so high that they are able to
repopulate within a short period of time. Since no unmanaged fields were monitored in this
study, whether or not this is true is unknown.
The growing degree days calculated from the Enviroweather weather stations can be used
to determine peak blueberry gall midge activity for targeting it with control measures. The
growing degree days corresponding with the largest peak of adult emergence in 2009 and 2010
were around 1300; a third year of growing degree day data and additional studies in controlled
growth chambers would be useful to determine a more accurate estimate. These studies on
blueberry gall midge biology and monitoring will aid in the development of a management plan
for blueberry gall midge.

42

CHAPTER 3

BIOLOGICAL AND CHEMICAL CONTROL OF BLUEBERRY GALL MIDGE
(DASINEURA OXYCOCCANA) IN MICHIGAN BLUEBERRIES

ABSTRACT
Blueberry gall midge, Dasineura oxycoccana (Johnson) is a potential pest of Vaccinium crops,
including blueberry and cranberry, in Michigan. Although insecticide-based management may be
able to control key pest species, use of broad-spectrum pesticides could additionally decrease
natural enemy populations, leading to pest outbreaks. To evaluate new insecticides for control of
blueberry gall midge, a laboratory bioassay was conducted using infested shoots and a Potter
spray tower to apply acetamiprid, cyazypyr, methomyl, phosmet or spirotetramat. A field trial
was also conducted to compare the efficacy of acetamiprid, cyazypyr, cypermethrin, methomyl,
phosmet, spinetoram, spirotetramat. In the bioassay, all of the insecticides were effective at
killing blueberry gall midge, whereas in the field trial, none of the insecticides significantly
reduced the level of infestation. Parasitoids and natural enemies of blueberry gall midge were
surveyed at field sites using shoot tip dissection and observational sampling. Shoots were also
collected to allow for adult midge and parasitoid emergence. Although no natural enemies were
found through observational sampling, shoot tip collection for rearing of parasitoids yielded
eight Apostocetus and one Platygaster, and shoot tip dissections yielded two specimens of
Synopeas synopeas.

43

INTRODUCTION
Blueberry gall midge, Dasineura oxycoccana (Johnson) is a pest of blueberries in Florida
(Lyrene and Payne 1992). Information gathered from scouts, growers and personal observations
indicate that its population in Michigan blueberries is increasing. Midges are small flies of the
family Cecidomyiidae, and gall wasps in this group induce the creation of gall tissues in their
host plants. One of the most damaging gall midge pests in North America is the Hessian fly,
Mayetiola destructor, an invasive species that infests cereal crops. The Hessian fly has caused
yield reductions of up to 50% of dry matter yield of red winter wheat (Buntin and Raymer 1989).
Blueberry gall midge, which attacks and kills the flowering and vegetative buds of growing
shoots, has been cited as one of the most damaging pests of rabbiteye blueberries (Vaccinium
ashei Reade) in Florida, causing up to 90% mortality in flowering buds (Lyrene and Payne 1992)
and it is known to affect cranberry (Vaccinium Macrocarpon) as well. It has a rapid generation
time; larvae remain in buds for one to two weeks before pupating. The larvae feed on plant
juices, damaging the shoot tip meristematic tissues, and their damage becomes visible as dark
shoot tips 7-12 days after infestation. The impact of the fly‟s increase in population and its
biology in the main blueberry production region of Michigan is unknown.
Observations by growers and scouts have indicated that secondary pests such as
blueberry gall midge have recently increased in abundance in Michigan blueberries. This could
be a response to the reduced use of broad-spectrum insecticides such as azinphosmethyl in
preparation for banning of the use of this product in 2012 and the development of IPM programs
relying on new selective insecticides. This larger population of blueberry gall midge has resulted
in high levels of damage to young vegetative shoot tips, which can induce lateral branching
similar to witches‟ broom (Tanigoshi et al. 2010).

44

Although the economic impact of blueberry gall midge is not yet known in Michigan (see
Chapter 4), if it is found to be economically damaging, it would be valuable to have developed
effective control measures. Non-insecticidal methods of controlling blueberry pests such as mass
trapping with pheromone traps, reliance on biological control agents, and use of resistant
cultivars are not commonly employed in commercial blueberry farms in Michigan. To reduce the
frequency of pesticide application, it would be useful to know whether current spray programs
targeting major blueberry pests such as blueberry maggot and Japanese beetle will provide some
control of blueberry gall midge. Although spray programs are able to eliminate pest species, they
can also have detrimental effects on the pests‟ natural enemies (Croft and Brown 1975; Theiling
and Croft 1988), and may have significant sub-lethal effects on hymenopteran parasitoids
(Williams et al. 2003; Desneux et al. 2007).
Insecticide treatments for control of blueberry gall midge in blueberries have been
evaluated in Mississippi, Florida, and Washington. In Mississippi, bench-top bioassays found
that phosmet and spinosad cause approximately 50% mortality of larvae in bud galls. Malathion
was found to be very effective, killing 94% of larvae in treated bud galls (Sampson et al. 2002).
Field insecticide trials in Florida found a significant decrease in blueberry gall midge larval
infestation in bushes treated with diazinon or malathion (Finn 2003). In a field insecticide trial
conducted in Washington blueberries, spirotetramat and cyazypyr were found to reduce levels of
blueberry gall midge larvae (Tanigoshi et al. 2010). In cranberries, azinphosmethyl and phosmet
were found to control blueberry gall midge (Mahr 2005).
Parasitoids of blueberry gall midge were studied in Mississippi rabbiteye blueberries
(Sampson et al. 2006). Three platygastrids of the genera Synopeas, Platygaster and Inostemma
and one Eulophid of the genus Aprostocetus were collected from midge larvae and described. No

45

information of blueberry gall midge parasitoids is available in populations in the Midwest.
Although insecticide studies have been conducted (Sampson et al. 2002, Tanigoshi et al. 2010),
many pesticides remain to be tested. Here, I study the effect of various insecticides on blueberry
gall midge damage in lab bioassays and a field trial. Parasitoids affecting blueberry gall midge
were also collected to determine the potential for biological control of this pest.

METHODS
Bioassay
A bioassay was performed using 400 shoot tips infested with blueberry gall midge collected
from six untreated rows (~1/10 acre) of highbush blueberry cultivar „Bluecrop‟ at the Southwest
Michigan Research and Education Center in Benton Harbor, MI. This mature planting is located
in sandy soil in Berrien County, Michigan. The bioassay was conducted at the Trevor Nichols
Research Complex in Fennville, MI on a still, calm day. The experimental design consisted of
eight treatments (Table 3.1), and 10 replicates, each containing five shoots tips infested with
blueberry gall midge that were placed on a Petri dish. A Potter Spray Tower was used to apply
the insecticide to the dishes. The shoot tips were then flipped and treatments reapplied to ensure
coverage of insecticide.

Table 3.1. List of insecticides used for the bioassay of blueberry gall midge.
Treatment
water control
acetamiprid
cyazypyr
cypermethrin
methomyl
phosmet
spinetoram
spirotetramat

Trade name
Assail
Cyazypyr
Mustang Max
Lannate
Imidan
Delegate
Movento
46

Rate per acre
5.3 oz
10.0 oz
4.0 oz
3.0 pt
1.33 lb
3.0 oz
8.0 oz

Treatments (Table 3.1) consisted of one rate of acetamiprid 30SG (Assail 30SG at 5.3
oz/acre), cyazypyr 10SE (10 oz/acre), spinetoram (Delegate 25WG at 3 oz/acre), phosmet
(Imidan 70 WP at 1.33 lbs/acre), methomyl (Lannate 2.4LV 3 pt/acre), spirotetramat (Movento
2SC at 8 oz/acre), cypermethrin (Mustang Max 0.8EC at 4 oz/acre), and a control of water. All
treatments were applied to shoots on June 23, 2010 using a Potter spray tower.
After insecticides were applied, shoot tips were transferred to non-vented Petri dishes
layered with filter paper and a 1-inch diameter circle of fine sand as a pupation substrate. All
dishes were kept at room temperature for two weeks until all blueberry gall midges had emerged.
Water from a spray bottle was used to keep the samples moist. All blueberry gall midge adults
were allowed to emerge, and were then collected and counted.

Field insecticide trial
This study was performed in three untreated rows of highbush blueberry bushes cultivar
„Bluecrop‟ at the Southwest Michigan Research and Education Center in Benton Harbor, Berrien
County, MI. This planting is established in sandy loam soil. The experimental design consisted
of five treatments (Table 3.2), with four replicates arranged in a completely randomized design.
Each replicate contained 13 bushes, one bush for each of the treatments with one buffer bush in
between treatments. The rows were 10 feet apart and each bush was 4 feet apart within rows.
Treatments, listed in Table 3.2 were applied on May 4, May 19, June 1, and June 16 in
2010 on sunny, low-wind days using a CO2 backpack sprayer (R&D Sprayers) equipped with a
single TeeJet nozzle. By May 4, no visible sign of blueberry gall midge damage was apparent.
However, the insect was caught in an emergence trap earlier that week, prompting the start of
treatment applications. They consisted of one rate of acetamiprid (Assail 30SG at 5.3 oz/acre),

47

cyazypyr 10SE (20.5 oz/acre), phosmet (Imidan 70WP at 21.3 oz/acre), and two rates of
spirotetramat (Movento 2SC at 5 oz/acre and 8 oz/acre) and water as a control.

Table 3.2. List of insecticides used for the field insecticide
trial of blueberry gall midge.
Treatment
Water/Control
acetamiprid
cyazypyr
phosmet
spirotetramat
spirotetramat

Trade name
Assail
cyazypyr
Imidan
Movento
Movento

Rate per acre
5.3 oz
10.0 oz
1.33 lb
5.0 oz
8.0 oz

Plots were sampled on the Mondays or Tuesdays following treatment on May 10, May
17, May 24, June 1, June 8, June 15, June 22. During sampling, each bush was examined for
damage and the number of damaged shoots and the number of elongating green shoots was
counted. The proportion of infested shoots in each treatment was calculated.

Survey for natural enemies and parasitoids
In 2010, once every week from the beginning of the growing season until the end of August,
shoot tips were collected at each of five blueberry fields with a history of infestation by
blueberry gall midge, located in Berrien and Van Buren counties in Michigan. Four of these
fields were at conventionally managed blueberry farms. Three of these contained blueberries of
the cultivar „Bluecrop.‟ One of them contained blueberries of the cultivar „Earliblue.‟ The fifth
blueberry field was at the Southwest Michigan Research and Extension Center located in Benton
Harbor, MI, and was also of the cultivar „Bluecrop.‟ At each of these fields, a 200-bush block of
blueberries was flagged at the beginning of the growing season. Each week, up to 30 growing,
green shoot tips were selected from randomly chosen bushes. If these bushes did not have any
48

shoot tips, a shoot tip was selected from an adjacent bush. Some weeks, there were very few or
no green shoot tips found. Shoot tips were placed in a one quart Ziploc® plastic bag and
immediately placed into a cooler to prevent larval emergence.
In the laboratory one day after collection, the shoot tips were removed from the plastic
bag and placed into non-vented Petri dishes layered with moist filter paper and with a small
circle of fine sand as a pupation substrate. Each Petri dish contained up to five shoot tips. Any
remaining larvae that had emerged from the shoot tips were removed from the bags and placed
onto a Petri dish with filter paper and sand. The Petri dishes were held in the laboratory at 22˚ C
and 25% humidity; to prevent desiccation, every one to two days, the Petri dishes were misted
with water, taking care to prevent larvae from escaping. After the shoot tips were in the Petri
dishes for one week, they were removed to reduce mold. Petri dishes were inspected for larvae
and pupae using a high-powered dissection microscope. Adult blueberry gall midge and
parasitoids were allowed to emerge about two to three weeks after shoots were placed into the
Petri dishes. The number of adult midges and parasitoids was counted, and parasitoids were
collected and shipped to Dr. Blair Sampson for identification.
During observational sampling for shoot tip damage (Chapter 2) at five sites each week,
interactions between natural enemies and infested shoots were recorded. Any syrphid flies, lady
beetles, and parasitoids were noted. Observations examined 30 bushes and typically took 30
minutes. Also, during shoot tip dissections (Chapter 2), any parasitoids found were collected and
reserved for identification.

49

Statistical Analysis
Data from the laboratory bioassay were used to compare the number of emerged adult midges
among treatments. The average number of blueberry gall midge per replicate Petri dish was
square root transformed and compared among treatments using the Wilcoxon rank-sum test (JMP
8.0.2, Cary, NC). Data from the field insecticide trial was used to compare the proportions of
infested shoots among treatments. The proportions were arcsin transformed and compared
among treatments using analysis of variance (JMP 8.0.2, Cary, NC). Values for parasitoids and
other natural enemies were too low for statistical analysis.

RESULTS
Bioassay
When treated in the bioassay, significantly fewer blueberry gall midge emerged in the insecticide
2

2

treatments when compared to the control (Table 3.3) (χ = 35.1, df = 7, P > χ = 0.0001). There
were no differences among insecticides in the number of gall midge that emerged, although there
was low survival in the cyazypyr treatments compared with no survival in the other insecticide
treatments. These results show that all insecticide treatments have activity on blueberry gall
midge under these controlled conditions.

50

Table 3.3. Average number of blueberry gall midge
adults emerging (± S.E.) after treatment with
different insecticides. Values followed by the same
letters were not significantly different.
Treatment
water/control
acetamiprid
cyazypyr
cypermethrin
methomyl
phosmet
spinetoram
spirotetramat

# of D. oxycoccana
2.1 ± 1.3 A
0.0 ± 0.0 B
0.3 ± 0.2 AB
0.0 ± 0.0 B
0.0 ± 0.0 B
0.0 ± 0.0 B
0.0 ± 0.0 B
0.0 ± 0.0 B

When insecticides were compared under field conditions, there were no significant differences
among treatments at any sampling date (Table 3.4). There were no strong trends in the data that
suggest any of the treatments would control blueberry gall midge. There was no significant
difference between the treatments and the controls on the 6/1 sampling date (F = 0.52, df = 5,18,
P = 0.76) and the 6/22 sampling date (F = 0.48, df = 5,18, P = 0.79).
There were no natural enemies found through observational sampling. The shoot
collection for adult emergence yielded nine parasitoids of the family Eulophidae. Eight of them
were female Apostocetus and one was a male Platygaster, the species of which are not described
yet. Two Synopeas synopeas parasitoids were found during the shoot dissections (Chapter 2),
from collected on 7/13/2010.

51

Table 3.4. Average (± S.E.) proportion of susceptible shoots infested with blueberry gall midge per bush as a function of
insecticide treatments applied during the spring of 2010. There was no significant difference between the treatments and the
controls on any sampling date.

Treatment

Rate per
acre

5/10

5/17

5/24

6/1

6/8

6/15

6/22

Vulnerable shoots
per bush

12.5 ± 1.4

9.6 ± 0.8

9.8 ± 0.9

2.3 ± 0.3

1.1 ± 0.4

0.2 ± 0.1

3.2 ± 0.6

Water/control

0

0

0

0.5 ± 0.2

0

0.2 ± 0.2

0.4 ± 0.2

Acetamiprid

5.3 oz

0

0

0

0.2 ± 0.1

0.1 ± 0.1

0

0.8 ± 0.1

Cyazypyr

20.5 oz

0

0

0

0.4 ± 0.2

0

0

0.5 ± 0.2

Phosmet

1.33 lb

0

0

0

0.2 ± 0.1

0.2 ± 0.2

0

0.5 ± 0.2

Spirotetramat

5 oz

0

0

0

0.1 ± 0.1

0.1 ± 0.1

0

0.5 ± 0.3

Spirotetramat

8 oz

0

0

0

0.2 ± 0.2

0.1 ± 0.1

0

0.7 ± 0.2

52

DISCUSSION
Our findings indicate that insecticides provided significant control of blueberry gall
midge larval development into adults in the laboratory bioassay, but not in the field. Insecticides
were chosen from a range of chemical classes that have different modes of action, all requiring
contact or ingestion. All of the insecticides in the bioassay reduced adult emergence from
infested shoots, providing high or complete control of larval development to pupae. This assay
allowed us to determine the insecticides‟ activity under a controlled setting when blueberry gall
midge was most abundant while eliminating the effects of drift and rain that could affect
insecticide efficacy in the field.
It is difficult to judge the effectiveness of the insecticides from the field trial. Although
there were no significant effects of treatment, this could have been due to several factors. The
blueberry bushes used were not pruned in 2009, and thus produced few susceptible green shoots
in 2010. Pruning controls for plant growth and also encourages new cane development and
allows for increased photosynthesis (Gough 1994). On each sampling date, each bush had
between zero and three susceptible vegetative shoots, which affected our ability to measure
differences among treatments. This lack of resources would cause the plot to be a poor refuge for
blueberry gall midge reproduction. Fields at other locations had a greater number of vegetative
shoots at the same time as the trial. Although Chapter 2 indicates a high number of susceptible
shoots through May and early June, this was not the case at this particular site. Additionally, the
blueberry gall midge is an insect that has multiple overlapping generations throughout the
season. Since the bushes were treated with a foliar application of insecticides once every two
weeks, adults could have emerged from pupae in the ground and infested shoots after pesticide

53

residue had diminished. Future studies should be timed with periods of greatest infestation, using
the monitoring techniques used in Chapter 2 to focus on proper application timing.
In Washington State, a foliar efficacy trial was run in which a greater number of replicate
bushes were included in each treatment, and the number of blueberry gall midge larvae was
assessed every four days after treatment (Tanigoshi et al. 2010). They found significant
decreases in larval abundance in bushes treated with cyazypyr and spirotetramat at both nine and
13 days after treatment. However, sampling at further dates showed no significant differences
among treatments. In Florida, diazinon and malathion were found to be effective insecticides
(Finn 2003). In both of these studies, insecticide applications were done once populations of
blueberry gall midge were established, and these results indicate that conventional and reducedrisk insecticides can provide some short-term control of blueberry gall midge. In these studies,
entire bushes were treated, targeting the adults and larvae. Treatments targeting the pupae in the
soil have not been tested. Winter sanding of blueberry beds has been shown to reduce the
number of first generation adult midges (Mahr 1990). Additionally, cultivar resistance to
blueberry gall midge has not been investigated.
While we found no natural enemy interactions through observational sampling, nine
parasitoids were found from the adult emergence in Petri dishes and two more were found
through the shoot dissections described in Chapter 2. While identifying the parasitoids collected
in Michigan, Blair Sampson (USDA-Poplarville) noted that they were almost twice the size of
blueberry gall midge parasitoids of the same genus in Mississippi. He also noted that the larvae
and adult midge samples from Michigan were larger than those found in Mississippi. The
parasitoid complex in Michigan is similar to that of the complex in Mississippi, with Synopeas,

54

Platygaster, and Synopeas species all occurring in blueberry gall midge both states (Sampson et
al. 2006).
In Mississippi blueberry nurseries, percent parasitism by parasitoids of the genus
Platygastridae reached up to 40 % immediately after peaks of blueberry gall midge larval
infestation during flower and vegetative bud development (Sampson et al. 2006). This rate was
considered very high, but could be due to the nature of blueberry nurseries, with many
vigorously growing plants in a small space. Nurseries also receive little to no insecticide
treatments compared to conventional farms. The low rate of parasitism on Michigan blueberry
farms could be attributed to the low survival rate of midges. The low number of midges collected
in this study may not have been sufficient to detect parasitoids. Future studies should increase the
sampling size of midge larvae and use more refined methods of adult midge and parasitoid
rearing to calculate percent parasitism.
To avoid killing natural enemies and parasitoids, knowledge about their life cycle and
biology is crucial to avoid injury from insecticide application. With the lack of information
regarding parasitoids and natural enemies of blueberry gall midge in Michigan blueberries, and
the low numbers of parasitoids found thus far, it is difficult to recommend when insecticide
sprays should be applied to prevent blueberry gall midge infestation without harming parasitoids.
Although blueberry gall midge parasitoid numbers were found to be low in Michigan, it is
encouraging to know that they are present despite the reliance on chemical control. If blueberry
gall midge is found to be economically damaging, it would be wise to make efforts to conserve
natural enemy and parasitoid populations to avoid the need for application of chemical
insecticides.

55

Chapter 4

ECONOMIC IMPORTANCE OF BLUEBERRY GALL MIDGE IN HIGHBUSH
BLUEBERRIES

ABSTRACT
Blueberry gall midge, Dasineura oxycoccana, is a potential pest of blueberries in Michigan that
has damaged blueberries in Florida, destroying up to 90% of all flower buds in some fields.
Economic damage from blueberry gall midge in southern US states is estimated to be over $20
million annually. Although it attacks blueberry flower buds in Florida, it has only been found in
vegetative blueberry shoots in Michigan. Blueberry gall midge lays eggs inside susceptible,
young green shoot tips. Their larvae hatch and their feeding kills the shoot tip. This shoot
damage causes branching in the infested shoot, resulting in one or more lateral shoots growing
off the primary growth, creating a witches broom effect, which is suspected of reducing plant
growth and bud set. In this study, I examined whether infestation by blueberry gall midge
reduces the number of flower buds set when compared to uninfested shoots. Infested and
uninfested shoots of bushes at blueberry farms were counted and compared to determine whether
there is any effect of the branching caused by the blueberry gall midge damage on fruit bud
production. There was no significant reduction in the number of flower buds set on shoots that
were damaged in the early summer when the majority of new growth is seen, but there were
significantly fewer buds set on shoots damaged later in the summer.

56

INTRODUCTION
Blueberries are an important specialty crop to consumers due to their high nutritional value and
antioxidant content whose production has been increasing worldwide. The United States is the
leading blueberry producer in the world, and Michigan is the leading producer and exporter of
blueberries. The blueberry industry in Michigan has historically needed to manage insect pests
that can cause significant losses in yield. Typically, these insects feed directly on berries, such as
the spotted wing drosophila (Drosophila suzukii Matsumura) that oviposit their eggs inside the
berries, and pose an obvious threat to fruit marketing. Insects that consume foliage, limiting
photosynthesis, or reduce the vigor by feeding on sap such as leafrollers or aphids are indirect
pests that are often overlooked because the effects of their damage are not seen until it becomes
apparent.
Blueberry gall midge (Daineura oxyoccana Johnson) is a potential indirect pest of
blueberries in Michigan whose larvae cause damage to the young shoot tips of growing
vegetative shoots. In Florida, southern Mississippi and southeastern Georgia, this insect has been
shown to damage flower buds and vegetative buds (Steck et al. 2000); this has not been observed
in Michigan blueberries. Losses of up to 90% of flower buds in some southern US blueberry
fields have been attributed to damage by blueberry gall midge (Lyrene and Payne 1992), and
damage to the Florida blueberry industry by this insect has been estimated at $20 million
(Dernisky et al. 2005). In Michigan, gall midge larvae have not been seen in flower buds, but
they have been found inside young vegetative shoots.

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BLUEBERRY SHOOT DEVELOPMENT
To understand the potential impact of blueberry gall midge damage, information about
blueberry bush growth should be reviewed. Blueberry growth and development was reviewed by
Eck (1988) and Gough (1994). Leaf bud break in the early spring is influenced by temperature,
light, internal water balance and hormone levels. Blueberry shoot growth is variable during the
season, with cycles of slow and fast shoot elongation. This cycle repeats until the fall when shoot
growth stops as a result of changes in temperature and photoperiod. Many factors influence an
individual shoot‟s growth patterns, and shoots will elongate at different times. Some shoots will
experience bud break and shoot growth in the fall, resulting in growth that cannot harden and
survive the winter. These shoots are known as proleptic shoots, and are known to have poor
productivity (Gough 1994).
Hardening of shoots begins when growth stops in the fall and continues during the first
frost. Flower buds are able to withstand temperatures as low as -40 ˚C, but fluctuating
temperatures can also detrimentally affect buds. Flower buds can be damaged by ice crystal
formation within the bud as well as damage to the vascular tissue, which restricts nutrients,
water, and hormones from the bud. The location of the flower bud on the stem influences its
ability to survive through winter temperatures. Those at the tips of shoot are not able to harden as
well as those lower on the branch, and are more likely to be killed. There are other factors that
promote hardening, such as low nitrogen content and dry soil. In addition, certain cultivars are
known to be “hardier” than others. For example, blueberry cultivars „Bluecrop‟ and „Elliott‟ are
known to be hardier than cultivars „Coville‟ and „Berkeley‟.

58

BLUEBERRY GALL MIDGE DAMAGE
When blueberry gall midge larvae damage the apical meristem of vegetative blueberry
shoots, lateral shoots are induced to grow, resulting in an effect similar to witches‟ broom
(Tanigoshi et al. 2010). Witches‟ broom is a deformity in woody plants typically caused by a
pathogen in which shoots cluster together, forming a dense mass of twigs that looks like a
broom. True witches‟ broom with a mass of twigs has not been observed; however, up to three
lateral branches have been observed growing from shoots infested by blueberry gall midge. This
outgrowth of extra shoots could potentially cause a decrease in net fruit bud formation if the
plant is spending resources in the additional lateral branching. Additionally, freezing
temperatures may damage shoots, especially buds, if they do not have the time to become winterhardy. Cold injury often results in the loss of the terminal flower buds, and hence reduce yield. A
damaged shoot that has a greater number of younger lateral shoots with more terminal buds than
a single undamaged shoot may be more likely to sustain damage during Michigan‟s cold winter
months.
Conversations with growers indicate little concern regarding blueberry gall midge. None
have mentioned reductions in fruit yield, and some have even suggested that blueberry gall
midge is beneficial because its damage to vegetative shoots promotes extra lateral growth and
perhaps flower bud formation. However, indirect effects may include reduction in fruit bud
formation, flower and fruit set, and increased risk to frost damage. This has not been investigated
in any past studies.
Since evidence of damage by blueberry gall midge on the fruit-bearing parts of the
blueberry bush has not been found in Michigan, it would be useful to know if damage to the
vegetative shoots is indirectly causing a reduction in fruit bud or flower numbers. To determine

59

the effect of blueberry gall midge damage on fruit bud yield, uninfested and infested shoots were
tracked through two fall-to-spring seasons to determine the effect of this potential on highbush
blueberry.

METHODS
Effect of blueberry gall midge on highbush blueberry
In October 2009, the number of developing flower buds was counted on 30 shoots showing
symptoms of blueberry gall midge and 30 uninfested shoots at each of four highbush blueberry
farms. Whenever possible, the uninfested shoots were selected from the same bush where the
infested shoot was selected. Farms were located in Berrien County (1), Van Buren County (2),
and in Grand Traverse County (1), Michigan. Infested and uninfested shoots were selected from
a small section of each field.
The number of flower buds was counted on each of the selected infested and uninfested
shoots as well as on each of the lateral branches of the infested shoots. On the uninfested shoots,
the number of flower buds was counted along the whole length of the shoot (Figure 4.1). After
counting, the shoot was flagged and the number of surviving buds were counted in the spring of
2010.

60

Figure 4.1. Buds on a highbush blueberry shoot that is uninfested (A) and infested (B) by
blueberry gall midge.

In the fall of 2010, three blueberry fields in Van Buren County and one field in Grand
Traverse County were assessed. The bushes assessed were all of cultivar „Bluecrop‟. In the three
blueberry farms in Van Buren County, up to 20 damaged infested shoots were flagged in each of
June, July and August. These 20 shoots were not all flagged at the same time, but rather
throughout each month. All shoots were selected within a field of 100 bushes, and were
confirmed to be infested by blueberry gall midge through inspection of the damaged shoot tips.
Shoots were assessed in Grand Traverse County in November. Since assessment was conducted
after leaf drop, these shoots were not confirmed to be infested by blueberry gall midge during the
summer. Depending on the amount of infestation, some bushes had multiple infested shoots,
whereas others had one. Uninfested shoots were not selected until the bud count in November,
when these shoots showed no sign of lateral branching.
In November, at each farm, the number of flower buds on each infested and uninfested
shoot was counted. On the infested shoots, the number of branches and the number of flower
buds on each of those branches were counted. On the uninfested shoots, the number of flower
61

buds was counted. In March 2011, the number of flower buds was recounted on each shoot, and
the lengths of the shoots were measured. To quantify growth over the winter, each branch of
shoots infested in June, July and August, the length from the point of damage to the apex of each
branch was measured.

Statistical analysis
All data were analyzed using JMP 8.0.2 (SAS, Cary, NC). To determine the effect of blueberry
gall midge infestation on the number of buds per shoot, the number of flower buds on uninfested
shoots and infested shoots was compared using one-way analysis of variance and with means
separation using Tukey‟s HSD test. Data on the number of flower buds on uninfested shoots and
shoots infested in June, July or August did not meet the assumptions of ANOVA and were
compared using a nonparametric Kruskal-Wallis one-way analysis of variance. Shoot lengths
were compared by month of damage using one-way analysis of variance.

RESULTS
In both years, the number of flower buds on uninfested shoots and infested shoots was not
significantly different. In the fall of 2009 (F = 1.69; df = 1,10; P = 0.22) and the fall of 2010 (F =
0.39; df = 1,12; P = 0.55) (Table 4.1) there was no significant difference. In the fall of 2009, the
number of flower buds on uninfested shoots was 4.7 ± 0.4, compared with 5.6 ± 0.6 on infested
shoots. In 2010, the number of flower buds on an uninfested shoot was 5.4 ± 0.8, compared with
4.6 ± 0.8 on infested shoots.
When shoots damaged in 2009 and 2010 were checked in the spring of 2010 and 2011,
respectively, the number of flower buds on uninfested and infested shoots was not significantly

62

different. In the spring of 2010, although there was a lower number of flower buds on uninfested
shoots than on infested shoots, it was not significantly different (F = 4.36, df = 1,10, P = 0.06),
and the trend was not consistent between years. The number of flower buds on uninfested shoots
was 4.0 ± 0.2, compared with 5.3 ± 0.6 on infested shoots (Table 4.1). In the spring of 2011,
there was no significant difference (F = 0.43, df = 1,10, P = 0.53). The number of flower buds on
uninfested shoots was 4.7 ± 1.0, compared with 3.7 ± 0.7 on infested shoots.

Table 4.1. The number of flower buds (± S.E.) in fall of 2009 and 2010 and
spring of 2010 and 2011 on uninfested shoots and shoots infested by
blueberry gall midge.
Number of flower buds
Fall 2009
Fall 2010
Spring 2010
Spring 2011
Uninfested
4.7 ± 0.4
5.4 ± 0.8
4.0 ± 0.2
4.7 ± 1.0
Infested
5.6 ± 0.6
4.6 ± 0.8
5.3 ± 0.6
3.7 ± 0.7

When examined at the individual branch level, as expected the number of flower buds on
infested shoots was significantly lower than on uninfested shoots. In fall of both years, this
difference was statistically significant (F = 9.68, df = 1,12, P < 0.001) (Table 4.2). In fall of
2009, the number of flower buds on uninfested shoots was 4.7 ± 0.4 compared with 2.3 ± 0.2 on
branches of infested shoots. In fall of 2010, the number of flower buds on uninfested shoots was
5.4 ± 0.8 compared with 2.7 ± 0.5 on branches of infested shoots.
When shoots damaged in 2009 were checked in the spring of 2010, the number of flower
buds on uninfested and infested shoots was found to be significantly different. There were
significantly fewer flower buds on branches of infested shoots than on uninfested shoots (F =
40.22, df = 1,10, P < 0.0001). The number of flower buds on uninfested shoots was 4.0 ± 0.2
compared to 2.1 ± 0.2 on branches of infested shoots (Table 4.2). When shoots damaged in 2010
were checked in the spring of 2011, there was no significant difference between the number of

63

flower buds on uninfested shoots and branches of infested shoots (F = 4.4, df = 1,10, P = 0.06),
although the average number of buds was slightly lower on uninfested shoots. The number of
flower buds on uninfested shoots was 4.7 ± 1.0 compared with 2.3 ± 0.6 on branches of infested
shoots (Table 4.2).

Table 4.2. The number of flower buds (± S.E.) in fall of 2009 and 2010 and
spring of 2010 and 2011 on uninfested shoots and branches of shoots
infested by blueberry gall midge.
Number of flower buds
Fall 2009
Fall 2010
Spring 2010
Spring 2011
Uninfested
4.7 ± 0.4
5.4 ± 0.8
4.0 ± 0.2
4.7 ± 1.0
Infested
2.3 ± 0.2
2.8 ± 0.5
2.1 ± 0.2
2.3 ± 0.6

When uninfested shoots and the three different timings of damage were compared, there
was a trend towards lower bud production per shoot on branches damaged later in the season but
no significant difference among treatments in the number of flower buds (H = 3.56, df = 3, P =
0.31) (Figure 4.2). However, the data indicate a reduction in the number of flower buds in shoots
damaged later in the summer. When the spring 2011 bud counts were compared by month of
damage in spring 2011, there was no significant difference (H = 3.31, df = 3, P = 0.35). There
was also no significant difference between the number of flower buds on uninfested shoots and
branches of infested shoots (H = 5.77, df = 3, P = 0.12).

64

8
A

# of fruit buds

7

A

6

A

5
4

A

3
2
1
0
Uninfested

June

July

August

Figure 4.2. Mean (± S.E) number of flower buds (± S.E) in fall of 2010 and 2011 on
uninfested blueberry shoots and shoots infested by blueberry gall midge compared by
month of damage. Bars with the same letter are not significantly different (P < 0.05).

When comparing length of branches of shoots infested in different months, there was no
significant difference in the length of branches of shoots infested in all months (F = 0.19, df =
2,6, P = 0.83). The average length of a shoot infested in June was 16.5 ± 5.1, in July, 13.9 ± 1.9,
and in August, 14.2 ± 1.8.

DISCUSSION
Blueberry gall midge infests vegetative shoots of blueberry bushes in Michigan, and since
infestation of a shoot can induce lateral branching, this could indirectly cause a reduction in fruit
bud and yield in the year following damage. In Washington, lateral branching was mentioned but
the economics of it were not explored (Tanigoshi et al. 2010). The data presented here indicate
that there was no significant difference between the number of flower buds on uninfested shoots
and infested shoots. This suggests that blueberry gall midge injury to highbush blueberry in

65

temperate climates poses a minimal threat to blueberry production. This is encouraging for
growers, some of whom do not mind or even welcome the damage because it stimulates growth.
Since the terminal buds are the most susceptible to frost damage (Gough 1994), there may be a
greater number of flower buds lost on infested shoots than on uninfested shoots during the cold
conditions of the winter. However, my samples collected in the spring indicate no significant
change in the number of flower buds, and no significant difference in the number of flower buds
on uninfested and infested shoots. Further investigations will compare the flower and fruit yield
on uninfested and infested shoots. Thus far, the data are encouraging since there is no evidence
for a reduction in fruit bud set overall, and there does not seem to be greater fruit bud death in
infested shoots as a result of the winter temperatures.
When compared by the month of infestation, the number of flower buds on shoots that
were damaged in June, July and August were not found to be significantly different from the
number of flower buds on uninfested shoots. Additionally, the length of damaged shoots was not
found to be different depending on the month of damage. However, the data suggest a trend
towards a reduction in the number of flower buds in shoots damaged in July and August. These
shoots had the least amount of time to grow and develop flower buds before winter. Although
shoots damaged in August had fewer flower buds, at that time there were low populations of
blueberry gall midge (Chapter 2). These trends in declining bud numbers with time of shoot
growth may also simply reflect a change in the inherent bud production of the blueberry bushes
since there was no internal untreated control for each month. Also, the largest number of
vulnerable green shoots appeared in the beginning of May, over two months before the peaks of
blueberry gall midge infestation in July and August, when there were very few vulnerable shoots
suitable for infestation (Chapter 2). Although late-blooming cultivars such as “Elliott” may have

66

more vulnerable shoots later in the season than earlier varieties such as „Bluecrop‟, the number
of vulnerable shoots may still be comparatively low compared with the abundance in the spring.
Due to its quick generation time and continuous emergence throughout the summer,
blueberry gall midge would be a difficult insect to control. However, since blueberry gall midge
does not directly damage flower buds of blueberries in Michigan and its vegetative shoot damage
does not seem to have an effect on fruit bud yield, the need for control of this insect seems to be
minimal in mature highbush blueberry fields.

67

CHAPTER 5

PHENOLOGY AND CHEMICAL CONTROL OF SCALE
INSECTS IN HIGHBUSH BLUEBERRY

ABSTRACT
Putnam scale and European fruit lecanium scale are occasional pests of blueberries that have
recently been found infesting a small number of blueberry farms in localized regions of
Southwestern Michigan. Although their biology has been studied in other states, scale insects of
the same species are known to vary regionally in their phenologies and voltinism. In Michigan,
the number of generations of both scale insects and the timing of crawler emergence is not
known. This knowledge would be useful for growers targeting crawlers to prevent future
infestation. I investigated crawler emergence and movement of Putnam and European fruit
lecanium scales and found Putnam scale at very low levels in few blueberry farms. In 2010, I
found a peak of lecanium scale crawler movement in late June. To test activity of insecticides
commonly used in conventional blueberry farms, a laboratory bioassay and field trial were
conducted on adult scale insects. The laboratory bioassay indicated activity of acetamiprid,
imidacloprid, spirotetramat, and sulforix on adult scale insects, whereas the field insecticide trial
was inconclusive due to lack of a control sample.

INTRODUCTION
Scale insects are occasional pests of blueberries, Vaccinium corymbosum. Putnam scale,
Diaspidiotus ancylus (Comstock), and terrapin scale, Mesolecanium nigrofasciatum (Pergande),

68

have been cited as the most common scale insects on blueberry stems (Eck 1988). Azalea scale,
Eriococcus azaleae Comstock, was found on blueberries in the Pacific Northwest in 2006, and is
controlled with IPM techniques such as winter pruning and application of dormant oil (Walton
2006). In Michigan blueberries, Putnam scale and European fruit lecanium scale,
Parthenolecanium corni, (Bouché) have been found. Other scale insects are present as economic
pests in Michigan, such as the pine tortoise scale, Toumeyella parvicornis Cockerell, which
infests many species of pine and has been a pest of Michigan Christmas trees (Bishop et al.
1994).
The biology and ecology of Putnam scale has been reviewed by Miller and Davidson
(2005). It is a species of armored scale that is native to North America with a wide range of host
plants in many different plant families and genera. It has either one or two generations per year
depending on its location and host. In both one and two-generation Putnam scale, the insect
overwinters as second-instar crawlers on the bark of the host plant, although adult females have
been found overwintering in Ohio. In New Jersey blueberries, Putnam scale has two generations
per year with peaks of crawler emergence in late May and in early to mid-August (Polavarapu et
al. 2000). High levels of infestation by Putnam scale can kill twigs and branches. In addition, it
occasionally infests and deforms blueberries, which affects berry marketing by causing cosmetic
damage that is unsightly to consumers. Pruning old canes and application of dormant oil can
keep this pest from becoming an economic problem in blueberries (Marucci 1966). Nine species
of parasitoids have been found from canes infested by Putnam scale, and the lady beetle
Microwesia misella (LeConte) was found interacting with the scale (Polavarapu 2000).
The biology and management of European fruit lecanium has been reviewed by Pfeiffer
(1997). It is a soft scale that occurs throughout most of the northern hemisphere, and is mostly a

69

pest of stone fruits in orchards. Lecanium scale typically has one generation per year, but it has
also been found to have two generations in southern Hungary and in southern Pennsylvania.
Egglaying occurs in mid-May and continues through June. Crawlers appear throughout those
months and continue into July. In England, however, egglaying was found to occur at the end of
June with crawlers appearing in August (Wardlow and Ludlam 1975). The most threatening
source of damage by lecanium scale is from the growth of sooty mold on honeydew excreted
from the insect. Dormant oil sprays are an effective chemical control of crawlers (Smith 1961).
Numerous parasitoids have been reported from lecanium scale, all chalcid wasps, and natural
enemies such as lady beetles and lacewings have been documented.
In Michigan blueberries, scale insects have generally been classified as minor pests that
have been controlled through biological control and the use of dormant horticultural oils and
pruning. In recent years, however, scouts and growers have noticed higher numbers of Putnam
and European fruit lecanium scale in localized areas of the blueberry production region in
southwest Michigan. If left unchecked, these populations could reach economic thresholds by
killing bushes and making berries unmarketable. Although the life cycles of Putnam and
lecanium scales are known in other locations, their life cycles and phenologies are unknown in
Michigan blueberries.
Mature scales that have developed their scale covering are difficult to control using
contact insecticides, and many commonly used pesticides such as organophosphates, carbamates
and pyrethroids have long residual activity, which could decrease natural enemy populations.
Horticultural oils were some of the first chemicals used to control scale insects, and act by
suffocating the insects in their first instar. They are typically applied as dormant-season sprays to
avoid suffocation of plant buds and leaves, and have been effective at controlling many types of

70

scale, including European fruit lecanium in peaches (Asquith 1949) and euonymus scale
(Unaspis euonymi) in Japanese pachysandra (Pachysandra terminalis) (Sadof and Sclar 1995).
Timing of application is crucial so that first instar crawlers are targeted. Insect growth regulators,
insecticides that can disrupt the molting process, have been found to be effective on the earliest
instars of scale insects. The insect growth regulator pyriproxifen (Esteem) is labeled for use in
blueberries and targets scale crawlers by mimicking juvenile hormone. This has been found to be
active on California red scale, Aonidiella aurantii, causing mortality of 80% to 100% of first
instar crawlers (Eliahu et al. 2007).
The purpose of this study was to determine the number of generations of Putnam and
lecanium scale on Michigan blueberries and their phenology in this region through monitoring,
and to determine the effects of insecticides on scale survival in a laboratory bioassay and field
trial.

MATERIALS AND METHODS
Monitoring of Putnam scale and lecanium scale crawlers
In 2009, three blueberry farms with known infestations of Putnam scale and lecanium scale were
selected for monitoring. All three of these sites were located in western Michigan. One was
located near Grand Junction, another near West Olive, and the third near Grand Haven. At all
farms, bushes were of the cultivar „Bluecrop.‟ Bushes were spaced 1.22 m apart and rows were
spaced 2.74 m apart. At all three of the farms, five transects containing five bushes each were
flagged. At two of the farms, selected bushes were separated by 10 bushes. At the other farm,
due to availability of space, selected bushes were separated by 3 bushes each. The separation
between these bushes at this farm was smaller because infestation was localized to a smaller

71

portion of a field. At this farm, we also found heavy scale infestation of surrounding trees,
whereas no scale was found in the surrounding trees of the other two farms. At all of the study
sites, monitoring was conducted with the use of double-sided sticky tape (3M, Two Harbors,
MN). First, black electrical tape was wrapped around a randomly selected branch picked within
the canopy of the bush. Double-sided tape was then wrapped around the electrical tape. Two of
these crawler traps were placed on each bush for a total of 50 pieces of tape per site. Each week,
beginning on July 21, 2009 and ending on September 12, 2009, the 150 pieces of tape were
retrieved and replaced with new tape. The number of crawlers on each piece of tape was counted
under a dissecting microscope, and the average abundance per tape and per farm was calculated
for each week.
Due to the low numbers of Putnam scale in 2009, sampling was discontinued for this
insect and only casual observations were made in 2010. In 2010, three blueberry farms with
known infestations of lecanium scale were chosen to be monitored. These farms were located
near Holland and West Olive, MI. At one of the farms, most of the 2.42-hectare field was
infested. There was no infestation of surrounding trees. At the other two farms, only one forested
edge of the blueberry field was infested. At all three sites, 10 infested bushes were randomly
selected to be monitored. Double-sided tape was wrapped around one branch on each bush.
th

th

Every week, beginning on May 27 and ending on August 9 , the 30 pieces of double-sided
tape were retrieved and replaced. The number of crawlers on each piece of tape was counted
under a dissecting microscope, and the average abundance per tape and per farm was calculated
for each week.
After crawler densities on the double-sided tape had declined in August, and as crawlers
moved onto blueberry leaves, 10 leaves were collected per site for a total of 30 leaves. Beginning
72

th

on August 9th and ending on September 27 , the number of crawlers on each leaf was counted
under a dissecting microscope, and the average abundance per leaf and per farm was calculated
for each week.

Fruit sampling for Putnam scale
The farms located near West Olive, MI and Grand Haven, MI that were used for monitoring
were also used for fruit sampling for Putnam scale in 2009. At the farm near West Olive, MI, on
st

August 31 , ripe berries from bushes of the cultivars „Bluecrop‟ and „Elliott‟ were sampled for
thirty minutes. All berries were picked from a portion of the field closest to the forest edge. The
number of berries and the number of scale insects observed on the berries was counted. At the
st

farm near Grand Haven, MI on August 31 , ripe berries from bushes of cultivar „Bluecrop‟ were
sampled. The number of berries and the number of scale insects on the berries was counted.

Insecticidal control of lecanium scale
A laboratory bioassay was conducted to compare the efficacy of insecticides for control of
lecanium scale insects in highbush blueberry. The bioassay was conducted on May 5, 2010. Over
100 shoots infested with live adult lecanium scale were collected at a farm in West Olive, MI,
transported to the laboratory and placed in water picks. Water was replaced in the water picks as
needed. Prior to treatment, the number of live lecanium scale was counted on each shoot. Shoots
were then dipped in one of eight treatments (Table 5.1) for 10 seconds. Solutions were mixed in
a wide mouthed Nalgene bottle to be equivalent to field rates of insecticides in 100 gallons of
water per acre. Treated shoots were allowed to dry in a fume hood and held at room temperature

73

for one week before assessment. At that time the number of live and dead lecanium scale per
shoot was counted, recorded and used to calculate percent mortality for each of 10 replicates.
Percent scale mortality values for each treatment were arcsin transformed and compared among
treatments using analysis of variance (JMP 8.0.2, Cary, NC) and between treatments using
Tukey‟s HSD (JMP 8.0.2, Cary, NC) for means separation.

Table 5.1. Treatments used in the insecticide bioassay of
European fruit lecanium scale.
Treatment
water control
acetamiprid
esfenvalerate
imidacloprid
pyriproxifen
spirotetramat
spirotetramat
calcium polysulfide

Trade name
Assail 30SG
Asana XL
Provado 1.6 F
Esteem 35WP
Movento 2SC
Movento 2SC
Sulforix

Rate (per acre)
5.3 oz
9.6 fl oz
8.0 fl oz
5.0 oz
5.0 fl oz
8.0 fl oz
128.0 fl oz

Field evaluation of an un-replicated field trial was conducted to compare azinphos-methyl
(Guthion), acetamiprid (Assail), and esfenvalerate (Asana) for control of lecanium scale. This
demonstration was performed using a six-acre, lecanium scale-infested field of mature highbush
blueberry, cultivar „Jersey‟, at a farm in West Olive, MI. The field was divided into three areas
and each area received a different insecticide treatment. Three acres received azinphos-methyl
(Guthion WP at 0.5 lb/acre), one and half acres esfenvalerate (Assail at 5.3 oz/acre), and one and
half acres received acetamiprid (Asana at 9.6 oz/acre). Insecticides were applied on June 3 and
17, 2010 by the farm owner using 25 gallons of water per acre. The middle three rows of each
treated section of the field were assessed before insecticide application, seven days after
treatment (DAT) and 14 DAT. Assessments were conducted to record the number of live and
74

dead lecanium scale on 20 infested canes in each treated area. Since there was no control
treatment, no statistical analysis was conducted.

RESULTS
Monitoring of Putnam scale and lecanium scale crawlers
In 2009, Putnam scale crawlers were caught from July 21 until September 12. The number of
crawlers caught per tape was highest at the beginning of trapping with an average of 15 ± 2
crawlers per tape (Figure 5.1). There was another small increase in crawler numbers in early
September.
In 2010, European fruit lecanium scale early instar crawlers were caught within a fiveweek period, between June 10 and July 20 (Figure 5.2). The largest catch of crawlers was on
June 28, with an average of 216 ± 45 crawlers caught per tape. There were 1084 accumulated
growing-degree days, base 50 ˚F, from March 1 at this date. Inspection of blueberry leaves
showed high levels of crawler infestation from the beginning of August through the end
September, with an average of over 20 crawlers per leaf at all sampling dates except for
September 11, which had an average of 8 ± 2 crawlers per leaf (Figure 5.3).

75

Avg # of crawlers per tape

20
18
16
14

12
10
8
6
4
2
0
7/21

7/28

8/4

8/11

8/18

8/25

9/1

9/8

Figure 5.1. Phenology (crawlers per tape ± S.E.) of Putnam scale and European fruit
lecanium scale crawlers on Michigan blueberry in 2009. Species could not be separated at
the crawler stage.

Average # of crawlers per

300
250
200
150
100
50
0
6/2 6/9 6/16 6/23 6/30 7/7 7/14 7/21 7/28 8/4
Figure 5.2. Phenology (crawlers per tape ± S.E.) of European fruit lecanium scale crawlers
on Michigan blueberry in 2010.
76

35

Avg # of scale per

30
25
20
15

10
5
0
8/9

8/16

8/23

8/30

9/6

9/13

9/20

9/27

Figure 5.3. Phenology (crawlers per tape ± S.E.) of European fruit lecanium scale on
blueberry leaves in 2010.

Fruit sampling for Putnam scale
At the farm near West Olive, MI, 54 Putnam scale were found on 592 sampled Bluecrop‟ berries
(9.1% infested with Putnam scale). On „Elliott‟ berries there were 22 Putnam scale found on 373
sampled berries (5.9% infested with Putnam scale). Only one scale per berry was found in these
samples. Over 1000 berries were collected from the farm in Grand Haven, MI, but no scale
insects were found on them.

Insecticidal control of lecanium scale
In the bioassay, the control and pyriproxifen treatments had the lowest scale mortality. The other
treatments had significantly higher mortality. There was significant mortality compared to the
77

control in all treatments except for pyriproxifen (F = 8.3, df = 7,32, P < 0.0001), with the highest
levels of control provided by imidacloprid and sulforix (Table 5.2).
Table 5.2. Control of European fruit lecanium scale
in laboratory bioassay. Mortality values followed by
the same letter are not significantly different.
Average mortality
(± S.E) was compared using
analysis of variance.
Treatment

% mortality

water/control
acetamiprid
esfenvalerate
imidacloprid
pyriproxifen
spirotetramat (5 oz)
spirotetramat (8 oz)
sulforix

18.2 ± 6.9
76.2 ± 12.2
56.7 ± 20.8
100.0 ± 0.0
13.0 ± 8.3
94.4 ± 5.6
66.7 ± 33.3
100.0 ± 0.0

B
A
AB
A
B
A
AB
A

In the precount before the field insecticide trial, the shoots had low scale mortality (Table
5.3). The mortality of scale increased to 20% seven days after treatment and to about 65%
fourteen days after treatment, with similar levels of mortality among the three treatments.

Table 5.3. Field insecticide trial for control of European fruit lecanium scale. Values are %
scale mortality (± S.E) per shoot. There was no control treatment.
Treatment
acetamiprid
Precount
7 DAT
14 DAT

azinphos-methyl

1.7 ± 0.9
22.7 ± 3.9
71.1 ± 4.1

1.3 ± 0.6
17.5 ± 3.1
67.0 ± 5.0

78

esfenvalerate
1.35 ± 0.65
25.1 ± 4.1
61.6 ± 4.3

DISCUSSION
Putnam scale has been known to be an occasional pest on blueberries. Infestation can cause shoot
dieback, reduce plant vigor (Antonelli et al. 1992) and cause deformities on the berries
(Polavarapu et al. 2000). Lecanium scale is mostly a pest of stone fruit orchards, but can also
utilize blueberries (Polavarapu et al. 2000) and non-fruit trees as hosts (Pfeiffer 1997). Scale
insects have had a limited effect on the Michigan blueberry industry and have not shown a large
economic impact on blueberry production and yield. In recent years in Michigan farms, there
have been increased reports of blueberry bushes infested with Putnam scale and lecanium scale.
Although Putnam scale and lecanium scale were present in 2009, they did not reach high
enough levels to cause significant damage to the fruit or to the bushes. No distinct peak of
crawler movement was found that year because trapping was started so late in the season. In
New Jersey, Putnam scale has two generations per year (Polavarapu et al. 2000), and crawler
emergence occurs in late May and again in early to mid-August. In addition to the late start with
trapping, it was not known which crawlers were Putnam scale and which were lecanium scale, so
it is difficult to determine the number of generations per year of either scale. There may have
been overlapping emergence of Putnam scale and lecanium scale crawlers, causing a longer flush
of crawlers to be caught. The fruit sampling for Putnam scale was done to show that the numbers
of scale found on berries was not at high enough populations to significantly damage fruit. Those
berries that did have Putnam scale had only an individual scale on them that was easily washed
off.
In 2010, with the focus on blueberry fields infested with lecanium scale, monitoring
indicated a distinct peak of crawler emergence at the end of June. Typically, there is one
generation of crawlers that emerges between mid-May and early June in Virginia (Pfeiffer 1997),

79

although other active crawler periods have been found. Two generations of lecanium scale have
been found in southern Hungary (Kosztarab 1959) and in southern Pennsylvania (Asquith 1949).
In the monitored farms in Michigan, only one generation of lecanium scale was evident. The
crawlers that had moved onto the blueberry leaves were second-instar nymphs that were
preparing to overwinter.
Two of the farms had heavy infestation only near the forested edge, where there were
alternate hosts for the lecanium scale, including maples, sassafras, wild blueberry and oaks.
Some of these trees were so highly infested that it was impossible to see the bark underneath the
numerous insects. It is reasonable to say that those bushes near the forested edge were infested
by crawlers that had drifted down from the trees. The other farm had heavy infestation
throughout the entire field, where there were no surrounding infested trees. Most likely, the
infestation had been present in the field for multiple seasons and had been allowed to increase.
The insecticide bioassay indicated that there was significant control of adult lecanium
scale by all compounds tested except for pyriproxifen, Esteem, which is labeled for control of
lecanium scale insects in blueberries. Although pyriproxifen did not lead to higher mortality of
lecanium scale, as an insect growth regulator, it is a product that is meant to be used on the
crawler stage of scale insects, so the timing was not appropriate in this study. The label also
recommends that it be used with a delayed dormant oil, which has been shown to be effective at
controlling lecanium scale (Asquith 1949). The bioassay was conducted on May 5, 2010, which
was seven weeks before the peak crawler emergence we determined from monitoring. I was
unable to draw any conclusions from the field insecticide trial due to the lack of any control.
Although there was a reduction in the number of live adult scales, it is unknown if that is
attributed to natural death or to the insecticide application. In future studies, insecticide trials

80

should take crawler emergence into account so that applications are made to coincide with
crawler activity.
Having only been found in a small region of Michigan, scale insects have not had a
noticeable impact on Michigan blueberries, most likely due to pruning practices, pesticide
application for other insects, and natural enemy populations that maintain the populations at low
levels. However, given the opportunity, with changing pesticide regulations and changes in the
environment, scale could become a more significant pest in this region. In preparation, it is
useful to have guidelines on when to monitor for and manage scale if it becomes a problem.

81

Chapter 6

CONCLUSIONS AND FUTURE RESEARCH

The blueberry industry in Michigan has historically been the target of insect pests. With
the implementation of integrated pest management techniques, growers have become more aware
of the need to understand the biology of pests in order to more effectively manage them. With
the reduced use of broad-spectrum insecticides and the switch to specialized reduced-risk spray
programs, this need for knowledge has become even more important. Secondary pests that have
previously been controlled with the broad-spectrum insecticides may have had an opportunity to
increase in population. For example, blueberry gall midge and scale insects are two such
secondary pests that have been sighted in Michigan blueberry fields with greater frequency in
recent years, but it is not known if they pose a threat to the industry.
Prior to this study, the distribution and biology of blueberry gall midge in Michigan
blueberries was unknown. Our survey revealed that blueberry gall midge is present throughout
the state‟s blueberry fields, from Berrien County north to Grand Traverse County and east to
Genesee County. With this distribution, their potential to be economically destructive is easily
seen. This study investigated the biology of blueberry gall midge through multiple monitoring
techniques, tested insecticide treatments and documented natural enemies. Although some
phenological research has been done in Florida and the Pacific Northwest, their climates and
Vaccinium species grown are different from those in Michigan. The data from this study show
the time of the year when blueberry gall midge is most active, and when infestation is highest.

82

With the approaching phaseout of azinphosmethyl, there may be a need to find alternative
pesticides that can also be effective on blueberry gall midge. Pesticides tested in other studies do
not include many insecticides commonly used in Michigan. Our data show that although many
insecticides are able to kill blueberry gall midge, their effectiveness in the field is unreliable.
Although blueberry gall midge parasitoids were present in Michigan, their numbers were found
to be low. If blueberry gall midge is found to be economically damaging, it would be wise to
make efforts to conserve natural enemy and parasitoid populations to avoid the need for
application of chemical insecticides.
Since blueberry gall midge does not attack the flower buds and targets the vegetative
shoots in Michigan blueberries, have a much lower risk of impacting fruit yield. It is unknown
why they do not affect highbush blueberry flower buds, but it could be due to the different
Vaccinium species being cultivated in Florida, rabbiteye blueberry (Vaccinium ashei Reade). A
comparison between species has not yet been conducted. My investigation of any indirect costs
of vegetative shoot damage has thus far shown no significant difference in fruit bud yield in
infested and uninfested shoots. Future studies will look at the resulting flower and fruit yield of
infested shoots, and the effects of cold injury on infested and uninfested shoots.
Putnam scale and European fruit lecanium scale were documented in Michigan
blueberries. One year prior to the beginning of this research, in 2008, Putnam scale seemed to be
increasing to threshold populations to the point of infesting and deforming fruit in a select few
fields. The year this study began, in 2009 the previous population of Putnam scale that had been
deforming fruit was found infrequently on berries, and it was deemed an occasional pest. This
emphasizes the rapid change in pest populations from year to year in this system. One grower
that had some problems with scale insects had sprayed dormant oil and took care to prune off

83

infested canes and reported no problems the following year, so there are relatively effective and
low risk options available for scale management.
European lecanium scale was found in 2009, although in low numbers and localized to a
small region of southwest Michigan. My study investigating its phenology found one peak of
crawlers in late-June; this can be a useful aid for growers to know when to apply mid-season
insecticide sprays. Our insecticide trial indicated control of adult scale with acetamiprid,
imidacloprid, spirotetramat, and sulforix. Future studies should look at the effects of post-harvest
sprays on crawlers beginning to overwinter.

84

APPENDIX

Record of Deposition of Voucher Specimens*

The specimens listed on the following sheet(s) have been deposited in the named museum(s) as
samples of those species or other taxa, which were used in this research. Voucher recognition
labels bearing the Voucher No. have been attached or included in fluid-preserved specimens.
Voucher No.: 2011-05

Title of thesis or dissertation (or other research projects):
Biology and Management of Blueberry Gall Midge and Scale Insects in Michigan Blueberries

Museum(s) where deposited and abbreviations for table on following sheets:
Entomology Museum, Michigan State University (MSU)
Other Museums:
Investigator‟s Name(s)

(typed)

Noel Hahn
Date 8/19/2011
*Reference: Yoshimoto, C. M. 1978. Voucher Specimens for Entomology in North America.
Bull. Entomol. Soc. Amer. 24: 141-42.
Deposit as follows:
Original: Include as Appendix 1 in ribbon copy of thesis or dissertation.
Copies: Include as Appendix 1 in copies of thesis or dissertation.
Museum(s) files.
Research project files.
This form is available from and the Voucher No. is assigned by the Curator, Michigan State
University Entomology Museum.

85

Table A.1.

Number of:

10

10

20

Date

(typed)

8/19/2011

Voucher
No.
2011-05
Received the above listed specimens for
deposit in the Michigan State University
Entomology Museum.
Gary Parsons
8/19/2011
Curator
Date
86

10

10

Museum
where
deposited
Other

10

(Use additional sheets if necessary)
Investigator's Name(s)
Noel Hahn

Adults ♂

Dasineura oxycoccana

Adults ♀

Diaspidiotus ancylus

Pupae

Parthenolecanium corni

Nymphs

West Olive, MI in Ottawa County
Quincy St. and Butternut Dr.
Blueberry farm
8/3/2010
West Olive, MI in Ottawa County
Quincy St. and Butternut Dr.
11/15/2010
Blueberry farm
Benton Harbor, MI in Berrien County
Napier Ave. and Hillandale Rd.
Blueberry farm
8/11/2009
Covert, MI in Van Buren County
72nd St. and 44th Ave.
Blueberry farm
6/1/2010
7/1/2010

Larvae

Parthenolecanium corni

Eggs

Label data for specimens collected or used and
deposited

Species or other taxon

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87

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