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THESIS

 

”1°” LfBRARY
Michigan State
University

 

 

 

This is to certify that the

thesis entitled

INTEGRATED MANAGEMENT STRATEGIES FOR CONTROL OF
CHERRY FRUIT FLIES, RHAGOLETIS CINGULATA AND
RHAGOLETIS FAUSTA (DIPTERA: TEPHRITIDAE)

 

 

presented by

Jessica Lynn Kostarides

has been accepted towards fulfillment
of the requirements for

M.S. Entomology

 

degree in

 

Major professor

Date 8 May, 2002

 

0-7639 MS U is an Affirmative Action/Equal Opportunity Institution

 

PLACE IN RETURN BOX to remove this checkout from your record.
To AVOID FINES return on or before date due.
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6/01 c:/CIRCJDatoDue.p65—p. 1 5

INTEGRATED MANAGEMENT STRATEGIES FOR CONTROL OF CHERRY
FRUIT FLIES, RHA GOLETIS CINGULA TA AND RHA GOLETIS FA USTA
(DIPTERA: TEPHRITIDAE)

By

Jessica Lynn Kostarides

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

Department of Entomology

2002

ABSTRACT
INTEGRATED MANAGEMENT STRATEGIES FOR CONTROL OF
CHERRY FRUIT FLIES, RHA GOLETIS CINGULA TA AND RHA GOLETIS FA USTA
(DIPTERA: TEPHRITIDAE)
By

Jessica Lynn Kostarides

The genus Rhagoletis, of the dipteran family Tephritidae, includes some 50
described species and is widely distributed over the Holarctic and Neotropical regions.
Many of these species are major economic pests of fruit such as cherries. The eastern,
Rhagoletis cingulata (Loew) and black, R. fausta (Osten Saken) cherry fruit flies are
native to North America. They are major pests of cultivated sweet (Prunus avium) and
tart (P. cerasus) cherries. In order to ensure maggot-free fruit to meet the stringent zero
tolerance levels mandated by Federal and State regulations (F RL-6813-9), growers
generally apply two to three applications of broad-spectrum insecticides, primarily
organophosphates, for reduction of fly populations. Implementation of the Food Quality
Protection Act (F QPA) of 1996 may prevent the future use of organophosphates as well
as other conventional insecticides for management of key Rhagoletis species. As a result,
the focus of my research was to investigate the potential of developing an integrated
system for control of cherry fruit flies. This includes: 1) improving current cherry fruit
fly monitoring techniques with RebellTMI traps; 2) identifying reduced-risk compounds that
can be used in cherry fruit fly management programs; 3) deployment of biodegradable
pesticide—treated trapping devices and entomopathogenic nematodes to suppress adult and
larval populations respectively. This project has yielded a new set of pest management

tools for optimizing control of cherry fruit flies.

Copyrighted by
JESSICA LYNN KOSTARIDES
2002

ACKNOWEDGEMENTS

I would like to express my deepest gratitude to my parents, Anestis and Patricia,
and my siblings, Michael and Stacey Kostarides for providing me with their
unconditional love and support that has given me the drive and determination to get me
when I am today. It is with their guidance and inspiration that has allowed me to thrive
and truly enjoy my graduate experience.

I also thank my committee members, Drs. George Bird, John Wise, and
Annemiek Schilder for their valuable assistance in regards to direction and advice during
crucial steps of this project. Furthermore, I would like to thank the entire Department of
Entomology at Michigan State for their enthusiastic support throughout my graduate
education.

Finally I thank my field assistants, and the staff at the Northwest Horticultural
Research Station in Traverse City, MI. It is with their help that made this research
possible. This research was supported by grants from Michigan Agricultural Experiment

Station and GREEEN Grant and USDA Special Grant.

iv

TABLE OF CONTENTS

LIST OF TABLES ................................................................................. viii
LIST OF FIGURES ................................................................................. ix
SECTION I (INTRODUCTION) .................................................................. 1
Michigan cherry industry ................................................................... 1
Biogeographic distribution .................................................................. 1
Courtship behavior and life cycle .......................................................... 3
Nematode classification and biology ...................................................... 5
Michigan monitoring and management programs ....................................... 7
Insecticide history ............................................................................ 8
History of pesticide regulation ............................................................ 11
Research Objectives ........................................................................ 14
SECTION II (RESEARCH) ....................................................................... 16

CHAPTER ONE: VISUAL AND OLFACTORY STIMULII AFFECTING THE

RESPONSE OF CHERRY FRUIT FLIES (DIPTERA:

TEPHRITIDAE).
Introduction ............................................................................................. 17
Materials and Methods .............................................................................. 20
RebellTM Experiment ....................................................................... 20
Fruit versus Foliage ........................................................................ 21
Sampling .................................................................................... 21
Statistical Analysis ......................................................................... 22

Results ................................................................................................. 23

RebellTM Experiment ........................................................................ 23
Fruit versus Foliage ........................................................................ 24
Discussion ............................................................................................ 25

CHAPTER TWO: EVALUATION OF REDUCED-RISK INSECTICIDES AS
ALTERNATEVES TO ORGANOPHOSPHATE INSECTICIDES

FOR CONTROL OF CHERRY FRUIT FLIES (DIPTERA:

TEPHRITIDAE).
Introduction ............................................................................................. 38
Materials and Methods .............................................................................. 43
Insecticide Trials ........................................................................... 43
Monitoring .................................................................................. 44
Laboratory Bioassays ...................................................................... 44
Fly Preparation .............................................................................. 45
Single Dose Assay ......................................................................... 45
Statistical Analysis .......................................................................... 46
Results ................................................................................................. 47
Insecticide Trials ........................................................................... 47
Laboratory Bioassays ...................................................................... 47
Discussion ............................................................................................ 49

vi

CHAPTER THREE: EVALUATION OF AN INTEGRATED SYSTEM FOR

CONTROL OF CHERRY FRUIT FLIES:

BIODEGRADABLE TRAPPING DEVICES AND

ENTOMOPATHOGENIC NEMATODES

Introduction ............................................................................................. 56
Materials and Methods .............................................................................. 62
Biodegradable Pesticide-Treated Sphere Experiment. 2000 .......................... 62
Modified Pesticide-Treated RebellTM Experiment. 2001 .............................. 63
Monitoring .................................................................................. 64
Statistical Analysis ......................................................................... 64
Entomopathogenic Nematode Bioassays. 2000 ......................................... 64
Statistical Analysis ......................................................................... 66
Pesticide Residual Analysis ............................................................... 66
Statistical Analysis ......................................................................... 66
Results ................................................................................................. 67
Biodegradable Pesticide-Treated Trapping Devices .................................. 67
Entomopathogenic Nematode Bioassays. 2000 ......................................... 67
Discussion ............................................................................................ 69
SECTION III (SUMMARY AND CONCLUSIONS) .......................................... 74
APPENDIX ........................................................................................... 76
LITERATURE CITED ............................................................................. 79

vii

LIST OF TABLES

Table 1. Comparison of total male and female Rhagoletis cingulata captures on four
types of traps, Traverse City, MI (2000) .......................................................... 29

Table 2. Comparison of total male and female Rhagoletz‘sfausta captures on four types
of traps, Paw Paw, MI (2001) ..................................................................... 30

Table 3. Percent mortality of Rhagoletis cingulata pupae after exposure as larvae to
106/m2 concentration of infective juveniles of five species of entomopathogenic
nematodes ........................................................................................... 71

viii

LIST OF FIGURES

Fig. 1. Completely randomized block design for modified RebellTM experiment;
treatments rotated within block on a weekly basis ............................................. 31

Fig. 2. Total Rhagoletis cingulata captures 1 July — 25 Aug. on four types of modified
RebellTM traps, Traverse City, Michigan (2000) ................................................. 32

Fig. 3. Comparative population dynamics of Rhagoletis cingulata among four trapping
systems in a Traverse City, MI cherry orchard in 2000 ........................................ 33

Fig. 4. Total captures of Rhagoletisfausta 24 May — 4 July on four types of modified
Rebellm traps, Paw Paw, MI (2001) ............................................................. 34

Fig. 5. Comparative population dynamics of Rhagoletisfausta as measured by four
. trapping systems in a cherry orchard, Paw Paw, MI 2001. .................................... 35

Fig. 6. Attraction of Rhagoletisfausta to RebellTM traps in cherry trees, Prunus cerasus,
Paw Paw, MI (2001) ................................................................................ 36

Fig. 7. Population dynamics of Rhagoletis cingulata caught on baited Rebellm traps in an
abandoned cherry orchard in Leelanau County, MI (2000) .................................... 51

Fig. 8. Influence of six insecticides on Rhagoletis cingulata infestation of cherry fruit as
measured on 18 July 2000 in a cherry research plot in Leelanau County, MI .............. 52

Fig. 9. Influence of six insecticides on Rhagoletis cingulata infestation of cherry fruit as
measured on 28 July 2000 in a cherry research plot in Leelanau County, MI .............. 53

Fig. 10. Percent fly mortality (Rhagoletisfausta) exposed to different insecticides in
bioassay chambers, Michigan State University, MI 2001 ...................................... 54

Fig. 11. Captures of Rhagoletis cingulata from 11-30 July captured on plexiglas panels
beneath biodegradable pesticide-treated (2% a.i. imidacloprid) spheres, Leelanau County,
Michigan (2000) ...................................................................................... 72

ix

Fig. 12. Captures of Rhagoletis cingulata from 1 July — 25 Aug. on plexiglas panels
beneath biodegradable trapping devices, Leelanau County, Michigan (2001).... . . . . . ..73

INTRODUCTION

Michigan Cherry Industry. Michigan is responsible for a significant portion of

 

national and worldwide cherry production. Michigan currently dominates the tart cherry
(Prunus avium L.) industry, generating approximately 75 percent of the crop, along with

12 percent of sweet cherries, P. cerasus L. In 1999, the gross receipts for both tart and
sweet cherries exceeded $50 million (Michigan Agricultural Statistics 1999).

There are nearly 40,000 acres of tart cherries in the state with a total of about 55,000
acres in the United States. There are 3.8 million tart cherry trees grown by about 1,000
growers in Michigan. Nationally, there are 5.5 million tart cherry trees and
approximately 1,500 cherry growers.

The eastern cherry fruit fly, Rhagoletis cingulata (Loew) and the black cherry
fruit fly, R. fausta (Osten Sacken), are important native pests of Michigan cherries. Both
Federal regulations (USDA) and consumers mandate a zero tolerance for maggots in
fruit. Rejection of the entire crop from a block of fruit is a standard practice if a single
larva is detected in the fruit. Therefore, the economic risks to growers encompass direct
loss of yield, loss of export markets, increased control costs, and the expense of
constructing and maintaining fruit treatment and eradication facilities. Cherry fi'uit flies
are the most economically important late-season pests of commercially grown cherries in

the eastern and midwestem United States (F rick et al., 1954).

Biogeographic Distribution. The genus Rhagoletis includes about 50 described

 

species and is widely distributed over the Holartic and Neotropical regions (Bush 1966).

The time and place of the origin of the genus Rhagoletis is not known. The fact that most

of the species within this genus are adapted to high altitudes or temperate climates
supports the theory that the Holartic region is the most probable original center of
radiation (Bush 1966). Furthermore, evidence from floristic history of the Holartic
region indicates that these species arose sometime within the Oligocene or early
Miocene. It is also possible that some of the present sibling species were established
during the Pliocene (Bush 1966). This period most likely marks the time when the
originally proliferate Rhagoletis was broken into three major clades. These clades
include one in Asia, another in eastern North America, and a third in Central and South
America (Bush 1966). The present distribution of this genus supports this hypothesis.

Two native hosts (Prunus pennsylvanica L. and P. serotina Ehrh.) of cherry fi'uit
flies generally harbor maggots at severe infestation rates. Both of these wild cherries are
widely distributed throughout Michigan’s landscape. Cherry fruit flies are well adjusted
to these hosts, as is indicated by the heavy infestations of maggots during peak fi'uiting
season.

While both P. pennsylvanica and P. serotina serve as important native host plants
for cherry fruit flies, the host preferences displayed by these insects is unique. Both
species of Rhagoletis attack the two introduced cultivated cherries (P. avium and P.
cerasus) equally, but their relationship to native wild cherries is more complex.
Rhagoletisfausta is confined to P. pennsylvanica, while R. cingulata prefers P. serotina.
Rhagoletis fausta, the species that regularly appears first in cultivated cherry orchards, is
associated with the early maturing P. pennsylvanica in nature; whereas, R. cingulata

prefers the later maturing P. serotina.

Courtship Behavior and Life Cycle. Cherry fruit flies exhibit a wide array of

 

behaviors throughout their adult life stage. These include dispersal, feeding, and
oviposition behaviors, especially in courtship and mating. Males secrete sex-attractant
chemicals, either by inflating the lateral abdominal membranes or by extruding an anal
pouch, to attract female flies. Wing fanning disperses pheromones, which also precedes
sounds of possible significance in courtship. Once on an appropriate host fruit (mating
site) males defend their territory with various aggressive displays including head-on
collision, “boxing” (fight involving prothoracic legs) and wing jerking, while waiting for
females (AliNiazee 1974, Messina and Subler 1995). The female usually visits several
fi'uit prior to oviposition. It spends about 10 days feeding in the vicinity of host fruit and
foliage before laying eggs. Oviposition behavior appears to be more uniform than
epigamic behavior and consists of the following stages: a) movement towards and arrival
at the oviposition site; b) testing the site (for previous oviposition); c) inserting the
needle-shaped ovipositor into the fruit; (1) and depositing a single egg just below the
surface of the fruit. Immediately following egg deposition, the female walks around the
fi'uit dragging her extended ovipositor on the fi'uit surface, marking it with her pheromone
to deter other females from ovipositing in the same fruit, thus preventing competition
with the single larva (Prokopy 1976). Each female is capable of depositing 300 to 400
eggs during the three to four weeks she is active. The eggs hatch in about seven days.
Legless larvae start to feed and tunnel around to the pit of the fruit in approximately two
weeks. There are three to four larval instars, lasting a total of 10 — 21 days. The last
instar emerges from the fruit, falls to the orchard floor, and burrows to a depth of 2-5

inches beneath the soil surface.

The majority of temperate Rhagoletis spp. are univoltine (Fletcher 1989).
Puparial diapause is followed by emergence of adults from the soil beneath host plants
that fruited the previous year. Factors that influence emergence of adults include soil
moisture, temperature, location, and soil type. Emergence coincides closely with the
appearance of host fruit suitable for adult egg deposition. Peak emergence in
southwestern Michigan occurs in early to mid June for the black cherry fruit fly and early
to mid July in northwestern Michigan for the eastern cherry fruit fly (Liburd et al., 2001).

The major natural enemies of a sibling Rhagoletis species, R. mendax Curran, are
two braconid wasp parasitoids, Opium ferruginues Gahan and 0. melleus Gahan. They
emerge from the pupal cases about 25 to 30 days after adult fly emergence (Drummond
and Collins 1997b). The parasitoids locate maggots, and overwinter in the blueberry
maggot puparium.

Predation is also a key factor in regulation of Rhagoletis. spp. populations (Boller
and Prokopy 1976). Ants, staphylinid beetles, carabids, cecidomyiids, and crickets prey
on fruit fly species within the family Tephritidae. Fungi, bacteria, and viruses infect
various tephritid species. To date, however, none have been isolated from natural
populations of cherry fruit fly (Sivinski 1996). This indicates, therefore, a necessity to

investigate alternative biological control methods for suppression of Rhagoletis spp.

Nematode Classification and Biology. Nematode parasites of insects have been
known since the 17th century (Nickle 1984), but it was only in the 19303 that serious
consideration was given to using a nematode to control insects. Nematodes are
vermiform, non-metametrically segmented invertebrates with bilateral symmetry. They
have a digestive system with a three-angled esophageal lumen. Nematodes have separate
sexes. Males have spicules and tubular gonands joining the digestive system to form a
cloaca, and females with both a gonopore and a posterior opening to the digestive system.
Numerically, they are the most abundant multicellular organisms on the planet (Bird
2002, personal communication). Some species function as bacterivores, whereas others
feed as fungivores, algavores, herbivores or omnivores.

Species in the families Steinemematidae and Heterorhabditidae (Rhabditida:
Nematoda) parasitize insects. These are the most economically important
entomopathogenic nematodes. As beneficial organisms they are lethal to many important
soil insect pests and yet are safe for non-target arthropods.

Infective juveniles of Steinemema spp. are 0.5 mm to 1.5 mm in length depending
on the species. They have stoma] and anus plugs and cannot feed until a host is available.
Usually the infective juveniles found in soil, are activated by insect movement and then
follow a gradient of carbon dioxide to find the insect (Gaugler and Kaya 1990).
Entomopathogenic nematodes enter through natural body openings, the mouth, anus or
respiratory inlets (spiracles) and then penetrate into the blood cavity from the gut or
breeding tubes (Poinar 1990). Heterorhabditis spp. can also penetrate through the
insect's interskeletal membranes by scratching away at these with a stomatal tooth

(Bedding and Molyneux 1982).

Once in the insect's blood, infective juveniles release a highly specialized
symbiotic bacterium found only in entomopathogenic nematodes. These are
Xenorhabdus spp. in Steinernema spp., and Photorhabdus spp. in Heterorhabditis spp.
Bacteria multiply, produce toxins, and kill the insect within approximately one day. As
decomposers, bacteria degrade the insect, and replicate, forming food for the nematode.
They also produce a range of antibiotics (Akhurst 1982) and anti-feedants that preserve
the dead insect while the nematodes feed and breed within it.

Because entomopathogenic nematodes require continual oxygenation, it is
impractical to supply them as biological control agents in a water suspension that would
have to be kept continually aerated and would even then only last for a few days.
Temporary refrigerated storage can be achieved by adding a cream of nematodes to
crumbed foam in plastic bags (Bedding 1984) but the consumer has to extract these from
the foam. Further research, however, has led to more suitable means of formulating
entomopathogenic nematodes (Bedding 1986, Bedding and Butler 1994, Wang and
Bedding 1998). The latest formulation is comprised of about 50% micro-cellulose and
50% nematodes that can be readily mixed in spray tanks, sprayed without blocking
nozzles and can survive several months at room temperature. This long shelf life has
been achieved by manipulating the nematodes' physiology. Water is removed from
between the nematodes over a filter under vacuum and then more water (about 50 %) is
removed from within the nematodes by mixing them with just the right amount of dry
absorbent. This causes the nematodes to increase their carbohydrate reserve about 10 %
prior to entering into hibernation. While in hibernation, they may use only one hundredth

of the oxygen that non-hibernating nematodes do and in theory at least can last 100 times

as long. One problem with this is fungal contamination. It has been very difficult to find
a suitable preservative that does not harm the nematodes while providing fungal
degradation at bay for several months. Another problem is that the nematodes must be
kept at precise water content for maximum shelf life. It is also difficult to provide them

with oxygen while preventing water loss.

Michigan Monitoring and Management Programs. For the past three decades,
fi'uit fly management programs in Michigan have primarily relied on the use of visual and
olfactory traps to accurately time insecticide applications. Strategies adapted by most
commercial growers involve hanging baited Pherocon AM yellow sticky boards (Great
Lakes IPM, Vestaburg, MI) in orchards. Afler detection of a single fly, ground or aerial
applications of insecticides are made (Liburd et al. 2001). A major problem with these
traps is that afier two weeks of deployment, the sticky boards become inundated with a
wide variety of non-target insects, reducing their effectiveness (Liburd et al., 1999). In
addition, the odor of the decomposing insects within the Tangle—Trap® interferes with the
insect attractant (ammonium compounds) used with these traps, thus reducing their
effectiveness. These circumstances dictate that traps be cleaned and replaced on
relatively short intervals. Trap preparation, replacement, and maintenance are a time-
consuming and labor—intensive operation (Prokopy et al., 1990). Substantial
improvements in trapping techniques are needed if traps are to be used in the future for
effective monitoring and control programs in commercial cherry production.

Federal laws mandate a zero tolerance for maggot—infested fruit in cherries at

harvest. In order to meet these stringent tolerance standards, fruit fly management

programs in Michigan have relied heavily on prophylactic sprays of broad-spectrum
organophosphate (OP) compounds. Registered insecticides for fruit fly control include
malathion, carbaryl, phosmet, pyrethrin, and azinphos-methyl. Currently, commercial
growers apply two to four scheduled sprays of organophosphate insecticides against the
cherry fruit flies, irrespective of the presence of adults (Liburd et al., 1998).
Organophosphate insecticides are generally effective. They can, however, negatively
affect beneficial insects and other non-target organisms, particularly invertebrates in the
immediate and surrounding habitats. The results can have a significant negative impact
on the full potential of biological control. The future use of organophosphates for
management of fruit flies is likely to be restricted because of the 1996 Food Quality
Protection Act (F QPA). This law requires the Environmental Protection Agency (EPA)

to re—evaluate health risks from pesticides in the US.

Insecticide Histog. The development of concepts for control of fruit-feeding
Rhagoletz's spp. reflects the history of insect control in general. Prior to the 1940’s, the
insecticidal value of a number of inorganic chemicals (i.e. arsenic) and organic chemicals
of botanical origin (i.e. pyrethrum and nicotine) was known, and they were extensively
used.

One of the first synthetic organic insecticides was DDT, a halogenated
hydrocarbon. In 1877, Zeider synthesized DDT. This chemical, however, was not
developed as an insecticide until it was rediscovered by Mtiller in 1936. Dr. Paul Muller
of the Geigy Company of Switzerland developed DDT in 1939. Organochlorine

molecules tend to be relatively stable because of the placement of the chlorine ions in the

molecule. Most of these chemicals have been banned because of their persistence in the
environment and toxicity to non-target organisms. Soon afier DDT was released into the
market in the early 1940’s, primarily to control lice and fleas that were vectoring disease
organisms to humans in the war-tom Europe, the organophosphorous insecticides were
developed.

Dr. Schrader of I. G. F arben in Germany (1934) discovered that certain
organophosphorous compounds as insecticides. They were initially developed as nerve
gasses for chemical warfare. Their toxic mode of action kills insects and vertebrates by
binding with acetyl cholinesterase in the synaptic junctions of the nervous system. The
resulting effect is a continuous electrical “firing” of chemical signals along the nerve, and
repeated muscle contraction and death by exhaustion. Organophosphates (i.e. azinophos-
methyl) are widely used for fruit fly control in current cherry production systems.

In 1962, Rachel Carson’s book Silent Spring, shook public confidence in
pesticides. She painted a grim picture of environmental consequences of careless
pesticide use. Although the quality of her reporting has been severely criticized, Carson,
more than anyone before, increased awareness to the risks of pesticides. This increased
public awareness has led to a redirection of public policy as well as research toward more
reduced-risk pesticides and cropping methods that reduce the reliance on pesticides.

Since many of the halogenated hydrocarbons, i.e. organophosphates, are being re-
evaluated, restricted or eliminated, it is of utmost concern for researchers to explore
alternative control methods. Therefore, new classes of chemicals with promising
insecticidal properties are being actively evaluated for pest management. Two promising

classes presently being studied in lab and field trials include the neonicotinoids (i.e.

imidacloprid) and naturalytes (i.e. spinosyns). Imidacloprid is a systemic and contact
insecticide developed by Bayer AG of Germany. It has low toxicity to vertebrates and is
seen as a safe alternative to organophosphates and carbamates (CB’s). Imidacloprid
exhibits a wide range of activity against insects, including members of the order Diptera.
Nicotinergic acetylcholine is a neurotransmitter in the synaptic junction of the cholinergic
system of insects, and imidacloprid blocks the binding of this neurotransmitter to its
postsynaptic receptor. Imidacloprid is very stable in the soil, having a half-life of about
150 days. However, it has rapid ultra-violet (UV) break down and is relatively immobile
in the soil and not likely to be a contaminant of ground water.

The spinosyns are a naturally derived group of chemicals produced from the
newly discovered actinomycete species, Saccharopolyspora spinosa. The discovery and
characterization of this soil actinomycete represents a novel opportunity to develop a
portfolio of progressive insect management tools. Spinosad was isolated from an
organism found in soil samples taken in the Caribbean in 1982 by Dow AgroSciences.
To determine its commercial potential, researchers tested the organism and the
metabolites it produced during fermentation. It was discovered that the organism
produced active metabolites that provided excellent insecticidal activity. Spinosad is a
mixture of spinosyn A & D, produced by S. spinosa (Kirst et al., 1992). Spinosad affects
insects in a range of orders, including Diptera. This biological insecticide demonstrates
rapid contact and ingestion activity in insects, which is unusual for a biological product
(Larson et al., 1994). It generally controls pest organisms more rapidly than do

compounds that depend solely on ingestion. This material degrades rapidly in the

10

environment, primarily due to photolysis, and has low toxicity to beneficial insects. It is

a nerve poison; however, and the actual mode of action is unknown.

Histog of Pesticide Regulation. The Federal government first regulated
pesticides when Congress passed the Insecticide Act of 1910. This law was intended to
protect farmers from tainted products. Congress broadened the federal government's
control of pesticides by passing the original Federal Insecticide, F ungicide and
Rodenticide Act (F IF RA) in 1947. FIF RA required the Department of Agriculture to
register all pesticides prior to their introduction in interstate commerce. A 1964
amendment authorized the Secretary of Agriculture to refuse registration to pesticides
that were hazardous or ineffective and to remove them from the market. In 1970,
Congress transferred the administration of F IFRA to the newly created EPA. This was
the initiation of a shift in the focus of federal policy from the control of pesticides for
reasonably safe use in agricultural production, to the control of pesticides for reduction of
unreasonable risks to man and the environment. This new policy focus was expanded by
the passage of the Federal Environmental Pesticide Control Act of 1972 (FEPCA), which
amended FIFRA by specifying methods and standards of control, in greater detail. In
1996, Congress unanimously passed a landmark pesticide food safety legislation
supported by the Administration and a broad coalition of environmental, public health,
agricultural and industry groups. President Clinton promptly signed the bill on August 3,
1996, and the F QPA became law.

The EPA regulates pesticides under two major federal statutes. Under FIFRA, the

EPA registers pesticides for use in the United States and prescribes labeling and other

regulatory requirements to prevent unreasonable adverse effects on health or the
environment. Under the Federal Food, Drug, and Cosmetic Act (F FDCA), the EPA
establishes tolerances (maximum legally permissible levels) for pesticide residues in
food. For over two decades, there have been efforts to update and resolve inconsistencies
in the two major pesticide statutes, but consensus on necessary reforms remain elusive.
The Food Quality Protection Act (FQPA) represents a major breakthrough, amending
both major pesticide laws to establish a more consistent and comprehensive, protective
regulatory scheme, grounded in sound science.

The F QPA charges the EPA with developing and implementing regulations to
enhance protection of the US. food supply from pesticide risks also protection of
agricultural workers, who apply these compounds. A key provision of the Act calls on
the EPA to evaluate pesticide residue risks based on aggregate exposure to all pesticides
that share a common toxicological effect on humans. Initial moves by the EPA raised
concerns in the agricultural community that FQPA implementation might result in sudden
bans on broad classes of pesticides that have been key to US. farm productivity.
However, the EPA has taken a proactive stance to eliminating label uses. The EPA is
allowing some chemistries to remain in use until viable alternatives are available. The
viability of the replacement is often debated, and the EPA is aware of the devastating
impact that wholesale bans of effective chemistries would have.

The EPA’s Office of Pesticide Programs has identified three classes of pesticides
as being high risk to human health, and these are receiving the primary scrutiny under the
FQPA. They include the organophosphate and carbamate insecticides and the group of

broad-spectrum chemicals (known as B-2 chemicals) classified as potential carcinogens.

12

Almost all of these pesticides are used in current cherry (fruit) Integrated Pest
Management (IPM) programs.

Pest management in fruits, vegetables, and both human and animal health
programs offers few alternatives to pesticides. There are no immediate replacements for
the use of CPS, CBs, or 8-2 fungicides for some crops. In addition, the cost of the
alternatives, and the difficulty of related Operational dynamics and adoption complexities
pose a significant threat to the survival of an industry. Under the FQPA, the continued
viability of many minor crops will depend on the ability of growers to transition to new

pest control tools and knowledge-intensive, site-specific IPM programs.

 

In the case of perennial fruit crops, such as cherries, growers might be able to
adopt a range of OP, CB, and B-2 fimgicide mitigation processes including extended pre-
harvest application intervals and post-harvest residue removal processes. Other less
reliable and more complex alternatives, like pest species-specific pheromones to disrupt
insect mating, insect growth regulators, synthetic pyrethroid insecticide substitutes, new
fungicides, and pathogen-resistant varieties, may provide some relief. Yet, established
plantings cannot be changed quickly without high costs, market dislocation, and new
variety acceptance on the part of consumers. Even where some alternatives are available,
many producers may not be able to adapt quickly enough to service these sudden
changes.

Many existing IPM programs have natural and/or augmentative biological control
organisms that have evolved resistance to the OP and/or CB insecticides. Rapid change
from an OP-based IPM program to synthetic pyrethroids may provide an alternative for

some pests, but will likely result in secondary pest outbreaks as natural enemies are

13

killed. Each pest-crop and local/regional crop situation will present a different challenge
for IPM managers. Clearly, alternatives for one pest-crop situation may not be suitable
for another pest, crop, local area, or region.

Where key pesticides are unlikely to be reregistered under the F QPA and where
cancellation is imminent, both the USDA and the EPA are working cooperatively, as
mandated, to ameliorate any short- or long-term dislocation in local crop production and
rural economic stability. This situation will demand a new local-area, alternative IPM
program requiring significant additional public sector support for development and
implementation of replacement IPM programs. In general, the sudden elimination of key
broad-spectrum pesticides that share a similar toxicological effect on humans could cause
serious economic hardship to US. fruit farmers. Especially where few alternatives exist
to the OP, CB, and B-2 fungicides, elimination of one or more of these pesticides groups
could cause production of certain crops to shift away from traditional production regions;
the results may be a shift to imported foods from countries that have less restrictive

agricultural pesticide policies.

Research Obiectives. As Federal mandates on the use of organophosphates
become increasingly more stringent, the need to develop environmentally sound
management programs for cherry fruit flies is of utmost concern. Our research goal was
directed towards developing an improved monitoring system for both species of cherry
fruit flies and finding alternative strategies for reducing the use of organophosphates in
commercial cherry orchard systems. The specific project objectives were 1) To study

insect behavior and refine monitoring programs; 2) To identify reduced-risk compounds

14

 

that can be used in cherry fi'uit fly management programs; 3) To investigate the potential
of integrating biodegradable pesticide-treated spheres and entomopathogenic nematodes
to significantly reduce grower’s reliance on organophosphates.

Our preliminary hypothesis was that improving upon current monitoring
techniques would enable growers to better predict the primary flight of cherry fruit flies,
and infestation levels. This would enable growers to make sound decisions in fruit fly
treatment programs. This, accompanied by reduced-risk insecticides and/or
biodegradable pesticide-treated trapping devices will ultimately reduce reliance and
deposition of harmful and unnecessary spray applications. Furthermore, incorporating
natural enemies, such as entomopathogenic nematodes, would suppress larval and pupal
cherry fruit fly populations, thereby lowering infestation levels in fields. The net effect
of this project will be a new set of pest management strategies for control of cherry fruit

flies.

15

 

CHAPTER ONE

 

VISUAL AND OLFACTORY STIMULII AFFECTING THE RESPONSE OF

CHERRY FRUIT F LIES (DIPTERA: TEPHRITIDAE).

16

 

INTRODUCTION

Passage of the 1996 Food Quality Protection Act (F QPA) and environmental
awareness have provided an impetus for producers, as well as other agricultural
personnel, to reduce the amount of pesticide used on farms throughout the United States.
One of the ways to accomplish this reduction in pesticide usage is to improve monitoring
protocols to detect the presence of key pests, so that pesticides are used judiciously when
pests are present and when alternative management tools are not available.

The eastern cherry fruit fly, Rhagoletis cingulata (Loew), and black cherry fruit
fly, R. fausta (Osten Sacken), are key late-season pests of cultivated cherries, Prunus spp.
in the eastern and midwestem United States. Their larvae develop inside the fruit,
causing major tissue damage. Entire shipments of cherries can be rejected if one or more
maggots are found (Liburd et al., 2001). In order to ensure maggot-free fruit growers,
generally apply broad-spectrum prophylactic sprays on a 2-3 week calendar basis (Edson
et al., 1998). These insecticides are generally effective, but they could potentially affect
non-target organisms, particularly invertebrates in the immediate and surrounding
habitats.

Since the 19805, cherry fi'uit fly IPM programs in Michigan commercial orchards
have relied on visual and olfactory traps for monitoring the presence of adult cherry fruit
flies. Until recently, the standard trap used by most growers has been the Pherocon AM
yellow board (Great Lakes, IPM) deployed in a vertical orientation (Prokopy 1975;
Reissi g 1976). However, in a recent paper, Liburd et al. (2001) showed that an unbaited

three-dimensional Rebel]TM trap (Swiss Federal Research Station, Wadswill, Switzerland)

17

was two times better than Pherocon AM yellow boards in detecting adult cherry fruit
flies. Unbaited Rebellm traps used in their study captured cherry fruit flies 1-2 wk
earlier and were more selective for both eastern and black cherry fruit flies.

In previous studies with the related European cherry fruit fly, Rhagoletis cerasi
(L.), Russ et al. (1973) found that the efficiency of a three-dimensional trap was superior
to that of the two-dimensional Pherocon AM or rectangular boards. Additional
investigations found that daylight fluorescent yellow was also highly attractive to R.
cerasi. 3

Rhagoletis cingulata and R. fausta respond differently to host stimuli. Howitt a

 

(1993) found that R. cingulata prefers to forage and oviposit in sweet cherries P. avium.
Whereas R. fausta favors sour cherries (P. cerasus). Smith (1984) recorded a preference
for fruit compared with leaves for R. cingulata, while Prokopy (1976) noted that R. fausta
spends more time on the leaves compared with the fruit of host plants.

In addition to preferences for host species, other factors are known to affect the
behavior of tephritids. Recently, Thornton and Liburd (1999) noted that various habitat-
associated factors, including the abundance of wild hosts and rainfall, affected the
number of R. cingulata found in cherry orchards in northwestern Michigan. Other
studies have shown that the state of susceptibility of the fruit affected the ability of R.
mendax Curran to oviposit in blueberries (Liburd et al., 1998). Moreover, in apples, the
ripening phenology and degree of hardness affected the oviposition rate of R. pomonella
(Messina and Jones 1990). Roitberg et al., (1982) and Averill (1996) found that the

presence of oviposition scars decreased R. pomonella’s decision to oviposit into fruit.

18

Our objective was to study the visual and olfactory responses of R. cingulata and
R. fausta using baited and unbaited Rebellm traps. This goal was to build upon previous
research by improving monitoring efficacy and determining the effects of host stimuli on
the abundance of cherry fruit flies. The specific objectives were to: 1) to determine
whether baiting RebellTM traps would increase the captures of cherry fruit flies, and
2) Determine the roles of fruit and foliage in attracting black cherry fruit flies to

commercial orchards.

l9

‘1.- ‘. 7818‘ .

 

MATERIALS AND METHODS

Rebellm Experiment. Experiments to evaluate baited versus unbaited RebellTM traps
were conducted at the Michigan State University Northwest Horticultural Research
Station (NWHRS), in Traverse City, Michigan, and at an abandoned sour cherry, P.
cerasus, orchard in southwestern Michigan. At the NWHRS, the experiment was
conducted from 1 July to 25 August 2000. In southwest M1, the experiment was
conducted from 29 May to 2 July 2001. Each experimental site consisted of a 3-hectare
block of non-sprayed cherries. The NWHRS site has a dominant residential population
of R. cingulata, whereas the southwestern site has a high resident population of R. fausta
(Liburd et al., 2001).

Prior to deploying RebellTM traps in the orchard, all traps were washed with
Histoclear® (Great Lakes IPM, Vestaburg M1) to remove tangle-trap, rinsed twice with
distilled water, and allowed to air dry. The traps were then sprayed with a thin layer of
insect Tangle-Trap® (aerosol formula, Tanglefoot Company, Grand Rapids, MI). Baited
traps had a green polycon dispenser containing 5.0 g of ammonium acetate attached to
the top surface of the trap.

The experimental design was a randomized complete block with four replicates.
Traps were hung within the center of the tree canopy and spaced 20 m apart within rows,
and approximately 30 m between blocks. The foliage immediately surrounding the traps
was cleared to prevent any interference between the traps and tree canopies (Drummond

et al., 1984). All traps were rotated within blocks on a weekly basis (Fig.1).

20

 

Four treatments consisting of the three—dimensional RebellTM trap were evaluated:
1) baited yellow Rebellm; 2) unbaited yellow Rebellm used by Liburd et al., (2001); 3)

unbaited transparent (made from plexiglas) Rebellm; and 4) baited transparent Rebellm.

Fruit versus Foliage. Experiments to investigate the relationship between host
plant characteristics and the abundance of black cherry fruit flies were conducted at the
sour cherry, P. cerasus, site adjacent to our abandoned cherry fi'uit fly RebellTM trap
experiment in southwestern, Michigan. A one-hectare block of unsprayed cherries was

used for this experiment. The experimental design was a completely randomized design »

 

with four replications. Three treatments were evaluated: 1) cherry trees with fruit and
foliage, 2) cherry trees with fruit and no foliage, and 3) cherry trees without fruit, but
with foliage. Cherry trees without leaves and with fi'uit were defoliated manually prior to
the start of the experiment. Our defoliation process continued on a weekly basis to
ensure there was no leaf growth. Trees with leaves and without fruit were de-fruited in a
similar fashion to our leaf defoliation process. An unbaited Rebellm trap was hung in the

center of the each test tree canopy to monitor fly population.

Sampling. R. cingulata and R. fausta caught on traps were counted by sex two
times per week, and trapped flies were removed. Female flies caught on traps were
classified as mature or sexually immature after thorough examination of the rear

abdominal segments.

21

Statistical Analysis. Data from all experiments were square-root transformed
(x + 0.5) and then subjected to an analysis of variance (SAS Institute 1989). Least
Significant Difference Test (LSD) was used to identify differences in treatment means

(P g 0.05). The untransformed mean values are presented in the Tables and Figures.

 

22

RESULTS

Rebellm Experiment. 2000. In experiments to investigate the visual and
olfactory responses of R. cingulata, significantly (F = 77.2; df = 3, 9; P < 0.01) more
cherry fruit flies were caught on the baited Rebell1m traps compared with the other traps
tested (Fig. 2). Baited RebellTM traps captured 1.8, 8.6, and 18.8 times as many R.
cingulata as the unbaited Rebell“, baited transparent, and un-baited transparent Rebell
traps, respectively (Fig. 2). The unbaited Rebell” trap (standard) caught significantly
more R. cingulata than the baited or unbaited transparent traps. On an average, unbaited
traps captured 4.9 times as many flies than the transparent traps (baited and un-baited)
(Fig. 2).

During the 2000 field-season, the first R. cingulata was captured on June 30 and
peak activity was recorded on July 10 (Fig. 3). After July 10, R. cingulata activity
declined rapidly and no flies were caught after August 25 (Fig. 3). Yellow RebellTM traps
(baited and unbaited) captured significantly (F = 42.9; df = 1,3; P < 0.01) more R.
cingulata females than males (Table 1). Both baited and unbaited yellow RebellTM traps
caught 2.6 and 3.7 times as many females as males, respectively (Table 1). More than
70% of females caught were sexually mature. There were no significant differences for
females and males between baited and unbaited transparent Rebell” traps (Table 1).

2001. The responses of R. fausta to baited and un-baited Rebell“ traps differed
from those observed for R. cingulata. There was no significant difference between baited
and unbaited (standard) yellow RebellTM trap captures (Fig. 4). However, these two traps
(baited and unbaited yellow Rebell“) captured significantly (F = 12.5; (if = 3,9; P <0.01)

more flies than transparent traps (Fig. 4). On average, baited and unbaited yellow traps

23

“an

 

 

 

caught 13.8 times more flies as transparent Rebell” traps (Fig. 4). There were no
significant differences between baited and unbaited transparent traps (Fig. 4).

Rhagoletisfausta began emerging on May 24 when 3 three flies were caught on
baited RebellTM traps (Fig. 5). Trap captures quickly increased and peaked within three
weeks on June 14 (Fig. 5). An average of 140 and 160 flies were captured on baited and
unbaited Rebellm traps, respectively (Fig. 5). After peak emergence, fly captures
declined slowly and no flies were captured after July 4 (Fig. 5). Both baited and unbaited
yellow Rebellm traps captured significantly (F = 19.2; df = 1,3; P < 0.01) more females
than males R. fausta (Table 2). Approximately 75% of the females caught were sexually
mature. There was no significant difference in ratio of female to male captures of R.
fausta with baited and unbaited transparent Rebell traps (Table 2).

Fruit and Foliage. Our results showed that sour cherry trees P. cerasus with
adequate fruit and leaves were significantly (F = 12.0; (if = 2,6; P < 0.01) more attractive
to R. fausta than trees that had fruit but no leaves, or trees that had leaves but no fi'uit
(Fig. 6). Unbaited yellow Rebell” monitoring traps placed within cherry trees with fruit
and foliage caught 1.5 and 31.5 times as many flies as traps placed in trees with fi'uit but
no leaves and no fi'uit but with leaves respectively (Fig. 6). Trap captures were also
significantly (F = 16.2; df = 2,6; P < 0.01) more abundant for R. fausta in cherry trees
that had fruit but no leaves compared with trees with no fruit but with leaves. Traps
placed in sour cherry trees deprived of leaves (with an abundant fruit supply) captured

16.5 times as many flies as traps placed in trees without fruit but with leaves.

24

 

DISCUSSION

Response of Cherry Fruit Flies to Rebell“ Traps. Findings indicate that
ammonium acetate-baited yellow Rebell” traps were considerably more effective in
detecting the presence of eastern cherry fruit flies compared with other traps evaluated in
the study. Possible implications of these observations on baited versus unbaited yellow
Rebellm traps and the two species of cherry fruit flies have interesting trends in relation
to host and fly maturity. A major concern regarding ammonium-baited traps is that they
attract non-target organisms (Liburd et al., 2000, Drummond et al., 1984), which may be
important in regulating cherry fruit fly populations.

Although there was hardly any attraction of R. cingulata to baited transparent
RebellTM traps, adding a visual (yellow color) stimulus significantly increased trap
captures above the stande unbaited yellow Rebell”, which may suggest that both visual
(yellow) and olfactory (bait) stimuli are responsible for the increased attraction of R.
cingulata to the baited yellow RebellTM traps. Previous work by Liburd et al., (2001)
investigated the potential for using unbaited yellow RebellTM traps for monitoring R.
cingulata and R. fausta populations.

In our studies, R. fausta responses were different from those of R. cingulata. The
fact that both baited and unbaited yellow RebellTM traps were considerably more attractive
to R. fausta than transparent (baited and unbaited) traps suggests that color is more
important than odor. Yellow color plus ammonium acetate bait may act synergistically in

one species (Eastern) but not synergistically in the other (black). Daylight fluorescent

25

 

yellow has previously been shown to be the principal attractant influencing the response
of the related European cherry fruit fly, R. cerasi, to three-dimensional trapping devices
(Russ et al., 1973).

Evidence for behavioral differences between R. cingulata and R. fausta have been
reported earlier by Liburd et al., (2001). In their studies, R. fausta trap captures for the
unbaited yellow RebellTM traps were higher than several types of baited and unbaited
commercial traps they evaluated. When the same study was repeated with R. cingulata,
captures from unbaited yellow RebellTM traps were not significantly different from baited
yellow boards and red spheres, demonstrating clear behavioral differences between the
species. Our study supports the hypothesis that R. cingulata is highly responsive to
ammonium baited yellow RebellTM traps, whereas with R. fausta there is no statistical
difference between ammonium-baited RebellTM traps and the standard Rebell” trap.

Approximately 2.8 times as many females compared with males were caught
throughout the season. I presume that more sexually mature females were caught on
yellow RebellTM traps because they are moving into commercial cherry orchards where
abundant resources are available for oviposition and larval development. Sexually
mature females are probably moving into commercial orchards from adjacent woodlands
where wild hosts may be limited.

It is important to note the difference in peak trapped populations for the eastern
cherry fruit fly (Fig. 3). Populations peaked approximately 7 July for baited Rebell”
traps, and then dropped off through the end of the season. Interestingly, trapped
populations were rapidly declining for the baited Rebell”, while increasing for yellow

unbaited Rebell” traps. This raises the question of the bait potentially being a feeding

26

 

deterrent at this point in time of R. cingulata development. Laboratory assays to study R.
cingulata behavior is recommended to investigate this observation.

In this study, there was evidence that females may be better at detecting color
than males. This was clearly demonstrated when no differences between females and
males captures for the transparent Rebell" traps were detected while significantly more

females than males were captured on yellow Rebellm traps.

Fruit and foliage. In studies investigating the effects of presence or absence of
fruit and leaves, we found that a greater number of flies were foraging in trees that had an
abundant supply of fruit and foliage. Host fruit provide adequate resources for egg
deposition and larval development for Rhagoletis species, and leaves provide sites for
feeding and shelter (Prokopy 1976). When both fruit and leaves are in abundant supply,
they provide optimum resources for R. fausta diurnal activities. This was evident in our
studies since host trees without fruit and with an abundant supply of leaves had
considerably fewer flies on traps. Previous studies have indicated that R. fausta visit
leaves more frequently than fruit (Prokopy et al., 1976). However, our work indicates
that fruit is more important than leaves to sustain a high population of R. fausta flies.
Fruit maturity, fly maturity, temperature and rainfall can also affect the number of flies
foraging in cherry orchards (Thornton and Liburd 1999).

These results have important implications with respect to monitoring cherry fruit
fly populations. When researchers, growers and agricultural extension personnel are
developing monitoring protocols for R. cingulata in cultivated cherries, they should

consider using an ammonium bait to improve early detection of R. cingulata. In

27

Michigan, these baited yellow RebellTM traps should be deployed in mid-June prior to R.
cingulata emergence. However, since there is no significant response difference of R.
fausta to baited yellow Rebell“ traps and the standard Rebell traps, growers can
implement the standard unbaited yellow Rebell” traps for monitoring R. fausta
populations. These unbaited yellow RebellTM traps should be deployed in Michigan

cherry orchards during mid-May before R. fausta emerges.

 

28

Table 1. Comparison of total male and female Rhagoletis cingulata captures on four

types of traps, Traverse City, MI (2000).

 

Mean no. of Rhagoletis cingulata captured :5 SEM

 

 

Treatments Females Males

Baited Rebell“ 182.5 a 19.7a1 70.3 :1; 3.9b
Rebell“ 115.0 :1: 19.7a 31.3 i 6.2b
Baited Transparent 20.5 i 3.8a 12.8 i 0.8a
Transparent 13.5 i 7.4a 7.0 :t 3.1a

 

 

1Row means followed by the same letter are not significantly different
(P = 0.05, LSD test).

2 Statistical analyses were done on the square-root transformed data.

29

Table 2. Comparison of total male and female Rhagoletisfausta captures on four types

of traps, Paw Paw, MI (2001).

 

Mean no. of Rhagoletis fausta captured :t SEM

 

 

 

Treatments Females Males
P
Baited Rebellm 503.0 3: 55.12211 90.5 i 16.1 b
Rebell“ 587.3 :1: 18.6 a 101.0 :1: 21.6b
Baited Plexiglas 41.3 i 2.7 a 6.1 :I: 2.2 a
Plexiglas 13.8 i 2.9 a 4.3 :1: 2.2 a

 

lRow means followed by the same letter are not significantly different
(P = 0.05, LSD test).

2 Statistical analyses were done on the square-root transformed data.

30

Trap Type

BR = Baited Rebellm

R = Rebell“

BT = Baited Transparent
T =Transparent

 

 

 

 

Rep 1 Rep 2 Rep 3 Rep 4
Blk 1 Blk 2 Blk 3 Blk 4

T‘ i i T

 

 

w

..j
w
76
W

<—»—a

 

 

 

 

 

 

 

 

Fig. 1. Completely randomized block design for modified RebellTM experiment;

treatments rotated within block on a weekly basis.

 

 

300

 

 

 

     

a
250 .
a.
2
1- 200 —
B
.2
E 150 ~
6
z
c 100 a
5
£
50 - C
c
O _
Baited Unbaited Baited Unbaited
Transparent Transparent

Fig. 2. Total Rhagoletis cingulata captures 1 July — 25 Aug. on four types of
modified RebellTM traps, Traverse City, Michigan (2000).

(F = 77.2; df= 3, 9; P < 0.01)

32

MeanNo.Flies/Trap

8

{5‘

§

8

 

 

 

1/0 6/30 7/7 7/ 14 7/21 7/28 8/4 8/1 1 8/ 18 8/25

 

 

-+-Ba'tedRebellT“ —l—Rebell““ +BaitedTranspaent -X-Transpanent

 

 

Fig. 3. Comparative population dynamics of Rhagoletis cingulata as measured by
four trapping systems in a Traverse City, MI cherry orchard in 2000.

(F = 42.9; df= 1,3; P < 0.01)

33

 

1000

 

 

       

a.
E 800 a
B
é’ 600
LI.
0'
z 400
Z
8
2 200 b b

0 .

Baited Unbaited Baited Transparent
Transparent

Fig. 4. Total captures of Rhagoletisfausta 24 May — 4 July on four types of
modified Rebell” traps, Paw Paw, MI (2001).

(F: 12.5; df= 3,9; P < 0.01)

34

 

 

 

§§§§§

MeanNo. Flies/Trap

 

 

o8888

 

 

 

—<>—Baited mum -I- FbebellTM +Baited Transpaent *Trarspaentl

Fig. 5. Comparative population dynamics of Rhagoletisfausta as measured by
four trapping systems in a cherry orchard, Paw Paw, MI 2001.

(F=19.2;df=1,3;P< 0.01)

35

Mean No. Flles I T

700

600

500

400

300

200

100

 

 

 

 

 

Fruit and Leaves

 

Fruit

C

 

Leaves

Fig. 6. Attraction of Rhagoletisfausta to Rebell” traps in cherry trees,

Prunus cerasus, Paw Paw, MI (2001).

36

—___.

1 ‘ll ‘14“ uh.“

 

CHAPTER TWO
EVALUATION OF REDUCED-RISK INSECTICIDES AS ALTERNATIVES TO
ORGANOPHOSPHATE INSECTICIDES FOR CONTROL OF CHERRY FRUIT

FLIES (DIPTERA: TEPHRITIDAE)

37

 

INTRODUCTION

The safety of pesticide application is a major concern for commercial cherry
growers in Michigan. As a group, cherry growers in this region have been proactive,
with the aid of research scientists at Michigan State University, in their approach to
environmentally sound cultural and pesticide pest management practices. Michigan is
currently the leading world-wide producer of tart cherries, Prunus avium L.

Approximately 75 percent of the nation’s cherry production originates in
Michigan, traditionally known as the “cherry capital of the world” (Michigan
Agricultural Statistics 1999). To ensure pest and residue-free fruit to meet federally
mandated zero tolerance levels, two to three applications of organophosphate insecticides
are used in cherry orchards to control major economic pests, including the eastern,
Rhagoletis cingulata (Loew) and black, R. fausta (Osten Sacken) cherry fruit flies (Edson
et al., 1998). Cherry fruit flies pose a threat to commercial cherry production in
Michigan, in terms of domestic fruit quality and in the states share of the national cherry
market. A major concern with organophosphates (OP’s) used for pest control is that they
kill not only pest organisms, but also non-target organisms, thus indiscriminately harming
our natural resources.

Pest management is an integral part of agriculture. It brings world wide benefits
to people, increasing both the quantity and quality of crops grown. Pesticides are
commonly used in pest management. Their benefits obviously need to be delivered
without posing unacceptable risks to non-target organisms. Thus, the potential risks,

which are a function of both toxicity and exposure, need to be determined to ensure

38

 

pesticide safety. The 16th Century Swiss Physician, Paracelsus, said that it is “the dose
that makes the poison”. That exposure is a crucial element of risk was understood well
before the modern advent of pesticides. Potential risks, however, are sometimes assessed
and managed more by ranking their degree of toxicity, particularly where environmental
fate data are lacking.

The discovery, development, registration, and commercial introduction of new

pesticides for control of insect pests including cherry fi'uit flies, is a lengthy and

I a. Hm,

expensive process. A significant amount of screening and targeted molecular design r

occurs in the identification of patentable chemistries with novel modes of action. Once a

 

decision is taken to develop a new active ingredient, a major testing phase focused on
field performance, health and environmental safety, manufacturing optimization, and
commercial planning is initiated. This may last from three to five years, after which time
a regulatory review period of anywhere from one-and-a half to four or more years occurs.
For every new active ingredient that enters development, there may be 20,000 or
more candidate compounds and analogues that will have been screened for biological
activity. Discovery and development phases are collectively both costly and time-
consuming, and it may take five to ten years after entry into the marketplace for the
original investment to be recovered. The cost of bringing a single product to the
marketplace from discovery through launch may be $50 to 60 million or more. Thus,
even a single year delay in reaching the marketplace can be very costly in terms of value
recovery and patent protection. By using discounted cash flow analysis, it has been
estimated that a one-year delay in registration approval and product launch may reduce

the value of a new pesticide product by $5 million (Leng 1991).

39

Regulatory trends during the past decade or more have focused an inordinate
degree of attention and an increasing level of resources on re—evaluation of older
pesticides. Both technical and societal issues have driven the ever-increasing levels of
regulatory scrutiny and increased pesticide registration requirements. Recent examples
include interest in potential endocrine effects, acute dietary intake assessment, and

ground and surface water contamination. In addition, political factors have yielded

 

I.
increased demands on the pesticide registration process. An example of this in the US. is .
the Clinton Administration’s “Children’s Health Initiative”, which has driven highly T
conservative and restrictive approaches for pesticide evaluation despite lack of i

compelling evidence that children in the US. are at any undue risk of adverse effects
from the use of pesticides (Huebner and Chilton 1998). The result of such increased
scrutiny, which often has been generated by issues related to older products, is that it has
become more difficult and expensive to register new products. The Environmental
Protection Agency (EPA) is currently focusing on reducing pesticide use as a national
priority. Furthermore, authorities have also been involved in comprehensive re-
evaluation or re-registration programs focused on older chemicals. These programs are
designed to review the safety aspects of existing pesticides in light of current data
requirements and stringent assessment procedures.

Michigan cherry growers have strived to reduce use of insecticides to control
cherry fruit fly through the implementation of alternative control strategies. Although
this effort has brought some success, the pest management systems still relies primarily
on organophosphate insecticides. Michigan cherry growers need economically viable

and ecologically sound alternatives to organophosphate insecticides that will effectively

40

control cherry fruit fly and meet the stringent quality demands of the marketplace and
government regulations. Zero tolerance is an extremely stringent standard. Even if
growers continue to use organophosphate insecticides, there is a limit as to how far they
can realistically (economically) reduce use, based solely on requirements that no cherry
fruit fly larva be present in the fruit at harvest.

Current research trends have led to the findings and development of novel
“reduced-risk” chemistries. The general principle of EPA’s pesticide registration
program in the US. is to give registration priority and accelerated approval to products

with the most favorable characteristics (i.e. reduced-risk) as compared to conventional

chemistry alternatives. The overall objective is to accelerate the introduction of reduced-
risk products so that marketplace choices rather than increased regulatory restrictions can
lead to replacement of older products and technologies. Under the program, pesticides
classified as reduced-risk products must meet several or all of the following criteria as
compared with currently available alternatives (US. EPA 1997): a) reduced risks to
human health and non-target organisms; b) reduced potential for contamination of valued
environmental resources (water, air, soil); c) broadened adoption of Integrated Pest
Management (IPM). Reduced risk pesticide programs were first envisioned during the
late 1980’s and early 1990’s. In 1992, public comments were invited on a proposed
program for providing regulatory incentives for development of safer pesticide products.
During 1993, a voluntary reduced risk pesticide initiative was introduced which described
interim criteria for reduced-risk active ingredients, guidelines for submission of reduced
risk rationale by registrants, and a streamlined registration process. By 1997, more

detailed guidelines were promulgated for expedited regulatory review under the reduced-

41

risk program (U .S. EPA 1997), including adoption of formalized reduced risk criteria, a
standardized submission format, and establishment of a Reduced Risk Committee at the
EPA. During 1998, the EPA established a priority system of review for all registration
submissions, with several categories of reduced-risk products adopted by the Agency as
top priorities for registration review. In addition to first-time registrations of new active
ingredients, the program was expanded in 1996 to include accelerated registration
approval for additional crops and uses for active ingredients already classified as reduced
risk.

As Food Quality Protection Act (FQPA) regulations lead to a reduction in the use of
organophosphate insecticides, and public pressure against the use of broad-spectrum
insecticides increases, it becomes necessary to identify effective non-organophosphate
compounds for inclusion into novel pest management tactics. The objective of this study
was to investigate the efficacy of novel chenristries as control alternatives to
organophosphates (i.e. Guthion) for residential cherry fruit fly populations within orchard

systems.

42

MATERIALS AND METHODS

Insecticide Trials. 2000. Experiments to evaluate the effectiveness of different kinds of
insecticides on cherry fruit fly species were conducted in an abandoned sweet cherry

(P. avium) block in Leelanau County, Michigan. The experiment began on 1 July, and
was terminated on 25 August 2000. The experimental site consisted of a 2.05-acre block
of non-sprayed cherries. The site has a dominant residential population of R. cingulata
flies.

The experimental design consisted of a completely randomized block with four
replicates. Plot size was approximately 3200 sq. ft. consisting of 5 x 5 trees (25 plants)
spaced approximately 10 m within rows and 20 m between blocks. Fly populations were
monitored by using baited Rebell” traps (Swiss Federal Research Station, Wadswill,
Switzerland). Baited traps had a green polycon dispenser containing 5.0 g of ammonium
acetate attached to the top surface of the trap. The foliage immediately surrounding the
traps was cleared to prevent any interference between the hung traps and the tree canopy
(Drummond et al., 1984). Insecticide applications were applied after detection of hit fly
emergence. Seven treatments were applied with a Friend Airblast Sprayer (Air-O-F an,
Reedley, California). Fly emergence was detected on 22 June 2000 (Fig. 7). The first
application was made on 28 June 2000, and a second was made on 8 July 2000: 1) the
Naturalyte, SpinTor® 2 SC (Spinosad; 22.8% a.i.; Dow AgroSciences, Indianapolis, IN)
at a rate of 6.0 oz/acre; 2) SpinTor Bait® GF 120 (0.02% a.i. bait) 52.0 oz./acre; three
compounds of the neonicotinoid class, including: 3) Provado® 1.6 F (imidacloprid; 17.4%

a.i.; Bayer, Kansas City, Missouri) at a rate of 8.0 fl oz/acre, 4) Calypso® 480 SC

43

(thiacloprid; 40.4% a.i.; Bayer Corp.) at a rate of 3.0 fl oz/acre, and 5) Actara® 25 WG at
a rate of 4.5 oz/acre; 6) the conventional organophosphate, azinophos-methyl (Guthion®
50 WP (azinphos-methyl; 50% a.i.; Bayer Corp.) at a rate of 1.5 lbs/acre; and 7) an
untreated control. An organo-silicant, Slygard® 309 (Diatect International Inc., Smith
Center, Kansas) was added to SpinTor® 2 SC and SpinTor Bait® at a rate of 40 L / ha.
The addition of Slygard® 309 allowed for a more uniform distribution of spray droplets
on cherry trees. Experimental plot was sprayed with a fungicide, consequently no disease

was detected.

 

Monitoring. Each RebellTM trap was monitored for R. cingulata, and flies were
removed twice per week. Female flies were classified as sexually mature or immature by
thorough examination of the rear abdominal segments. Fruit infestation levels were
monitored by collecting 200 cherries per treatment. They were placed over 0.5-cm
hardware-mesh screens with containers below. Cherries were left on hardware mesh for
three weeks at room temperature. Containers were examined on a daily basis for maggot

emergence.

Laboratory Bioassays. 2001. Bioassays were conducted at our laboratory in the Center
for Integrated Plant Systems at Michigan State University, East Lansing, Michigan.
Single-Dose assays were conducted to study the behavioral response of sexually mature
female flies (R. fausta) to selective compounds, and the conventional organophosphate

control method, azinophos-methyl.

44

Fly Preparation. Cherries were collected from unsprayed farms in southwestern
Michigan during the summer of 2000 and placed on 0.5-cm mesh hardware cloth (ACE
Hardware, East Lansing, M1) for 21 days over collecting trays containing vermiculite
(Liburd et al., 1998b). Emerging puparia were collected from trays daily during the 21
day period and maintained at 5° C for approximately 9 months. Approximately 50 days
prior to the start of the bioassays, puparia were placed in 60 x 60 x 60 cm stainless steel
collapsible insect cages (BioQuip, Gardena, California) in shallow (2-cm deep) plastic
containers with moist vermiculite. Puparia were kept moist by spraying water with an
atomizer at 24° C and exposed to day length of 16 light:8 dark hours and 70% RH. After
35 days, cherry fruit flies began to emerge. Upon exclusion, newly emerged flies were
provided with water and strips of cardboard coated with a mixture of yeast hydrolysate
(enzyrnated autolyzed Brewer’s yeast; 1 CN Biomedicals Inc., Costa Mesa, California),
water, and honey. All flies, R. fausta, used in assays were tested when they were 10 days
old because by that time they were believed to have mated and be reproductively mature

(Hu and Prokopy 1998).

Single-Dose Response Assay. The following six treatment rates were used:

1) Naturalyte insecticide, SpinTor® 2 SC at a rate of 100 1.11 in 200 ml distilled water;

2) SpinTor Bait® at a rate of 1ml in 2ml distilled water; 3) Provado® 1.6 F at a rate of
100ul/ 160 ml distilled water; 4) Calypso® 480 SC at a rate of 100ul / 400ml distilled
water; 4) conventional organophosphate, Guthion 50 WP applied at a rate of 1.0 g / 400
ml distilled water; 6) untreated control. All treatments were mixed with SUN Ultra Fine

Oil surfactant (Sun Refining and Marketing Co., Philadelphia, Pennsylvania) at 1% v/v

45

and administered at rates equivalent to field application by proportionate scaling of large
quantity recipes.

Cherry cuttings from sour cherries with immature (green) fruit were obtained
from an abandoned orchard in Paw Paw, Michigan in May 2001. Cherry shoots were
homogeneous among replicates with 10 fruit of similar ripeness and repeatable foliage
densities. Shoots were placed in transparent food containers (946 ml) with lids (SOLO
CUP Company, Urbana, Illinois) were held turgid with moistened Oasis Floral Foam
(Hyacinth House Greenery, Lansing, Michigan). Four flies per treatment (one fly per
replicate) were introduced into the bioassay chambers. Food was provided in each
chamber, and consisted of a mixture of yeast hydrolysate, honey, and water. Pin-sized
holes were made in the lids of each container to allow fresh air to enter bioassay
chambers. Cherry fruit flies were released into chambers and allowed to feed. Feeding
duration was defined as time cherry fi'uit flies spent alighting on cherry cuttings while
exhibiting proboscis extension. Observations to determine mortality were made during

the 10-minute feeding bout, as well as 1 and 24 hours after feeding.
Statistical Analysis. Data from all experiments were square-root transformed (x + 0.5)

and then subjected to an analysis of variance (SAS Institute 1989). Least Significance

Test (LSD) was used to identify differences in treatment means (P 5 0.05).

46

 

RESULTS

Insecticide Trials. 2000. On July 18, fruit infestation levels were significantly

(F = 11.3; df = 6,9; P < 0.001) greater in the untreated control plots compared with the
rest of the treatments (Fig. 8). Fruit taken from plots treated with Actara®, Provado®,
Calypso®, and Guthion® had 7 times fewer maggots than the untreated control. Plots
treated with SpinTor® and SpinT or Bait® had 3 times fewer maggots than the control,
these plots had significantly more maggots than Actara®, Provado®, Calypso®, and

Guthion®. There was no significant difference between SpinTor® and SpinTor Bait®.

 

Our final fruit sample on July 28 showed significantly (F = 6.31; df = 6,9; P < 0.01 )
more maggots in the untreated control plots compared with the other treatments (Fig. 9).
Apart from the control, there was no significant difference among the other treatments.
SpinTor®, however, had interesting results. In the first fruit analysis, there were
significantly more larvae than both neonicotinoid and organophosphate treated plots.
However, in the second fruit analysis (July 28) no significant difference was detected

between SpinTor® and both neonicotinoid and organophosphate treated plots.

Laboratory Bioassays. 2001. After 10 minutes of feeding, significantly

(F = 10.4; (if = 5,8; P < 0.001) more cherry fruit flies were killed by fruit clusters treated
with Calypso®, Provado®, and Guthion®,‘ compared with SpinTor® and SpinTor
Bait®. Twenty-four hours after the initial ten-minute feeding period, 100 % mortality

was achieved among all chamber treatments (Fig. 10). No mortality was observed in the

47

flies that alighted and fed upon the untreated control chambers 24-hours after exposure

(Fig. 10).

48

DISCUSSION

Experimental findings suggest that the neonicotinoid insecticides tested may be
effective alternatives to conventional organophosphates for control of Rhagoletis
cingulata. Fruit infestation analysis demonstrated that neonicotinoid insecticides were as
efficient as conventional (organophosphate) control methods, though pest pressure was
low to moderate. The two Spinosad formulations also were promising, though higher
rates or more sprays may be needed to achieve enhanced control.

Laboratory bioassays provided similar data to those obtained in the field and
helped explain some of the differences and changes in effectiveness that were observed
over the course of the growing season. The assays showed that neonicotinoid insecticides
were second behind Guthion® in killing fruit flies, with 100% mortality reached after 1
hour of exposure. Neonicotinoids were an effective means of controlling cherry fruit
flies, though more time was needed to attain lethal activity compared to Guthion®. The
naturalyte compounds (SpinTor® and SpinTor Bait®), were effective as well, but required
substantially more time to kill than the neonicotinoids, thus indicating a positive
correlation between field and laboratory trials.

These results are promising alternatives to organophosphates. While many
insecticides are under review, and zero tolerance levels for maggot infested fruit remain,
it is imperative to continue research on alternatives to control cherry fruit flies.

The reduced-risk program is by no means a panacea. Not all reduced-risk
pesticides, having been afforded regulatory priority of effort, have become successful
commercial products. In addition, not all reduced-risk products will necessarily pose less

risk than current alternatives for all use patterns and in all circumstances. The concept of

49

reduced risk involves a relative comparison; an active ingredient may be considered
reduced risk for some uses but not for others. Finally, the fact that a new or existing
product has not achieved reduced-risk product status should not be construed as an
indication that these types of products necessarily pose greater risks. The actual risk
posed by the use of any pesticide product, whether it has been approved as a reduced-risk
product or not, is a function of many factors including formulation type, method of
application, use of protective clothing, and environmental variables.

We live in a world of choices when it comes to establishing the priorities of
individual regulatory processes. As has generally been the case, massive investment of
resources can continue to be devoted to cycles of data evaluation, regulatory re-
evaluation and re-registration, and imposition of increased restrictions for the many older
products currently employed in pest management programs. Some measure of attention
to these older products is obviously warranted. However, with the continued limitation
of resources in both the government and industrial sectors, an undue emphasis on the old
may not allow sufficient resources to be directed to support the timely approval and
market availability of the next generations of pesticides. The accelerated review and
approval of new products with enhanced safety and environmental profiles is a proactive
and positive step which will hopefully unleash marketplace forces to accelerate the
replacement of older pesticide products. It is also an endeavour that places regulatory
agencies and manufacturers in a collaboration which is of benefit to both pesticide users
and detractors. Where we place our emphasis and energy in coming days, on the old or
the new, will determine to a great extent how soon the world may have unfettered access

to the safest and most desirable pest management tools.

50

140
120

100 A
80 / \
60 I

.0 /

2: J

 

 

 

 

 

 

Mean No. Flies I Trap

 

 

 

i

6/15
6/22 ‘
6/29 ‘
7/6 ‘
7/13 ‘
7/20 ‘
7/27
8/3 ‘
8/10 ‘
8/17 ‘
8/24

Fig. 7. Population dynamics of Rhagoletis cingulata caught on baited RebellTM traps in

an abandoned cherry orchard in Leelanau County, MI (2000).

51

 

 

 

 

 

 

 

 

 

% of Infested Fruit

 

 

 

 

 

Actara Provado Calypso Gutlr'on SpinTor SpinTor Bait UTC

Fig. 8. Influence of six insecticides on Rhagoletis cingulata infestation of cherry fruit as
measured on 18 July 2000 in a cherry research plot in Leelanau County, MI .

(F =11.3;df= 6,9; P < 0.001)

52

(O

 

CD

 

N

 

O)

 

O'l

 

A

 

% of Infested Fruit

00

 

 

 

 

 

 

Adara Provado Caypso Gution Sp'nTor Sp'nTor Ba't UTC

Fig. 9. Influence of six insecticides on Rhagoletis cingulata infestation of cherry
fruit as measured on 28 July 2000 in a cherry research plot in

Leelanau County, MI. (F = 6.31; df= 6,9; P < 0.01)

53

 

% Fly Mortality

120 ~

80*

60-

A
o
1

2

O

 

O

_ illli‘l /A

Provado

ll
1111113.

Calypso

Guthion

.ljlr fill
all (311‘
“ll .1
1‘1 A ‘3‘: A

SpinTor
Bait

SpinTor

 

 

, m 10 Minutes

I1 Hour
l 24 Hours

 

 

UTC

Fig. 10. Percent fly mortality (Rhagoletisfausta) exposed to different

insecticides in bioassay chambers, Michigan State University, MI 2001.

54

 

CHAPTER THREE

 

EVALUATION OF BIODEGRADABLE, INSECTICIDE TREATED TRAPPING
DEVICES AND ENTOMOPATHOGENIC NEMATODES FOR CONTROL OF

CHERRY FRUIT FLIES, RHA GOLETIS Spp.

55

INTRODUCTION

The larval stages of two native tephritid flies feed on fi'uit in cultivated
cherries are the eastern, Rhagoletis cingulata (Loew) and the black cherry fruit
fly, R. fausta (Osten Saken). These have a major negative impact on the cherry
industry. There is a zero tolerance among cherry growers, packers, consumers
and international markets for cherries infested with maggots. Michigan
Department of Agriculture inspectors constantly monitor packinghouses and
sample cherry lots for cherry maggots. If a single maggot is detected, the
packinghouse is shut down to dispose of all cherries that may be infested (Liburd

et al., 2001). This is often a lengthy and costly process.

To meet the zero tolerance for maggot-infested fruit, commercial growers rely on
insecticides to protect their crop from cherry fruit flies (Edson et al., 1998).

Conventional broad-spectrum organophosphate insecticides are used. These are highly
toxic chemicals and can threaten non-target organisms, particularly invertebrates in the
immediate and surrounding habitats. Currently, most commercial cherry growers apply
two to four foliar applications of organophosphate insecticides irrespective of the
presence of flies (Liburd et al., 1998).

As organophosphates are slowly phased out by Food Quality Protection Act
(FQPA) regulations, a serious need arises for integration of multiple fruit fly control
tactics in Michigan cherry production. The FQPA (1996) amends the Federal Insecticide,
Fungicide, and Rodenticide Act (F IFRA) and the Federal Food, Drug, and Cosmetic Act
(FF DCA). It alters the guidelines by which the Environmental Protection Agency (EPA)

registers and regulates pesticide usage in the United States. This is accomplished by

56

mandating a health-based standard for essentially all foods. The standard is based on
collective exposure to dietary and worker residue concerns. Moreover, it considers the
effects of exposure to pesticides with common mechanisms of toxicity and demands a
thorough screening for probable endocrine effects, especially when used on foods
consumed by infants and children. Apples, peaches, pears and grapes are focal points for
F QPA. Consequentially, EPA is re-registering and eliminating a significant number of
pesticides under the requirements of FQPA. It has focused on organophosphates (OP)
and carbamates (CB). These chemistries are traditionally used for fruit fly control in
Michigan orchard systems. The potential restrictions are particularly important in
relation to the zero tolerance for fruit flies associated with cherry marketing. There is
currently a lack of alternative insecticides that are efficacious against this pest.
Integration of reduced-risk insecticide alternatives is crucial for a successfirl
transition from current practices to the F QPA era. New insecticide cherrristries are
generally weak contact poisons. They produce, however, an array of sub-lethal effects
such as oviposition deterrence. Neonicotinoids are an example of a new class of
insecticides. With these materials, timing of the first cover spray is critical. It must
coincide with cherry fruit fly egg-laying activities. Historically, growers have used
yellow Pherocon AM board (Great Lakes IPM, Vestaburg, MI) to detect when the first
fruit fly emerges. They make their first spray within a week of the trap catch (Prokopy
1975, Reissig 1976). Recent evidence, however, suggests that the three-dimensional
Rebell” trap (Swiss Federal Research Station, Wadswill, Switzerland) is significantly

more efficient in detecting the initial flight of the cherry fruit fly following emergence

57

(Liburd etal., 2001, Kostarides and Liburd in press). This trap caught more flies
throughout the growing season, but also detected flies 1-2 wks earlier than the Pherocon
AM board.

In an effort to reduce pesticide deposition into our environment, alternative
methods of cherry fi'uit fly suppression are being researched. Recent studies have
investigated the development of fruit-mimicking insecticide-treated spheres. These may
be used as part of IPM programs. This could provide a potential alternative to broad-
spectrum insecticide use for control of key Rhagoletis species. Laboratory and field
studies have shown that significantly more of Rhagoletis sibling species, apple R.
pomonella (Walsh) and blueberry, R. mendax Curran, maggot flies were killed with red
and green biodegradable spheres treated with the insecticide imidacloprid (Merit® 75 WP,
Bayer) compared with untreated controls (Hu et al., 1998, Liburd et al., 1999, Stelinski
et al., 2001). Mortality occurs after flies land on a trap and consume a lethal dose of the
insecticide (Stelinski et al., 2001). In addition, season-long residual activity studies
indicate a fly mortality rate of 80% fi'om spheres treated with imidacloprid at a rate of
1.5% a.i. (Hu et al., 1998). Despite their effectiveness, there have been problems with
biodegradable insecticide-treated spheres. These include fungal grth on the traps and
loss of mass due to rodent feeding. Consequently, our research is designed to test new
prototypes of these biodegradable traps.

Several advantages may be achieved fiom using biodegradable pesticide-treated
sphere technology. They include season-long monitoring and the potential to control
fi'uit flies with a single sphere deployment tactic. This requires less labor compared with

other control devices and monitoring systems. There is also a reduced risk of insecticide

58

residues in fruit. Studies conducted during the 1999 field season showed that placing
spheres at a distance 10 In around the perimeter of blueberry bushes was effective in
intercepting immigrants (R. mendax) moving into blueberry plantings (Stelinski and
Liburd 2001). Fields with a residential fly population, however, experienced higher
levels of maggot injury. The integration of perimeter biodegradable-treated trapping
devices used in concert with entomopathogenic nematodes (applied within orchards with
residential maggot population) may help to suppress cherry fruit flies and reduce maggot
injury.

Entomopathogenic nematodes are roundworrns associated with a bacterium able
to parasite and kill a large number of insects. These beneficial nematodes are
microscopic, non-segmented worms that are associated with a bacterium able to
parasitize and kill a large number of insects that occur naturally in soil all around the
world. Insect-parasitic nematodes possessing an optimal balance of biological attributes
are entomopathogenic nematodes in the genera Steinemema and Heterorhabditis.
Entomopathogenic nematodes are extraordinarily lethal to many important soil insect
pests, yet are safe for non-target organisms. This high degree of safety means that unlike
most chemical pesticides, nematode applications do not require extensive safety
equipment; and re-entry intervals, residues, contamination and pollinators are not issues.
A copiousness variety of different insect pests are susceptible to infection, yet no adverse
effects have been demonstrated against non-targets in field conducted studies (Georgis et
al. 1991 ).

Once nematodes are released, they seek out host insects and enter their prey

through body openings and emit an endo-toxin that results in death of the host insect

59

within 48 hours. The nematodes reproduce and their offspring feed on the insect cadaver
and may emerge to seek out new hosts. Thus, entomopathogenic nematodes are
nematode-bacterium complexes. The nematode may appear as little more than a
biological syringe for its bacterial partner, yet the relationship between these organisms is
one of classical mutualism. Nematode grth and reproduction depend upon conditions
established in the host cadaver by the bacterium. The bacteria (Xenorhabdus sp.for
Steinemematids, and Photorhabdus sp. for Heterorhabditids) further contributes anti-
immune proteins to assist the nematode in overcoming host defenses and anti-microbials
that suppresses colonization of the cadaver by competing secondary invaders.
Conversely, the bacterium lacks invasive powers and is dependent upon the nematode to
locate and penetrate suitable hosts.

Studies on Tephritids have demonstrated the potential for control with
entomopathogenic nematodes (Beavers and Calkins 1984, Lindegren 1990). Finney
(1983) found nematodes to be potential controls for Rhagoletis spp., and improvements in
nematode strains, production, and storage should make nematodes an even more viable
control option for cherry fruit flies. An appropriate soil environment is necessary for
effective use of entomopathogenic nematodes (Smitley et al., 1992). Application
technologies for effective use of entomopathogenic nematodes in orchards have recently
been developed. The use of entomopathogenic nematodes will specifically control larval
and pupal population thereby reduce infestation in fields. Perimeter trapping not only
enhances the nematode control strategy, but also prevents immigrants from entering the

orchard. The net effect is a set of pest management tools for control of cherry fi'uit flies.

60

 

The goal of this project was to test the efficacy of perimeter-oriented control
techniques and residential population control techniques together for a comprehensive
fi'uit fly management program.

The objectives of this study were to: 1) evaluate the effectiveness of
biodegradable pesticide-treated trapping devices against the two key species of cherry
fi'uit flies; 2) develop and compare an insecticide treated trap modeled after the Rebellm
trap to be used as a control device for cherry fruit flies; 3) preform a chemical analysis to
determine the fate of the insecticide on the modeled Rebell” trap; 4) investigate the
potential of using entomopathogenic nematodes for larval and pupal control through

laboratory bioassays.

61

MATERIALS AND METHODS

Field experiments were conducted at th e Northwest Horticultural Research
Station located in Leelanau County, Michigan. No insecticide sprays were applied to
cherry blocks during experimentation.The experimental design was a completely

randomized block with five replicates.

Biodegradable Pesticide-Treated Sphere Experiment. 2000. Field experiments were
used to determine the effectiveness of biodegradable spheres treated with a novel
neonicotinoid insecticide imidacloprid [Provado® 1.6 F (17.4% v/v a.i.; Bayer, Kansas
City, Missouri)]. Spheres were commercially prepared with the specifications described
by Liburd et al., (1999). Essentially, spheres consisted of a mixture of water (150 g),
table sugar (360 g), high fructose corn syrup (330 g), pregelatinized corn flour, (630 g),
cayenne pepper (14.7 g), and sorbic acid (1.5 g). The spheres are designed to be both
biodegradable and unattractive to wildlife. Prior to field deployment, spheres were
primarily brush-painted with a base coat of fluorescent yellow paint. The second coat
applied to the spheres consisted of 13 ml Provado® 1.6 F and 100 ml paint. The last
(tertiary) coat applied to spheres was 13 ml Provado® 1.6 F, 80 ml paint, and 20 m1
sucrose solution (fly feeding stimulant). The latex paint acts as a residue-extending agent
for the insecticide and creates a barrier to control the release of both sugar and insecticide
(Uh et al., 1998).

Two treatments were evaluated. The traps were placed approximately 20 m apart
within trees and 20 m between blocks. Treatment 1 consisted of a biodegradable sphere

treated with the insecticide Provado® 1.6 at 2% a.i. and placed within the canopy of

62

cherry trees. Treatment 2 had an identical biodegradable sphere without the insecticide
imidacloprid. Both spheres were baited with a polyethylene vial containing 5.0 grams of

ammonium acetate (Liburd et al., 1999).

Modified Pesticide RebellTM Trap Experiment. 2001. Four treatments were evaluated.
The traps were placed approximately 20 m apart within trees and 20 m between blocks.
Treatments were as follows: 1) pesticide-treated wooden Rebellm trap; 2) pesticide-
treated biodegradable sphere; 3) untreated wooden Rebell" trap (control); 4) untreated
biodegradable sphere (control). Wooden Rebell” trap dimensions were the same as the
commercially available plastic monitoring Rebellm trap. Wooden Rebellm were first
prepped brush painted with 200 ml “Karo” corn syrup mixed with lqt of Glidden grey
primer (Cleveland, Ohio). Two coats were applied.

Modified wooden Rebell” traps were then treated with imidacloprid at a rate of
4% a.i.. The pesticide-treated biodegradable spheres were prepared as previously
discussed for the biodegradable pesticide-treated sphere experiment in 2000. The 4% a.i.
insecticide-treated traps were prepared as follows: traps were primarily brush-painted
with a base coat of fluorescent yellow paint alone. The second coat applied to the traps
consisted of 26 ml imidacloprid and 87 ml paint. The last (tertiary) coat applied to
spheres was 26 ml imidacloprid, 67 ml paint, and 20 ml sucrose solution. Treatments 3
and 4 (untreated controls) were a modified wooden Rebell". trap and biodegradable

sphere, respectively, with no insecticide incorporated into the paint mixture.

63

Monitoring. Both traps and plexiglas panes was checked twice per week and the number

of cherry fruit flies were counted, sexed, and removed.

Statistical Analysis. Data from biodegradable trapping device experiments were
anaylzed by AN OVA followed by mean separation using the least significant difference

test (LSD) test (SAS Institute 1989).

Entomopathogenic Nematode Bioassays. 2000. This study was conducted to
determine the susceptibility of mature third instar larvae of R. cingulata to five species of
entomopathogentic nematodes: Steinernema feltiae (Filipjev), S. carpocapasae (Weiser),
S. riobravis (Cabanillas, Poinar, and Raulston), Heterorhabditis bacteriophora (Poinar),
and H. marelatus (Liu and Berry).

Third instar larvae were obtained after emerging from field-collected unsprayed
cherries. Infested cherries were placed on a wire screen and emerging larvae collected
into a plastic pan with distilled water. Once removed from the water, larvae become
active and pupated. Fruit fly larvae were exposed to an equivalent of a 106/m2
concentration of infective juvenile nematodes in petri plates (100 x 15 mm) lined with
9.0-cm-diameter F isherbrand (P5) filter paper. Twenty larvae were selected randomly for
each replicate plate. Distilled water (0.2 ml) was pipetted into all petri plates to moisten
the filter paper. One milliliter of the appropriate nematode suspension (6360 infective
juveniles/ml) was then added to each dish. Depending on availability of larvae, three to
four replicate plates were used for each nematode species and the controls. Bioassays

were repeated on two separate dates.

64

Due to the variability in availability of fruit fly larvae, the number of replicates
was different for the two experiments. A distilled water control and four dishes per
nematode species were used in Experiment 1. By the third week of July, when the
second experiment was conducted, the availability of R. cingulata was limited. In the
second experiment,

H. bacteriophora was not assayed and only three dishes per nematode species and control
were used. Because pupation began soon after adding larvae to plates, an effort was
made to select larvae in which pupation had not yet begun. Larvae which displayed
distinctive mouth hooks, no brownish pigmentation, and no other signs of pupation were
preferentially selected.

After addition of infective entomopathogenic juveniles, the petri dishes were
covered, sealed with strips of parafilrn, and incubated at 25°C. After 24 hours, the Petri
dishes were unsealed and dry vermiculite was sprinkled overthe pupae. The closed
dishes were maintained at the same temperature and 55-60 % relative humidity for 7
days. Then 10 puparia were collected at random from each dish and dissected to
determine pupal mortality and the presence of nematodes.

Living pupae were whitish-yellow with developing wing buds, wings, and legs.
A distinct head, compound eyes, thorax, and abdomen were easily distinguished. Tissues
of parasitized pupae were yellow-brown and contained infective juveniles and adult
nematodes. Pupae were considered very little tissues, were yellow-brown without
distinctive segmentation, or shriveled with remaining tissues fibrous. A visible tracheal

system through the puparial shell indicated that the larva was infected by the nematodes

65

Statistical Analysis. Percentage mortality data of R. cingulata pupae were analyzed after
square root arcsine transformation. Analysis and comparison of mortality data were done
using AN OVA (General Linear Model procedure, SAS, 1996) followed by Least

Significant Difference (LSD) test.

Pesticide Residual Analysis. This experiment was conducted to determine whether the
concentration of insecticide used in wooden Rebell traps changed over the course of the
growing season. Determination of total residues of the insecticide imidacloprid from
pesticide-treated biodegradable spheres was done with extraction with an acidic aqueous
solvent. The extract was filtered through a Celite vacuum filter flask and hydrophobic
interferences were washed with hexane. The aqueous portion was retained and put onto a
XAD4 cleanup column. The residues were eluted off the XAD4 column with methanol
and oxidized to 6-chloronicotinic acid with potassium permanganate. Finally, the extract

was analyzed with GC/MS.

Statistical Analysis. Data were subjected to analysis of variance (AN OVA) followed by

Least Significant Difference (LSD) test.

66

RESULTS

Biodegradable Pesticide -Treated Trapping Devices. In the experiments to
investigate the efficacy of biodegradable pesticide—treated spheres, significantly more R.
cingulata were captured on traps with 2% a.i. compared with untreated spheres.
Transparent plexiglas panes placed beneath treated spheres captured six times as many R.
cingulata as the unbaited biodegradable traps (Fig. 11).

During the 2001 growing season, significantly (F = 210.97; df = 3,6; P < 0.0001)
more R. cingulata were captured on wooden Rebell“ traps treated with 4% imidacloprid
than any other traps tested (Fig. 12). Pesticide-treated wooden Rebell“ traps caught 6.8,
5.9, 2.0 times as many R. cingulata as the biodegradable pesticide-treated sphere,
untreated wooden Rebell” trap, and untreated biodegradable sphere. The biodegradable
pesticide-treated sphere caught significantly more R. cingulata than both untreated traps

(Fig. 12).

Entomopathogenic Nematode Bioassays. 2000. In Experiment 1, infestations of
infective juveniles of S. carpocapsae and S. feltiae caused significantly higher pupal
mortality in R. cingulata than did S. riobravis (Table 3). Sixty-five percent of the
recently formed pupae were dead and contained S. carpocapsae juveniles.

Relative to the other four species, a greater number of S. carpocapsae infective
juveniles entered the R. cingulata larvae, and juveniles were recorded in 31 of 40 pupae.

Thirteen puparia each contained hundreds of S. carpocapsae infective juveniles.

67

Heterorhabditis bacteriophora killed a greater percentage of pupae then S.
feltiae. Seven puparia were infected with H. bacteriophora and eight puparia with S.
feltiae. Seven puparia of each species were infected with hundreds of infective juveniles.
A greater percentage (50%) of pupae was dead but not infected with S. feltiae. Higher
mortality of non-infected pupae may have been due to an interruption of metamorphosis.

Even though larval selection was randomized in Experiment 2, a higher mortality
(43.3%) in the controls was observed. This may have been due to their collection later in
the season, when lower numbers per cherry were found. Earlier in the season, adequate
numbers of larvae were collected within a few hours of holding the cherries over water-
filled trays. Later in the season it was necessary to hold cherries for up to 24 hours
before adequate numbers of larvae could be obtained. Depending on when the larvae
emerged from the cherries, they could have remained in water from 1 to 24 hours.

In the second experiment, larvae were also significantly more susceptible to
infective juveniles of S. carpocapsae and S. feltiae than to S. riobravis (Table 3).
Steinermena carpocapsae juveniles were found in 16 of 30 puparia, and 7 contained
hundreds of infective juveniles. Ten of 30 puparia had S. feltiae juveniles and 11 puparia
contained hundreds of juveniles. Sixty percent of the dead pupae had an S. feltiae
infestation

(Table 3).

68

DISCUSSION

Biodegradable Trapping Devices. This study demonstrated that baited biodegradable
trapping devices treated with the insecticide imidacloprid were more effective in killing
cherry fruit flies than identical untreated devices. Specifically, baited biodegradable
wooden Rebell“ traps treated with 4.0 % a.i. imidacloprid killed significantly more flies
than all other traps tested.

These results show the potential for reduction of unnecessary spray depositions
into our natural resources. Through improving upon trapping systems, we believe this
will help facilitate the transition from conventional to alternative control technologies in

Michigan fruit production systems.

Entomopathogenic Nematodes. Steinernema carpocapsae, because of their small size,
may have infested more R. cingulata larvae than other species. This ambusher nematode
is also active against other dipterans and had been adapted to infect insects at the soil-
litter interface (Kaya and Gaugler 1993). When these nematodes are present in the soil,
R. cingulata larvae could become infected as they drop onto the ground.

The use of entomopathogenic nematodes is really still in its infancy and there is
considerable potential yet to be fulfilled (Bedding 1999). New species and strains of
entomopathogenic nematodes are constantly being found and can now be stored in liquid
nitrogen indefinitely to preserve genetic diversity (Popiel and Vasquez, 1991 Curran et
al., 1992). Most of our domestic animals and plants have been modified by artificial

selection and this is undoubtedly possible with entomopathogenic nematodes

69

(particularly because their short life cycle) and has indeed been already attempted with
some success. As better and better strains become available more kinds of insect pests
can be targeted and fewer entomopathogenic nematodes will be required for treatments
that will therefore become less expensive. There is also much research being conducted
on methods for applying entomopathogenic nematodes that should help to firrther reduce
treatment costs. However, in the end using entomopathogenic nematodes to control
insects in orchard systems may be partly up to the ingenuity of the grower to find out the

best possible means of and timing for applying them for their particular situation.

70

Table 3. Mortality of Rhagoletis cingulata pupae after exposure as larvae to 10°/m2

concentration of infective juveniles of five species of entomopathogenic nematodes.

 

 

Pupal Nematode Recovery

Mortality Infected (%)
Experiment 1
S. carpocapsae 72.5 :1: 1.27 a 65.0 i 1.32 a
S. feltiae 70.0 :t 0.38 a 35.0 i 0.50 be
H. bactiophora 62.5 :1: 0.79 ab 50.0 :1: 0.41 ab
H. marelatus 55.0 i 0.59 ab 15.0 i 0.65 c
S. riobravis 40.0 :b 0.57 be 17.5 i 0.75 c
Control 22.5 d: 0.25 c 0.0 d
Experiment 2
S. carpocapsae 83.3 i 1.89 a 83.3 :1: 0.67 a
S. feltiae 73.3 i 1.26 a 60.0 :1: 1.53 ab
H. marelatus 60.0 i 0.93 ab 26.7 at 1.45 be
S. riobravis 40.0 i 0.73 b 23.3 i 1.33 bc
Control 43.3 i 0.33 b 0.0 c

 

 

Means within same column followed by the same letter are not significantly different
(P 5 0.05; LSD test).

71

Mean # of Flies I Trap

 

 

 

 

 

 

 

 

b

 

 

 

 

_l..__

 

Traded Sphere

Fig. 11. Captures of Rhagoletis cingulata from 11-30 July captured on plexigals

Urtreaedsmene

pans beneath biodegradable pesticide-treated (2% a.i. imidacloprid) spheres,

Leelanau County, Michigan (2000).

72

 

350

40)

 

300

 

N

0"

o
I

 

N

O

O
l

   

 

Mean no. flies Itrap
8

 

A

O

o
I

 

(’1
O
I

 

       

 

 

O
r

4% Wooden Rebell' 4% Biodegradable' Wooden Rebell Biodegradable
Sphere (control) Sphere (control)

Fig.12. Captures of Rhagoletis cingulata from 1 July — 25 Aug. on
plexiglas panels beneath biodegradable trapping devices, Leelanau
County, Michigan (2001).

* 4% a.i. imidacloprid. (F = 210.97; df= 3.6; P < 0-0001)

73

 

SUMMARY AND CONCLUSIONS

Both visual (yellow color) and olfactory (ammonium baits) stimuli are important
in the orientation of R. cingulata to Rebell“ traps. Therefore, I recommend that traps can
be baited with ammonium compounds in order to effectively monitor for the eastern
cherry fruit fly. In contrast, the visual stimuli appear to play a major role in the
orientation of R. fausta to RebellTM traps. Baiting traps with ammonium compounds,
therefore, is not necessary. F urtherrnore, host resources that include fruit load and foliage
affect the number of Rebellm traps needed per hectare to effectively monitor cherry fruit
fly populations.

The results from the evaluation of reduced-risk insecticides showed potential for
future use of neonicotinoid chemistries in cherry fruit fly control. Fruit infestation levels
indicated that these compounds were equally effective as conventional control methods in
managing cherry fi'uit flies. Unlike organophosphates, the mode of action for
neonicotinoids is host specific, thus not posing a threat to non-target organisms.

Biodegradable trapping devices treated with imidacloprid (Provado 1.6 F ®) were
effective in killing cherry fruit flies. Specifically, modifications of RebellTM traps treated
with 4% a.i. were highly attractive in luring adults to its surface and killing the flies.
Based on these findings, I highly recommend deploying modified Rebellm traps for both
fly control and as a way to reduce pesticide deposition into the environment. To further
decrease the number of insecticide applications needed in cherry orchards to suppress fly

populations, entomopathogenic nematodes may have a role. Of the five species

74

evaluated, Steinernema carpocapsae, provided the best efficacy. Athough further
research is advised for cost-effective application of entomopathogenic nematodes,
laboratory assays have shown potential for their integration into a pest management
system.

Overall, this research confirmed potential for use of RebellTM traps for detecting
the primary flight of residential fly populations. Upon emergence, it is advisable to
deploy modified pesticide-treated (4% a.i. Provado® 1.6 F) Rebell“ traps to attract and
kill cherry fruit flies. To further suppress pest populations, applying entomopathogenic
nematodes to target fly larvae is an alternative to conventional sprays. The ability to
develop a successful IPM program and minimize environmental risk that addresses the

complexity of tropic interactions in agricultural systems holds the key to the future.

75

 

 

 

APPENDIX

76

APPENDIX 1
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.: 2002-03

Title of thesis or dissertation (or other research projects):

Integrated Management Strategies For Control Of Cherry Fruit Flies, Rhagoletis cingulata and
Rhagoletis fausta (Diptera: Tephritidae)

Museum(s) where deposited and abbreviations for table on following sheets:

Entomology Museum, Michigan State University (MSU)

Other Museums:

lnvestigator’s Name(s) (typed)
Jessica Lynn Kostarides

 

 

Date 05/03/02

*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.

77

 

Appendix 1

Table 4: Voucher specimen data

Page_1_of_]_Pages

 

 

 

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montflmox :53 83mm...

883 Essa: {28:83.
3.3800: a £02m .2368 $3

 

 

 

 

 

 

 

 

 

 

 

 

 

2m: 2 2
2220 E20 :3 8:852
.00 80 25.10.: age 888%
3m: 2 2
3m: 52.3 .5: .82, 552
.8 3828.. 36.5.2 ensues REESE
m M «O 0+ 8
u are .m r m m e .m. e cosmoaou new
m .m m. m w w m m. m w now: .0 882.8 2950on .6. Son .33 :95 850 8 $3on
M w m o A A P N m E
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78

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79

 

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85

 

 

  

   

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