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This is to certify that the

thesis entitled

ECOLOGY OF THE COLORADO POTATO BEETLE,
Leptinotarsa decemlineata (SAY), ON HORSENETTLE,
Solanum carolinense L., IN MICHIGAN

I presented by

Jaime Mena-Covarrubias

has been accepted towards fulfillment
of the requirements for

M . S . degree in Entomology

 

 

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Major professof

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ECOLOGY OF THE COLORADO POTATO BEETLE. Leptinotarsa decantineata (SAY).
ON HOW Solarium wolinense L.,
IN MICHIGAN.

By

Jaime Menu-Cannabis:

A THESIS

Submitted to
Michigan State University
in partial fulfillment of the requirements
for the degree of

MASTER OF SCMCE

Department of Entomology

I 4

:2 b I“.

ABSTRACT

ECOIDGY OF THE COIDRADO POTATO BEETLE. Leptitwtarsa decantineata (Say) .
ON HORSENETTLE. Solarium carolinense L. .
IN MICHIGAN.

By
Jaime Menn-Covnrruhiu

Population dynamics of Colorado potato beetle (CPB), Leptinotarsa decemlineata (Say)
on horsenettle was determined through field experiments. Development rate and
survival on two host plants was evaluated in a laboratory study. The optimum sample
size for studying CPB on horsenettle is calculated. A technique for estimate an error
term for Southwood's stage-specific mortality is presented. Accumulated mortality for
CPB egg and larvae stages was higher than 90%. Predators with chewing mouthparts
were more abundant early in the season. and predators with sucking mouthparts late in
the season.There were no differences in development rate, pupal weight or survival for
two beetle populations on potato or horsenettle foliage. CPB has been very selective for
laying its eggs on horsenettle. The CPB has been able to feed efficiently on horsenettle
plants while keeping its ability to exploit potato plants. but a probable difl'erence in

oviposition behavior is developing.

ACUOWLEDGMENTS

Many people have supported and encouraged my education and research
endeavors. I wish to express my thanks and gratitude to all of those who helped me.

I extend the most sincere appreciation to my former advisor, Dr. Frank
Drummond for his inspiration. constant aid. guidance and encouragement throughout
the course of graduate study and in the preparation of this thesis. In addition to
exhibiting the utmost patience with me throughout this endeavor. his lofty quality as a
teacher. researcher and friend will be always remembered with pride.

I would like to express my greatest thanks to Dr. Dean Haynes, who has spent his
invaluable time and energy in guiding me writing this thesis. I am deeply indebted for
his unfailing interest. assistance and valuable help as an advisor the last two months
of my student days at Michigan State University (MSU).

Appreciation is extended to Drs. George Bird. Stuart Gage and Ed Grafius.
members of my graduate comittee. Through their support. I have been afforded the
opportunity to gain invaluable experience while completing this thesis.

The author also wishes to extend his appreciation to the Instituto Nacional de
Investigaciones Pecuarias Agricolas y Forestales (INIFAP) for its financial support and
allowing the author to pursue his studies here. To Dr. Ramon Martinez Parra I owe an
immense debt of gratitude for his invaluable help and support to overcome many of the

bureaucratic problems found on the way.

iii

Thanks to my fellow graduate students who were so instrumental in the
education I received during my study at MSU, particularly David Cappaert. a friend who
never doubted and who supplied needed encouragment.

This thesis could not be completed without the help of my friends Abelardo and
Liliana. They shared their appartrnent with me regardless of sacrificing their privacy.
Their friendship and mexican warmth made of my last five weeks in Michigan. an
enjoyable experience.

I have no words to express my gratitude to my parents who have always prayed
for me. and paved the way for my education.

Finally and most of all. to my wife Teresa. who never waivered in her total
support of my effort. . . . during what must have seemed like an endless period of time.
Without her love. faith and sacrifice. this effort would have been difficult to achieve. To
my two little sweethearts. Julian and Martha. who had to share their father with this

endeavour.

iv

TABLE OF CONTENTS

P380
LIST OF TABLES vii
LIST OF FIGURES ix
INTRODUCTION 1
LITERATURE REVIEW 3
CPB HOST FINDING 4
CPB HOST MON BEHAVIOR 6
CPB HOST PLANT MON FOR OVIPOSITION 7
DIAPAUSE 8
HOST PLANT RESISTANCE 9
NATURAL ENEMIES 12
HOME 13
MANUSCRIPT I. DEVELOPMENT AND SURVIVAL 01" TWO POPULATIONS
OF COLORADO POTATO mm (OOLEOPTERA: WM) ON
HOW Solanum carolinense L. 15
ABSTRACT 16
lNTRODUCTION 17
MATERIALS AND METHODS 18
Site description 18
Stage-specific survival . 19

Field sampling 20

Cohort study
Development rate
Beetle sampling
Horsenettle sampling
OONCHJSIONS
ACKNOWLEDGMENTS
REM CITED
APPENDIX . THE JACKNII'E APPROACH TO VARIANCE ESTIMATION FOR
SOUTHWOOD‘S STAGDSPECIFIC MORTALITY
ABSTRACT
INTRODUCTION
MATERIALS AND METHODS
RESULTS AND DISCUSSION

LITERATURE CITED

BIBLIOGRAPHY

vi

20

21

25

25

27

29

35

37

39

67

72

73

74

76

85
87

LIST OI" TABLES

MANUSCRIPTI

Table 1 . Southwood's stage-specific mortality for the Colorado potato
beetle on horsenettle at Kellog Biological Station. Hickory
Corners. MI .

Table 2. Changes in the Colorado potato beetle egg mass size on
horsenettle at the Kellogg Biological Station. Hickory Corners.
MI in 1988.

Table 3. Egg mass distribution on difl'erent plants from a Colorado
potato beetle population adapted to horsenettle at Kellogg
Biological Station. Hickory Corners MI in 1988.

Table 4. Larvae development and pupae weight of two population of
Colorado potato beetle on potato and horsenettle plants in 1988.

Table 5. Survival of two populations of the Colorado potato beetle fed on
two difl'erent host plants under laboratory conditions in 1988.

Table 6. Larvae development and pupae weight of a Colorado potato
beetle populationon on two different foliage conditions on
horsenettle plants in 1988.

Table 7a. Mean. variance and standard errors of the difi'erent stages of
the Colorado potato beetle on horsenettle during the summer of
1987. Weed field .

Table 7b. Mean. variance and standard errors of the different stages of
the Colorado potato beetle on horsenettle during the summer of
1987. Corn field.

Table 7c. Mean, variance and standard errors of the difl‘erent stages of
the Colorado potato beetle on horsenettle during the summer of
1987. Grass Field.

Table 8. Mean. variance and standard errors of the difl'erent stages of
the Colorado potato beetle on horsenettle during the 1988
sampling in the Corn field.

Table 9. Spatial pattern analysis of the Colorado potato beetle on
horsenettle in 1987. based on Taylor's power law regression.

Table 10. Spatial pattern analysis of the Colorado potato beetle on
horsenettle in 1987 and 1988 based on Taylor's power law

vii

41

42

45

47

49

52

regression.
APPENDIX

Table 1 1. Number of individuals entering each stage estimated with
Southwood's method for estimate stage-specific mortality in
Colorado potato beetle on horsenettle in 1987.

Table 12. Number of individuals entering each stage estimated with
Southwood's method for estimate stage-specific mortality in
Colorado potato beetle on horsenettle in 1988.

Table 13. Stage-specific mortality estimates for the Colorado potato
beetle on horsenettle in 1987. calculated with the Jacknife
technique.

Table 14. Stage-specific mortality estimates for the Colorado potato
beetle on horsenettle in 1988. calculated with the Jacknife
technique.

Table 15. Comparison between the common and the Jacknife estimate
of the stage-specific mortality rate using Southwood's method.

viii

79

81

82

LIST OI" FIGURES

MANUSCRIPT I

Figure 1 . Horsenettle density of three difl'erent fields at the Kellogg
Biological Station during 1987. DD 10 measurements beginning
on May 26.

Figure 2. Relationship between horsenettle stem density and sampling
date in the Corn field at the Kellogg Biological Station in 1988.
DD 10 measurements started on May 22.

Figure 3. Population density of Colorado potato beetle adults on
horsenettle at the Kellogg Biological Station in 1987. DD 10
accumulation started on May 26.

Figure 4a. Population density of Colorado potato beetle eggs on
horsenettle at the Kellogg Biological Station in 1987. Weed Field.
DD 10 measurements starting on May 26.

Figure 4b. Population density of the Colorado potato beetle eggs on
horsenettle at the Kellogg Biological Station in 1987. Corn Field.
DD 10 accumulation started on May 26.

Figure 4c. Population density of the Colorado potato beetle eggs on

horsenettle at the Kellogg Biological Station in 1987. Grass Field.

DD 10 accumulation started on May 26.

Figure 5a. Population density of Colorado potato beetle larvae on
horsenettle at the Kellogg Biological Station in 1987. Weed Field.
DD 10 measurements beginning on May 26.

Figure 5b. Population density of Colorado potato beetle larvae on

horsenettle at the Kellogg Biological Station in 1987. Corn Field.

DD 10 accumulation started on May 26.

Figure 5c. Population density of Colorado potato beetle larvae on

horsenettle at the Kellogg Biological Station in 1987. Grass Field.

DD 10 accumulation started on May 26.

Figure 6a. Population density of Colorado potato beetle natural enemies
onhorsenettle at the Kellogg Biological Station in 1987. Weed
Field. DD 10 measurements beginning on May 26.

Figure 6b. Population density of Colorado potato beetle natural enemies
on horsenettle at the Kellogg Biological Station in 1987. Corn

1X

55

55

57

57

Field. DD 10 accumulation started on May 26.

Figure 6c. Population density of Colorado potato beetle natural enemies
on horsenettle at the Kellogg Biological Station in 1987. Grass
Field. DD 10 accumulation started on May 26.

Figure 7. Egg masses preyed upon by Colorado potato beetle predators
on horsenettle at the Kellogg Biological Station in 1987. DD 10

accumulation started on May 26.

Figure 8. Population density of Colorado potato beetle adults on
horsenettle at the Kellogg Biological Station in 1988. DD 10
measurements beginning on May 22.

Figure 9. Population density of Colorado potato beetle eggs on
horsenettle at the Kellogg Biological Station in 1988. DD 10
accumulation started on May 22.

Figure 10. Population density of the Colorado potato beetle larvae on
horsenettle at the Kellogg Biological Station in 1988. DD 10
accumulation started on May 22.

Figure l 1 . Population density of Colorado potato beetle natural enemies
onhorsenettle at the Kellogg Biological Station in 1988. DD 10

accumulation started on May 22.

Figure 12. CPB egg density on horsenettle as obtained from sampling an
area of 130 m2.

Figure 13. Relationship between horsenettle size and sampling date at
the Kellogg Biological Station in 1988.

Figure 14. Estimation based on two sampling methods on the percentage
of egg masses preyed upon by Colorado potato beetle predators on
horsenettle at the Kellogg Biological Station in 1988.

Figure 15. Colorado potato beetle egg mortality distribution in relation
to the egg mass age on horsenettle at the Kellogg Biological
Station in 1988.

Figure 16a. Sample size needed to estimate Colorado potato beetle adult
density on horsenettle.

Figure 16b. Sample size needed to estimate Colorado potato beetle egg
mass density on horsenettle.

Figure 16c. Sample size needed to estimate Colorado potato beetle larvae
density on horsenettle.

Figure 17. Sample size needed to estimate horsenettle density based on
number of stems per m2.

APPENDIX
Figure 18. Relationship between the size of the subsample removed and

the variability of the sampling data of the Colorado potato beetle
on horsenettle.

59

59

61

61

62

INTRODUCTION

The Colorado potato beetle (CPB). Leptinotarsa decemlineata (Say) is one of the
most important pests of potatoes in many regions of the United States. Canada. Europe.
USSR. and Turkey (de Wilde and Hsiao 1981). The genetic variability of the insect along
with the mismanagement that have characterized commercial potato areas during the
last 100 years. have made of this insect one of the best known cases in the
entomological literature. The first commercial insecticide sprayers were developed for
control this insect in the 1870's (Casagrande 1987). CPB is also a classical case for
explaining the potential of an insect to develop resistance to insecticides. After its
introduction in Europe. CPB forced the creation of an organization for dealing with this
insect exclusively. However. the CPB was an unknown insect to the entomologists
before 1800. When Thomas Say collected the specimens for the description of the
species. he reported it as a rare insect feeding on buffalo burr Solanum rosiratum . on
the hills of the Rocky Mountains. It took about 40 years of exposure to potato plants
before the beetle become one of the most destructive insects in agriculture (Casagrande
1985).

The CPB probably evolved in southern Mexico, feeding upon 8. rostratum
(Tower 1906) a weed common to disturbed areas of North America and also native to
Mexico (Whalen 1979). Host and beetle dispersed northward. invading the eastern
slopes of the Rocky mountains (Casagrande 1985. 1987). In this habitat. CPB also feeds
on S. elaeagnifolium (Hsiao 1986). Beetles. intraspeciflc variation in response to host

species has been noted for geographically widely separated populations (Hsiao 1978.

6

1981. de Wilde and Hsiao 1981. Hare and Kennedy 1986). Populations from Europe.
parts of Asia, and North America vary in growth and survival on difl‘erent host plants.
Shifts to feeding on closely related hosts of the pest may not require major genetic
changes in physiology or behavior (Tabashnik 1983). specially if the genetic make up of
the population includes some sort of "all purpose" genotype having high fitness
simultaneously on several host species (Mitter and Futuyama 1983). The host shift of
the CPB from S. rostratum to S. tuberosum probably occurred without major changes
in physiology or behavior (Hsiao 1978. Horton et al 1988).

At the Michigan State University Kellog Biological Station (KBS) at Hickory
Corners. MI. a population exist that fed on potatoes before 1954, but since then.
horsenettle has been the host plant for the beetles. I investigated the population
dynamics of KBS beetles as well as its natural enemies on horsenettle. its new host for
the last 34 years. Additionally. the possible difl'erences in host plant use between the
KBS population and a CPB population that has been feeding on potatoes (Montcalm
population) were evaluated under laboratory conditions. The sample size needed to

study the CPB on horsenettle was also calculated.

LITERATURE REVIEW

CPB is an oligophagous beetle that feeds on members of the Solanaceae. and
primarily on plants in the genus Solanum (Hsiao 1981. 1986). Throughout Colorado.
New Mexico. Texas. Oklahoma. and Mexico. S. rostratum is the predominant host.
followed by S. elaeagnifolium . In Arizona. where S. rostratum is not prevalent. S.
elaeagnifoltum is the principal host. In several central and south eastern states. S.
caroltnense is an important native host. Several introduced or cultivated plants,
including 8. dulcamara . S. melongena . Lycopersicum esculentum . S. villosum , and
Hyoscyamus niger are minor or occasional hosts (Hsiao 1978).

Different geographic populations of CPB in North America use different local
hosts. Varying degrees of specialization in larval digestive efficiency (Hsiao 1978) and
adult food-plant preference have evolved (Harrison 1987. Harrison and Mitchell 1988.
Horton et a1 1988). The existence of a CPB population from southern Arizona that is
uniquely adapted to a native host. S. elaeagnifoltum . is reported by Hsiao (1978). Due to
the ecological conditions that limited the species of host plants available. a CPB
population was adapted to S. carolinense in North Carolina. and it is reported as an
example of host expansion rather than host shift (Hare and Kennedy 1986) . Horton et al
(1988) indicate that the success of CPB on S. sarraooides in Canada is also due to a diet
expansion by this population. This variability has a strong genetic component. and it
may be a major factor in the CPB success in colonizing new areas (Jacobson and Hsiao

1983).

CPB HOST FINDING

The first step in host plant selection is the orientation of an insect while
walking or flying (Visser and Thiery 1984). As early as 1926. Mclndoo used a Y-tube
olfactometer to demostrate attraction to unbruised potato foliage. In a series of detailed
studies. J. H. Visser and his colleagues have shown that CPB adults orient to
solanaceous plants by sensing complex blends of "green leaf volatiles" (Visser and
Nielsen 1977. Ma and Visser 1978. Visser and Ave 1978). Through olfactory
discrimination over a long range. exploration is to some extent confined to a relevant
part of the vegetation. Complexes of the general "green leaf volatiles" form a
predominant aspect of all leaf odors. discernible in the different and particular ratios
(Ma and Visser 1978. Visser and Ave 1978. Visser and de Wilde 1980). An essential part
of the "green volatiles" is a complex of C6 alcohols. aldehydes. and corresponding
derivates generally distributed in green leaves (Visser et a1 1979. Thiery and Visser
1987).

The presence of a mixture of components can be detected by the antennal
receptors. These receptors transfer information to the deutocerebrum where two classes
of neurons are present: one class containing neurons which are not very specific for the
tested compounds. and another class with highly specialized neurons (de Jong and
Visser 1988a). Their different responses suggest two channels for the processing of
olfactory information in the antennal lobe: one channel for the detection of the
presence of "green leaf odor" components. and another one for an evaluation of the
component ratios. A study of the antennal receptor responses indicates that this
mechanism is also present at the peripheral level of the CPB's nervous system (de Jong
and Visser 1988b). The presumed separation of olfactory information by these groups is
more obvious at the deutocerebral than peripheral level (dc J ong and Visser 1988b).

From some field observations on flying CPB it would seem that odor of potato

plants may have an anestant effect (de Wilde 1976). Odor-conditioned anemotaxis is

5

much more likely to be of practical significance for orientation at a distance in the field
(Kennedy 1977a, 1977b). In the field. however. wind turbulence will blend volatiles from
a mixed stand of plants (Stanton 1983, Visser 1983). It is expected therefore. that the
beetle's range of attraction to host-plant odor is reduced in mixed cropping systems.
Masking the attractive host-plant odor will then hinder the beetle's searching for host
plants (Thiery and Visser 1987). S. rostratum and many of the other Solanum hosts
occur in large patches may have eased the problems of olfaction and detection by
providing a wide and intense odor plume that would not be completely disrupted by
small-scale turbulence (May and Ahmad 1983). For the anemotactic response. the
presence of the four terminal antennal segments is essential. As 99% of the trichoid
chemoreceptors are located on these four segments (Schnatz 1953 in May and Ahmad
1983) it is intriguing to think that these sensilla have at the same time a anemoreceptor
function (May and Ahmad 1983). In western Europe. host-finding by the CPB happens
mainly while the beetle is walking (de Wilde 1979. 1981 observations in Thiery and
Visser 1987). Under field conditions. walking CPB find potato plants from a distance of
6 m when these plants were located up wind (de Wilde 1976). If potato rows were absent
or at a long distance. the tracks often bore no relation to the wind direction. but were
directed towards the nearest green vegetation (de Wilde 1976). Caprio (1987) also
indicates that olfactory and visual cues in CPB are not active over a distance of 15 m.
The capacity to perceive the food-plants exists with larvae. They are able to
locate host plants from a very short distance by smell (Chin 1950 in Hsiao 1969) and
sight (de Wilde 1958). However. the perceptive ability of the larvae is limited to a
distance of less than 5 cm (Hsiao 1969). When larvae fall to the ground during heavy
rains or run out of food. they search in a random until guided by olfactory and optic

stimuli (Hsiao 1969, Visser and de Wilde 1980).

CPB HOST SELECTION BEHAVIOR

Prior to feeding or oviposition. many insect herbivores show stereotyped
sequences of sampling behavior (Miller and Strickler 1984) and subtle variations in
these behavior patterns can be correlated with differences in plant characteristics
(Harrison 1987). Food plant acceptance involves complex set of stimuli as well. and
beetles may be capable of discriminating among closely related Solanum species by
examining the surface of their leaves (Harrison 1987. Harrison and Mitchell 1988).
Behavioral categories with functional significance in terms of plant perception and
regulation of meal size in CPB adults are:

Examine: It is the time spent by the beetles on the leaf surface beginning with
first physical contact with the leaf and ending with transition to macerate . Active
movements include walking. palpating (repetitive contacts by maxilari palpi on the
leaf surface) and antennal waving. Sensory input may be received by sensilla located on
the antennae. maxilary palps. labial palps. and tarsi (Harrison 1987).

Macerate: A period following examine during which the leaf edge is "squeezed"
with repetitive movements of the mandibles .On acceptable host plants this piercing
action of mandibles release visible droplets of plant fluid bringing gustatory sensilla
on the beetle‘s mouth parts (Mitchell and Harrison 1984) into direct contact with leaf
saps. On plants that are not eaten, action of the mandibles is often less vigorous. and
gentle pressing of the leaf edge does not result in apparent breaks of leaf tissue.
Antennae are actively drawn towards the leaf surface during macerate . suggesting that
plant volatiles may be released (Harrison 1987).

Small bite: A bite is noted when a visible fragment of leaf is taken into the oral
cavity. Beetles typically took one or two bites before resuming feeding (Harrison 1987).

Sweep feed: Rapid feeding characterized by repetitive bites along the leaf edge.
Feeding bouts normally terminated in one or more of the following: grooming. rest or

further examination of the leaf surface (Harrison 1987).

On preferred species. beetles usually sampled and fed at a single site on the leaf
before ending the feeding bout with a long period of grooming and rest. On less-preferred
plants. fewer insects proceeded directly through the sequence. and many re-initiated
sampling and feeding at different sites on the leaf before stopping to rest or groom
(Harrison 1987). A similar pattern of time allocation on different hosts has been
described by de Wilde (1958) for larvae of the CPB. Individuals that feed on marginal
hosts sample them less prior to feeding. and selection for these feeders may establish
local populations with broader feeding preferences that are capable of exploiting novel
host plants (Harrison 1987).

CPB HOST PLANT SELECTION FOR OVIPOSITTON

Oviposition by adult females is the point at which the most important host-
selection behavior takes place. To some degree this is influenced by different stimuli
than feeding (May and Ahmad 1983). In this process. the physical characters of the
plant seem to play a .minor role. since the female lays on surfaces as diverse as hairy
and spiny leaves. glass dishes. copper screens. or paper towels (Hsiao and Fraenkel
1968). Chemical stimuli received from the plant appear to be decisive. Both positive and
negative chemical stimuli influence the selection of a plant. Thus in Capsicum annum .
egg laying never occurs (Hsiao and Fraenkel 1968). The black night shade, S. nigrum
was superior to potatoes and S. rostratum in eliciting egg laying. with twice the
percentage of eggs laid on this plant that on potato (Hsiao and Fraenkel 1968). However,
this plant does not support larval growth and it is eaten only occasionally. and the
adults rarely feed on this plant. These data indicate that acceptability and suitability of
a plant for feeding are not primarily related to the act of oviposition (Hsiao and
Fraenkel 1968). This conclusion resembles a case described by de Wilde et al (1960)
where S. luteum a toxic plant to larvae was prefered to potato for oviposition. J ermy
and Szentesi (1978) when working with the insects Acanthoscelides obtectus, Bruchus

pisorum and Pieris rapae concluded that chemoreceptors presumably located on the

8

ovipositor of the insects studied play only a subordinate role in governing egg-laying
behavior. Thus. the information on oviposition site selection is probably perceived by
chemoreceptors located on other parts of the body such as the legs and head appendages
(Jermy and Szentesi 1978). Hsiao and Fraenkel (1968). Latheef and Harcourt (1972)
demostrated that feeding conditioning does not alter the CPB oviposition preference.
Waldbauer (1962) showed that feeding on non solanaceous plants did not modify the
tabaoo hornworm's innate preference for the tomato plant.
DIAPAUSE

Adult CPB enter diapause primarily in response to short day lenghts. However.
low temperatures. senescent foliage. or a non preferred host greatly enhance the
diapause-inducing effects of photoperiod (de Wilde and Ferket 1967 , Hsiao 1978. Hare
1983). This phenotypic variability allows the beetles to adapt to local conditions even
under day lengths that would consistently prevent diapause (Tauber at al 1988a). Fifty
five years after CPB introduction and first establishment in Europe. the beetle has
spread throughout almost all of continental Europe and had developed a substantial
degree of photoperiodic difi'erentiation. Northern populations exhibit a larger critical
photoperiod than southern populations. the difference being approximately 1 .5 hours
(de Wilde and Hsiao 1981). This range of variability is less than that found among North
American populations. Among the later. the critical photoperiod ranges from about 15
hours (Logan. UT) to fewer than 13 hours (Benson. AZ) and a population from Roma-Los
Saenz, TX., shows very little response to photoperiod (de Wilde and Hsiao 1981).
However. comparisons between North American and European populations are
complicated by the fact that food quality and species play an important role in diapause
induction (de Wilde et a1 1969. Hsiao 1978. Hare 1983). European beetles are largely
restricted to cultivated potato. whereas North American beetles have several wild
solanaceous hosts to which they are variously adapted (Hsiao 1978. de Wilde and Hsiao

1981. Jacobson and Hsiao 1983). The restricted availability of food plants could

9

strongly influence the phenology and adaptation of European populations. The
enormous flexibility of CPB in diapause and voltinism characteristics has undoubtedly
contributed to its success in invading new habitats (Ushatinskaya 1966. Tauber et al
1986. Horton and Capinera 1988).

CPB leave the food plant. move to the edges of fields. and burrow 10 to 70 cm in
the soil to hibernate (Minder 1966); positive geotaxis and negative phototaxis guide
movements during this period (de Wilde 1954 in Tauber et a1 1986). In the state of New
York, many CPB first generation adults enter diapause. A substantial number of these
do it after ovipositing briefly (Tauber et al 1988a). In the USSR. approximately one-half
of the females oviposit. one fifth oviposit some eggs and one fifth enter diapause
without ovipositing (Ushatinskaya 1966).

HOST PLANT RESISTANCE

Feeding deterrents are responsible for the resistance of the majority of
solanaceous and non solanaceous plants (Hsiao and Fraenkel 1968c). Extensive
screening by Schalk et a1 (1970) of over 1500 clones of the ancestral S. tuberosum
subspecies andigena failed to detect any resistance to CPB. Hence. it appears unlikely
that S. tuberosum will provide any genetic sources that might be of value in breeding
for CPB resistance (Dimock and Tingey 1985). CPB tolerate the glycoalkaloids found on
S. tuberosum foliage (Melville et al 1985). S. chacoense is one of the most resistant of
the wild tuber-bearing Solanum species to CPB. but the level of resistance varies widely
within the species (Sinden et al 1986). S. chacoense clones with high leptine
(glycoalkaloids) are highly resistant to larvae and nearly immune to CPB adults
(Sinden et al 1986). Trichome exudate of S. polyadenium . a wild mexican species with
type A hairs only. encased the tarsi of first instar CPB larvae. interfering with their
ability to grip the plant (Gibson 1976b in Dimock and Tingey 1985). Only 14% of dead
larvae collected from S. berthaultii sufferred from tarsal encasement by the trichome

exudate. compared to 96% on S. polyadenium and one on potato. The highest mortality

10

on S. polyadentum occurred during the first instar. young larvae being highly
susceptible to entrapment in the trichome exudate (Dimock and Tingey 1985). High
mortality in CPB first instars due to chronic intoxication or malnutrition is reported
for S. berthaultii (Groden and Casagrande 1986).

Although it has been recognized that food-plant selection in CPB is based on a
complex of stimuli. several studies have stressed an important role for alkaloids as
feeeding deterrents and toxins. The alkaloids are thought to restrict the host range of
beetles and reduce feeding on "resistant" plants (Hsiao and Fraenkel 1968. Hsiao 1974.
Sinden et al 1978. 1980. Dimock and Tingey 1985). In several papers. authors imply. or
explicitly state. that alkaloids act directly on the chemosensory system to inhibit
feeding. As a result. it has become generally accepted that alkaloids exert a strong
influence on the host choice behavior of CPB. However, variable acceptance of host
plants among regional populations of CPB has evolved independently of adaptations to
alkaloids at the sensory level (Harrison and Mitchell 1988).

Plant resistance in Solanum plants slows population increase through negative
impacts on growth and reproduction. In general. larvae fed on S. tuberosum developed
more rapidly. had lower mortality. and higher size and weight. than did those fed on
wild Solanum species (Latheef and Harcourt 1972. Hsiao 1974, 1978. de Wilde and Hsiao
1981. Melville et al 1985. Horton et al 1988). Some exceptions to this rule had been
found by Hsiao (1978). Hare and Kennedy (1986). and Cappaert (1988). as a result of the
great variability in the CPB populations. For example. Tauber et al (1988b) report that
under field conditions. the development rate of CPB larvae is substantially different
even among individuals of the same egg mass. One of the factors aflecflng this
variability in development rate is larvae feeding on its egg shells. Hsiao (1976) indicates
that the larvae deprived of feeding on egg shell invariably initiated feeding sooner but
required a longer overall feeding period to reach the second instar. especially when

reared on less acceptable plants. Retarded development not only reduces the number of

11

generations that can be completed within a growing season. but might also lead to
increased susceptibility to insecticides and protracted exposure of vulnerable larvae to
the controlling influence of natural enemies and adverse environmental conditions (
Brown et al 1980. Dimock and Tingey 1985). Populations of CPB feeding on tomato. a
suboptimal host species. appear to be more afi‘ected by the parasitoid Myiopharus
dayphorae than populations feeding on potato (Latheef and Harcourt 1974).

The potential of CPB populations to overcome plant resistance is high.
Casagrande (1982) indicates that S. berthaultii deter oviposition to CPB. After two
generations of confinment on S. berthaultit in the field. the beetles no longer
demostrate reluctance to oviposit on this host (Groden and Casagrande 1986).
Furthermore. there is no difference in survival between these larvae that complete its
third generation on S. berthaultii and larvae that had been consistently reared on S.
tuberosum (Groden and Casagrande 1986).

Host plant resistance could also have negative impacts on CPB natural enemies.
Under greenhouse conditions. there is a direct relationship between the density of
glandular trichomes in aphid resistant potato clones (S. tuberosum x S. berthaultii
.F3. and S. berthaultii ) and adverse effects on aphidiophagous species (eight
coccinellids. two chrysopids and one parasitoid) (Obrycki and Tauber 1984). These
negative effects include a reduction in adult coccinellid searching time and a
corresponding increase in the rapid movements of the adults (Obrycki and Tauber
1984). The mobility of newly hatched coccinellid and chrysopid larvae is inversely
related to the density of glandular trichomes (Obrycki and Tauber 1984). The highest
number of larvae dropped from leaves with medium densities of pubescence. while few
larvae escaped from S. berthaultii leaves bearing high densities of glandular trichomes
(Obrycki and Tauber 1984). The severe negative effects observed under greenhouse
conditions are attenuted in the field (Obrycki and Tauber 1984). In the laboratory.

Edovum puttleri readily attacks and parasitizes CPB eggs on S. tuberosum . but it is

12

entrapped by the glandular trichomes on S. berthaultii . Not only is the parasitism
higher on S. tuberosum . but a great number of eggs are killed (possible due to feeding or
superparasitism) on S. tuberosum than on S. berthaultii (Obrycki et a1 1985). Natural
enemies and moderate levels of glandular pubescence are compatible mortality factors
in the management of aphids and CPB on potatoes (Dimock and Tingey 1985. Obrycki et
al 1985).
NATURAL ENEIIIES

Natural enemies of the CPB are mainly predators. Only two tachinid parasitoids
are found naturaly in the United States. The most common pentatomid predators of the
CPB in the northern states are Perilus bioculatus Fabricius and Podosius
maculiventris Say. Both have been reported to be relatively inefi’ective in controlling
CPB densities in conventional grown potatoes (Tamaki and Butt 1978. Drummond et al
1984). Another pentatomid (Oplomus dichrous ) has a considerable disadvantage in
development in relation to the CPB. especially below 28°C (Drummond et al 1987).
Coleomegilla maculata DeGeer is a polyphagous predator associated with crops
supporting aphids (Wright and Laing 1978). In Michigan. both adults and larvae prey on
eggs and small larvae (Groden 1988). For the foliar searching carabid. Lebia grandis
Hentz. adults are predaceous on eggs and larvae of CPB. and the larvae are solitary
ectoparasitoids on CPB pupae (Groden 1988). She considers this insect as the most
significant predator of CPB in Michigan. and predation on CPB is strongly density
dependent. The tachinid parasitoid. Myiopharus doryphorae main limitation with its
host (CPB) is the lack of population syncrony (Harcourt 1971. Tamaki et al 1983.
Horton and Capinera 1987. Groden 1988). For the CPB egg parasitoid. Edovum puttleri .
an inverse relationship between incidence of parasitism and age of the host has been
reported ( for both the Colombian and Mexican biotypes) (Rubertson et al 1987). An

extensive literature review of the CPB natural enemies is reported in Groden (1988).

13

HORSENETTLE

Horsenettle, Sotanum carolinense L., is a prickly. perennial plant. 30-100 cm.
having a very extensive and deeply penetrating root system which permits storage of
large reserves (Darlington et al 1951. Illnicki et a1 1962). It is normally disseminated by
means of seeds. creeping roots. and root cuttings (Illnicki et a1 1962). Seeds are capable
of germination from depths of 10 cm. and producing seedlings from May through
August (Illnicki et al 1962). Plants may arise from small vegetative root cuttings less
than 3 cm long and 0.5 cm in diameter (Wehtje et a1 1987). Shoots may arise from
adventitious buds found on the tap root section from depths of 30 cm (Illnicki et al
1962). Roots of horsenettle act a the major sink for photosynthate accumulation at the
0.2 to 0.5 bloom growth stages (Garrel et al 1988). while the starch content of the storage
roots was about 36% prior to emergence in the spring. declined to 13% at flowering. and
increased by late summer to the original level (Pagano 1974).

Horsenettle is a native of the southern part of the United States. but is spreading
northward. where it is becoming common in places. Horsenettle distribution is through
all the eastern half of the United States except Maine. north into southern Ontario.
west from Oregon and California east to the Rockies in southern Idaho and Arizona
(Illnicki et al 1962. Pagano 1974. Allan 1978). This plant was of occasional occurrence
in Michigan by 1904. but is becoming a serious weed in parts of the state. and is
gradually spreading from the south to the north (Darlington et a1 1951).

Horsenettle acts as an important host for insects of economic important crop
plants. It is a host plant for the potato psyllid (Paratrioza cockerelli Sulc.). Other
important insects harbored by this plant are as follows: potato flea beetles (Epitrix
fuscula Crotch and E. cucumeris Harris). Colorado potato beetle (Leptinotarsa
decemltneata Say). potato stalk borer (Trichobaris trinolata Say). onion thrips

(Thrips tabaci Lind) and greenhouse red spider mite (Tetranychus telartus L.) ( Illnicki

14

et al 1962). Snapbean yield is reduced 14 to 74% when infested with horsenettle (Frank
1988).

The major problem in controlling this weed is the regrowth potential of the
storage roots which can repeatedly produce new shoots as tops are removed (Pagano
1974. Wehtje et a1 1987). The results of some researchers (Illnicki et al 1962, Bradbury
1956 in Pagano 1974) indicate that cultivation actually enhanced the problem since the
weed is capable of reproducing from small root sections. Bradbury (1954) in Pagano
(1974) observed differences in growth patterns between disturbed and undisturbed
infestations of the weed. The older undisturbed areas were less thickly populated with
horsenettle than were cultivated. Under non-agricultural environments. horsenettle is
found in open, sparsely vegetated areas, forming fairly large but often widely dispersed
patches (M. L. May unpublished observations 1981 in May and Ahmad 1983). where
grass competition is minimal (Pagano 1974).

This plant is likely to persist along the edges of cultivated fields. along
roadsides. and in waste ground (Darlington et a1 1951). but it has been noticed most
frequently in corn, followed by pastures. alfalfa. potatoes. and tomatoes. with the most
intensive infestations occurring in fields where corn had been grown for several years
(Illnicki et al 1962. Pagano 1974).

In the eastern of the United States. the native horsenettle. has served as an
important alternate host for the Colorado potato beetle. and it is a natural host for a

related Leptinotarsa species. Leptinotarsajuncta (Hsiao 1985).

MANUSCRIPTI

DEVELOPMENT AND SURVIVAL OF TWO POPULATIONS OF

COLORADO POTATO BEETLE (WIEOI’IERA: CHRYSOLEELIDAE) ON HOW

Solanum carelinense I.

15

16

ABSTRACT

The Colorado potato beetle (CPB). Leptinotarsa decemlineata (Say) has been very
successful in exploiting a variety of native and cultivated solanaceous plants in a wide
range of habitats. The population dynamics of CPB on horsenettle was determined through
field experiments. Development rate and survival on two host plants was evaluated in a
laboratory study. The optimum sample size for studying CPB on horsenettle is calculated.
Accumulated mortality for CPB egg and larvae stages was higher than 90%. Predators
with chewing mouthparts were more abundant early in the season, and predators with
sucking mouthparts late in the season.There were no differences in development rate,
pupal weight or survival for two beetle populations on potato or horsenettle foliage. CPB
has been very selective for laying its eggs on horsenettle. CPB has been able to feed
efficiently on horsenettle plants while keeping its ability to exploit potato plants, and a

probable difference in oviposition behavior is developing.

17

The Colorado potato beetle (CPB) .Lepttnotarsa decemlineata (Say). has been
very successful in exploiting a variety of native and cultivated solanaceous plants in a
wide range of habitats (Hsiao 1982). It is believed that buffalo bur .Solanum rostratum
L., was the principal North American host of CPB before the introduction of potato ,S.
tuberosum L. in the 1800's (Power 1906, Hsiao 1981. May and Ahmad 1983, Casagrande
1986, 1987). While the majority of CPB in the north. central and eastern United States
feed on cultivated potatoes. many found in the southern states feed on native hosts
(Hsiao 1978). In the Great Plains of the United States. bufl'alo bur is the predominant
host. Silver night shade. S. elaeagny'olium is a secondary host in the southern plains,
and a principal host in Arizona. where buffalo bur is not prevalent (Hsiao 1978). In
several central and south eastern states, the horsenettle. S. carolinense is an
important native host (Hsiao 1978).

The CPB is highly adaptable and capable of further expanding its host range and
geographic distribution (Hsiao 1982). Distinct differences exist among local geographic
CPB populations. For example. their ability to survive on several wild hosts.
particularly S. elaeagnifolium . has been determined by Hsiao (1978. 1981), Hare and
Kennedy (1986). In a comparative study of eleven United States and European beetle
populations, Hsiao (1982) indicates that Arizona beetles have a unique ability to
survive on S. elaeagnifolium . All populations survived uniformly well on potato,
suggesting that the ability of southwestem CPB populations to survive on wild hosts is
independent of their ability to survive on potato (Hsiao 1978. 1982). Substantial
geographic variation in host species utilization suggests that New England L.
decemltneata populations differ from populations in the southwestern USA and
Europe in their ability to utilize S. dulcamara (Hare 1983). There were clear differences
in the ability of Colorado potato beetles collected from different commercial potato-
growing regions along the east coast of the United States to sunrive on horsenettle. For

examme. North Carolina CPB exhibited significantly greater rearing success than

18

Connecticut beetles. The North Carolina population has expanded its host range to
include horsenettle without losing its ability to survive on potato (Hare 1986). Host-
adapted populations are developing among geographic populations of the CPB in North
America (de Wilde and Hsiao 1981. Hsiao 1978. 1982). but this is likely to occur only
when populations are isolated from each other and from normally preferred optimal
hosts (Hsiao 1978).

At the Michigan State University Kellogg Biological Station (KBS). Hickory
Corners. M1 the CPB population utilizes horsenettle. and has probably been restricted
to this host since 1954. when farmers quit growing potatoes in the area. This
population provides an opportunity for investigating the possible existence of a host-
adapted population. The purpose of this study was to investigate the population
dynamics of the CPB in Michigan on its wild host plant. horsenettle. A second objective
was to determine whether development and survival rate differ between Michigan CPB
populations originating from potato and horsenettle plants. Using the variability of
the sampling data of CPB on horsenettle. the sampling size for studing this insect was

calculated.

MATERIALS AND METHODS

Site description: All field work was conducted at the Bird Sanctuary of KBS.
Hickory Corners. MI during the summer of 1987 and 1988. In 1987. CPB were monitored
in contiguous three different horsenettle stands: 1) the Weed Field (2 ha) had been
uncultivated since harvest of a corn crop the previous year. Horsenettle plants were
successful early in the season. but were overshadow or weaken by competition with
other weeds like lambsquarter. red dock and rag weed by the beginning of July.

Horsenettle density represented 20-30% of the weed population in that field. 2) The

19

Corn Field (5 ha) was planted with corn in 1986. 1987. and 1988. The variety used was
Great Lakes 579. sown at a density of 60000 plants/ha. and 90 cm distance between
rows. Horsenettle was the dominant weed and only a small population of velvetleaf was
present (less than 10% of weed population). Finally. 3) the Grass field (10 ha) was sown
with a mixture of timothy grass (2 kg/ha) and orchard grass (3kg/ha) on May 1987. This
field had been fallow for the two previous growing seasons. Due to poor germination of
the grass seed. this field could be considered a second weed field. Velvetleaf and pig weed
were the other weeds present in this field. with velvetleaf overgrowing the others by the
middle of July. Horsenettle density represented approximately 50% of the total weed
population. In 1988. the Corn field(2) was the only study site. No pesticides were used in
the study area in 1987 or 1988.

Stage-specific survival: In order to evaluate the impact of environmental factors
on the development of the CPB under field conditions. age-specific survival was
calculated from CPB measurements. In 1987. weather data were obtained from the
climatological station located about 500 m east of the research plots. During 1988. a
hygrothermograph in a standard meteorological weather shelter was located between
the Corn and the Grass fields. It was used to gather daily temperature and humidity
data. Degree-day accumulations were calculated from weather data using the direct
method. A lower threshold of 10° C was used to calculate the mean accumulated degree
days (DD 10) for CPB development (Logan and Casagrande 1980). Residence time for eggs
was estimated as 72 DDlo (Logan et a1. 1985). 41 DD 10 for lst instars. 39 DDlo for 2nd
instars. 49 DD 10 for 3rd instars. and 76 DD 10 for 4th instars (Groden and Casagrande
1986).

The mortality estimate was calculated with Southwood's graphical method as
described by Helgensen and Haynes (1972). This involved estimating the absolute
density of each instar in the field until all larvae had pupated. Since the instars occur

simultaneously over a relatively long period of time. a population curve for each instar

20

was made by plotting the absolute densities against time (in DDlo). Numerical
trapezoidal integration was used to calculate the area under the curve (total incidence).
The actual number to enter a specific instar was calculated by dividing the total
incidence of that instar by its residence time. Using the actual number entering each

instar. survival for a specific instar (Sx) was calculated by dividing the number entering

instar (x+ l) by the number entering instar (x).

Field sampling: CPB and its natural enemies were monitored by direct
observation of 100 randomly selected stems. Sampling began with the emergence of the
beetles and horsenettle plants and ended when no insects were found on the plants.

In 1987. plots were sampled weekly between May 29 and July 25. Samples were
taken from a 2 ha area in each field. To estimate parasitism by tachinids. 100 4th
instars were taken from each field on June 25 and dissected in the lab.

In 1988. sampling was conducted every 2 to 4 days from May 24 through July 29.
The sampled area was 4 ha. Tachinid parasitism was determined for 100 4th instars
collected on June 14. 24, July 3 and 12. These larvae were kept in petri dishes filled with
wet vermiculite until they pupated or parasitoids emerged. To study survival and
development of CPB cohorts. individual plants were flagged when an egg mass was
discovered. and sampled every 2 to 4 days. Seventy cohorts were sampled from May 24
to July 15. CPB oviposition rate was also studied. All CPB egg masses found on
horsenettle. corn or other weeds were collected from a 150 m2 area (50 x 3 m) every 2 to

4 days from May 28 to July 18.

Development rate: The efi'ect of host plant species on development and survival
of the CPB was evaluated in the laboratory. Two beetle populations were used: one

collected from the Michigan State University Potato Research Farm. Entrican MI

21

(Montcalm population) under continuous potato cropping; and one collected from KBS
on horsenettle (KBS population).

In experiment one. egg masses from potato (Montcalm population) and
horsenettle plants (KBS population) were collected from the field during the summer of
1988. The egg masses were held in plastic petri dishes (90 x 15 mm) lined with moist
paper. Excessive leaf material was trimmed from the egg mass to reduce food available
to the larvae at hatching time (Groden and Casagrande 1986). Egg masses were checked
daily for 1st instars hatching. Both egg hatching and larval development were
measured at room temperature conditions (26.8 i 2.2°C). In this experiment. a total of
280 lst instars (2 populations X 2 host plants X 7 replications X 10 larvae per
replication) were used. The number of newly molted or dead individuals was recorded
every 24 h and fresh leaves (potato cv Atlantic. or horsenettle) provided. Pupae were
weighed within 24 h after molting. and adults were sexed. Because survival differed
between treatments and replications. data analysis was as an unbalanced design (SAS
GLM procedure. SAS 1982).

Experiment two was designed to determine the effect of horsenettle foliage
quality (new versus old foliage) on the development and survival of CPB from the KBS
population. New foliage was obtained from the upper part of the horsenettle plants. The
foliage was 1-2 weeks. tender. and of a green light color. Old foliage refers to leaves
located at the lower part of the horsenettle plants. with an age of 4-5 weeks. The leaves
were thicker. harder. and the color was dark green. A total of 120 1st instars (2 foliage
conditions x 6 replications x 10 larvae per replication) were used. This experiment was
conducted under the same conditions as experiment one and the same variawa were
reported. The t-statistic was used to test for differences between treatments ('I'I‘EST
procedure. SAS 1982).

CPB sampling : The first step to estimating mortality of the insect on

horsenettle. was to choose a basic population unit to compare densities of the difi’erent

22

life stages. For potato plants. an appropriate sample unit for the above ground stages of
CPB is a single stalk (Harcourt 1964). He also suggests sampling 150-200 potato stalks
for adult beetle estimation and 100 for eggs and larva. Because no sample unit or sample
size has been determined for CPB on horsenettle. the sample unit was defined as one
horsenettle stem (a single stem coming from the ground). and the sample size was 100
stems.

In order to estimate optimum sample size for future studies of CPB on
horsenettle, mean and variance of density were calculated for each sampling date to
determine spatial pattern. Taylor (1961) has shown that the spatial pattern of a large
number of plants and animals can be described with the variance being proportional to

a fractional power of the mean :

s 2 = a '- "lb

where "a" is related to sampling methods. and "b" is a measure of aggregation
( "b .. has a value of 1.0 when the population is randomly distributed. greater than 1.0
when it is a contagious disribution. and smaller than 1.0 when it is a uniform
distribution). Estimated values of "a" and "b" are obtained from the regression of
log(sZ) on log(m) (Taylor 1961).

Additionally. Taylor's equation can be used to calculate sample size. For this
purpose. antilog(m ) and antilog(s 2) are substituted into a sample size formula
(Karandinos 1976. Logan 1981). Because the arithmetic mean is underestimated when
predicted from the regression equation of a logarithmic plot (Finney 1941. Morris 1955.

Bliss 1967 in Ruesink and Haynes 1973), the antilog(s 2) has to be computed from the

equation :

52 =(a + b bgm + 1.1513545?)

23

where EMS 2 is the error mean square from analysis of variance table of regression
(Bliss 1967). Logan (1981) reports that using the negative binomial to fit the distribution
of CPB egg and larval densities did not produce very good results. He prefers to calculate
the optimum sample size with Karandinos formula (Karandinos 1976). The same
formula was thus chosen for this study. but using a fixed percentage of the mean instead

of the coeflicient of variation as shown below:

N=l2a/2 w)2 s2 / m2
where: Za/z = Value from the Z table
D =Fixedproportion ofthemean
s 2 = Antilog of variance from Taylor's regression

m = Antilog ofsample mean

The first step to define optimum sample size was to determine if data from both
years could be pooled. since sampling size was fixed to 100 stems in 1987 and 1988.
Regression equations (log 5 2 on log m) were calculated as well as a confidence interval
for the slope using a t—value (Sokal and Roelf 1960). The data could be pooled if the
confidence intervals overlap (p = 0.05). otherwise it would be necessary to analyze each
year separately.

Horsenettle sampling: In order to support data from beetle sampling. the spatial
distribution and sample size of horsenettle plants was determined following the
methodology described for the insects (spatial distribution estimated with Taylor's
power law. and sample size with Karandinos formula). Horsenettle density was
estimated by counting the number of stems in randomly—selected 1 m2 quadrats.
Horsenettle density in 1987 was sampled in the Weed Field on May 29. June 15 and July
5. and in the Grass and Corn Fields onJune 20 and July 22. Horsenettle density in 1988

was recorded on May 24. June 4. June 15. June 28 and July 15. In order to estimate CPB

24

density per m2. the mean number of insects per horsenettle stem was multiplied to

horsenettle density at each particular sampling date.

25

RESULTS AND DISSCUSSION

Stage-specific survival 1987

The degree day (DDIO) accumulation started on May 26. three days before the
first adult beetles were observed in the fields. The numbers of insects per horsenettle
stem were multiplied by the stems per meter square to obtain beetle density.
Horsenettle density was sampled twice in the Corn and Grass fields. at 270 and 760

DD 10. and three times in the Weed field. at 60. 270 and 540 DD 10 (Figure 1). A linear

increment of plant density was assumed between sampling points. This linear
increment was observed again in 1988 during the first 500 DD 10 (Figure 2). Horsenettle
sampling started one week earlier in 1988 than in 1987; the sampling in 1988 was done

only in the Corn field.
Adult beetle populations from overvvintering peaked at 130 DDIO, and summer

adults at 380 DD 10 for the Weed and Grass fields (Figure 3). However. the summer
generation in the Corn field peaked at 800 DDlo (Figure 3). Beetle densities were
similar between the Weed and Corn fields. while the densities in the Grass field were
about four times lower. This low density was related to fewer horsenettle plants on the
Grass field (Figure 1). The higher egg densities for the three fields were found at 130 and
500 DD 10. and the lower densities observed between 300 and 400 DD 10 (Figure 4a. b. c).
The Weed and Grass fields had similar egg densities (Figure 4a. c). and they were about
four times lower than in the Corn field (Figure 4b). Even though the horsenettle density
was similar in the Corn and Weed fields. the egg input was different. This maybe

explained by the resource concentration hypothesis of Root (1973). In the Corn field.

26

horsenettle represented over 90 % of the weed population. In the Weed field . horsenettle
plants were only 20-30 % of the weeds present. This may facilitate CPB finding of its
host plants among the Corn plants. while the mix of other weeds made oviposition on
the horsenettle more difficult. The odor of solanaceous plants releases the upwind
locomotory response in CPB. and attracted the beetles in the vicinity of these plants (de
Wilde 1976. Visser and Ave 1978). Visser and Ave named this odor "green leaf volatiles"
and considered the concentration ratios of these volatile components decisive for the
release of a positive anemotactic response in the CPB. This odor is probably directing
flight behavior but clearly directs walking activity (de Wilde 1976). Under field
conditions. walking CPB find potato plants from a distance of 6 m when these plants
are located up wind (de Wilde 1976). In mixed vegetation. however. interaction of the
different odors might prevent the long-range olfactory orientation. Hiding the host
from insects in this way (Visser and de Wilde 1980). leads to associational resistance (a
plant odor being masked by another plant odor. Cromartie 1981). The disruption of
olfactory orientation by the mixing of odors occurs independently of the beetle's
behaviors afier emergence and could have important implications in the population
dynamics of CPB (Latheef and Harcourt 1967. Hsiao and Fraenkel 1968 c. Thiery and
Visser 1986. 1987) (see also egg input discussion below).

The larvae densities kept the same relationship among fields as that reported
for the egg stage (Figures 4a. b. c. and 5a. b. c).

Mortality for eggs. and third instars was higher in the Weed and Grass fields
than in the Corn field. as well as the cumulative mortality (Table 1). These mortaliy
difi'erences were small though. Cappaert (1988) reported similar cumulative mortalities
for CPB on S. angustifoiium in Mexico. But Groden (1988) found that in commercial
planted potatoes, early in the season at the Montcalm Potato Research Farm, the
within generation survival was 0.51. This situation indicated that mortality of the CPB

under undisturbed conditions is very high. but not under the common agricultural

27

environment. The negative mortality reported for the second instar in the Corn field
(Table 1) was probably due to sampling error and therefore is inconclusive. Also
Southwood's method requires at least seven non zero points for each different instar
sampled in order to have accurate estimation of mortality (Ruesink 1975). This
requirement was not fulfilled in 1987. Therefore. the data were used only as a
preliminary evaluation of CPB mortality.

Natural enemies of the CPB found in 1987 on the horsenettle plants were:
phalangids (probably Phalangium opilio ). cocinellids (Coleornegilla maculata and less
commonly Coccinella septempunctata ). pentatomids (Perilus bioculatus and less
commonly Podosius maculiventris ) and nabids (Nabis spp). In the Weed field.
coccinelids and nabids were more abundant early in the season. and pentatomids late
in the season (Figure 6a). Pentatornid populations were well correlated with the second

generation egg stage (Figures 5a and 6a). and it was further supported by the agreement
with the number of egg masses destroyed on the last 400 DDlo (Figures 6a and 7). In the

Corn field. predator counts were low during the first 400 DDlo (Figure 6b). Their
populations were not associated with egg mass number destroyed (Figures 6b and 7). In
the Grass field. pentatomids and nabids represented over 90 96 of the predator counts
(Figure 6c). Their population were closely related to the number of egg masses preyed

uponbypredators (Figures 6c and 7).

Stage-specific survival 1988
Degree day (DD 10) accumulation started on May 23. one day before the first adult

beetles were observed in the field. Beetles began to emerge about 3 to 4 days before the
horsenettle plants. Apparently. that is a common situation both under agricultural

(Lashom 1981 in May and Ahmad 1983) and non agricultural environments (de Wilde
1969. Hsiao 1969). Overwintered beetles peaked at 150 DD 10. The first summer adult

was observed at 400 DD 10. and numbers peaked at 600 DD 10 (Figure 8). Beetle densities

28

were 3 to 5 times higher in 1988 than in 1987 (Figures 3 and 8). Egg density was
approximately three times higher in 1988 than in 1987 during the first generation. and
about the same size for the second generation (Figures 4b and 9). For the larvae stage
only the first instars had two well defined peaks (Figure 10). The larval densities
between years were about twice that of 1988 (Figures 5b and 1 1).

Mortality during the first instar wasvery similar in 1987 and 1988, but not
during the second and third instars (Table 1). The lack of correspondence could be due in
part to the sampling frequency. there were ca. three fold increase in the number of
sampling points in 1988. This inaccuracy of the 1987 data is also reflected in the
negative mortality observed for the second instar (Table l) and the size of the
confidence intervals for mortality estimation as reported in Appendix A.

Soil splashed by rain drops had little or no effect on egg masses (16 eg masses
observed in the field all hatched). The impact of soil splash on the numbers of first
instars hatched, on the other hand. was not quantified. Harcourt (1964) reported rain as
the main cause of the first instar mortality. but it was not found in this study. There
were only 5.88 mm of rain accumulated from April 1 to July 8 during the 1988 season
and therefore rain was not responsible for the 70 % first instar mortality recorded
(Table 1).

Among the natural enemies of CPB found on the horsenettle plants. phalangids
were the most common (Figure 1 1). During the first 150 DD 10, 41 plants with an egg
mass also had a phalangid on the same plant. Of the egg masses. 23 had some or all of
the eggs chewed. Phalangids are one of the CPB mortality factors early in the season.
However. in the literature they are reported as a minor mortality factors. Phalangids
are general predators. and there is a lack of syncrony of their population with the CPB
population (Drummond et al. 1988). Coccinellids (mainly C. maculata ) were sampled

from150 to 400 DD 10 period (Figure 11). and was coincident with the higher egg

densities (Figure 9). C. maculata are reported as predators of eggs and small larvae of

29

the CPB. and their populations are well correlated with the first generation of CPB on
potatoes in Michigan (Groden 1988). A carabid (Labia grandis ) and pentatomids
(mainly P. bioculatus ) were also important mortality factors. both for egg masses and
larvae. Some Lebia were observed searching on horsenettle plants (Figure 1 1). They
actualy overlap the 4th instar population of CPB (Figures 10 and 1 1). Parasitism by
tachinids (Myopharus doryophorae ) was also important ( 17. 21. 8. and 11 %

parasitism at 200. 343. 426. and 562 DD 10 respectively). The maximum parasitism

corresponded with the peak of the 4th instars (Figure 10).

E“ input
CPB egg mass size difi'ered significantly during the season. They were smaller

earlier and late in the sampling period (F(10. 1253) = 9.83. p > 0.0001. Table 2). On potato
plants. Groden (1988) reports similar findings. However. the size of the egg mass was
greater on potato than on horsenettle plants in her study. This could be an effect of host
plant quality. with horsenettle as a sub-optimal host plant for egg mass size. De Wilde et
a1 (1969). Brown et al (1980). Casagrande (1982). Melville et a1 (1985) and Groden and
Casagrande (1986) reported reduced fecundity of CPB when it was fed on plants other
than potatoes.

Total egg input provided an absolute count of eggs laid by the CPB. When this
value was compared with the number of eggs from a random sampling of 100
horsenettle stems. seasonal trends and number of egg per m2 were closely related
(Figures 9 and 12). The exception was for the sampling point at 350 DD 10. This egg input
data (better estimation than data from random sampling) reflected a closer
relationship between the number of eggs and the total population of the natural
enemies (Figures 1 l and 12). Total number of natural enemies were closely related to the

CPB egg density.

30

Some insight on the oviposition behavior of the CPB was also obtained from the

egg input study. The Corn field sampled consisted of corn. horsenettle and a low density
of velvet leaf (less than 10 % of the total weed population). During the first 100 DD 10.

CPB laid more eggs on corn than on horsenettle plants. After 138 DD 10 until the end of

the season more eggs were laid on horsenettle than corn (Table 3). Oviposition on other
weeds was low during the entire sampling period. Oviposition of CPB egg masses on
non-host surfaces is a common phenomenon (May 1981. in May and Ahmad 1983).
Groden (1988) found that about 60% of CPB oviposition was on weeds. Cappaert (1988)
reported ca. 30 96 of the oviposition of a CPB population from S. angustifolium was on
the cage screening. He suggested as the possible reason. that host discrimination occurs.
in part. prior to the alighting of the beetles on the host plant. CPB appears to have poor

short range host recognition. The results shown in Table 3 for the first two sampling
dates. are in agreement with these findings. However. from 138 DD 10 on and especially

after 217 DD 10. the CPB seemed very selective as indicated by laying more than 90 % of
its eggs on horsenettle (Fable 3).

During the first 50 DD 10. when the horsenettle was less than 5 cm. CPB adults
were efiicient in finding the plants prior to oviposition. It is reported that oogenesis
only starts after a period of food intake (de Wilde et al 1969). If the selection of an
oviposition site is the first and primary step of host selection by CPB as stated by Hsiao
and Fraenkel 1968c. Hsiao 1969. Visser and de Wilde 1980. and Ahmad and May 1983.
there are four possible explanations for the results presented on Table 3. One. feeding
and oviposition behaviors are governed by difi'erent mechanisms and the small
horsenettle plants do not provide adequate oviposition cues. In the CPB selection
process for an oviposition site. the physical characteristics seem to play a minor role.
Female lays eggs on surfaces as diverse as hairy and spiny leaves. glass dishes. copper
screens. or paper towels (Hsiao and Fraenkel 1968). Hsiao and Fraenkel (1969) found

that black night shade. S. nigrum . gets twice the number of eggs as potato or S.

31

rostratum plants. However. S. nigrum does not support larval growth and adults rarely
feed on this plant. This observation resembles a case described by de Wilde et a1 (1960).
and Bongers (1970) in Visser and de Wilde (1980). where S. luteum . a toxic plant to
larvae was preferred to potato for oviposition. Therefore. acceptability and suitability
of a plant for feeding are not primarily related to the act of oviposition (Hsiao and
Fraenkel 1968. Hsiao 1969. and May and Ahmad 1983). Chemical stimuli received from
the plant appear to be decisive for selection of an oviposition site (Hsiao and Fraenkel
1968. Hsiao 1969). Small horsenettle plants may not release enough chemicals to
stimulate oviposition.

An alternate explanation was that the Corn field was a simpler environment
that consisted of corn plants. horsenettle. and a small population of non solanaceous
weeds. Therefore. after the horsenettle reached a certain density and size. CPB females
became more efficient in finding the host plants and the plant cues were appropriate for
the CPB to lay the eggs. A third explanation could be that early in the season. the
horsenettle density had less than 6 stems / m2 (Figure 2) and over 90 % of the stem sizes
were lower than 5 cm (Figure 13). On the other hand. the corn density and size (6 plants /
m2 and 10 cm in height) represented a bigger leaf area in the field. Although the beetles
were able to locate the plants for feeding. they had to move frequently to another plant.
and their residence time on the horsenettle plants was smaller . Due to the size and
density of the corn plants, probably the CPB had a higher residence time on them. and
just by chance the females laid more eggs on the corn plants. The last explanation (less
likely) would be to avoid predators that target on the host plant. However. of 4 1 egg
masses sampled on corn and 36 on horsenettle plants. 48 and 52 % respectively were
preyed upon by predators. indicating that the egg masses on the corn plants did not have
an advantage in escaping predation. Also Groden (1988) did not find differences in CPB
egg predation on potato and weed plants. First instars had to move from the corn plants

to horsenettle. and that could lead to high mortality.

32

Comparing the oviposition behavior of the Montcalm CPB population on
potatoes (Groden 1988) with the results obtained in this experiment on horsenettle
(KBS), it is tempting to say that both populations have been under different selection
regimes for egg laying behavior. Larvae hatching from an egg mass laid on a non-host
plant by Montcalm beetles would have a better chance to find its host plant than a larva
under the same conditions for the KBS beetles. Therefore. there was a strong selection
for KBS beetles to oviposit efficiently on its host plant. than for Montcalm beetles.

Using the egg input data. it was possible to evaluate the intensity of egg
predation. The percentage of egg masses destroyed on horsenettle was low at the
begining of the season and increased through time (Figure 14). Comparing the data
from the random sampling (Figure 14). the mortality trends were similar. but the
estimates were always lower under the egg input study. The residence time of the egg
mass exposed to predation and the residence time of the egg mass after predation were
different between sampling methods. In the egg input study. all the egg masses were
removed from the field at each sampling date. As an average they were collected from
the field at 52.6 DD 10 (the residence time is 72 DD 10). therefore. they were exposed to
predation for only 73 % of residence time. In the random sampling. the egg masses were
not collected and remained on the plants. Afier an egg mass is fed upon by a predator. it
remains visible in the field for a certain period of time. If the egg mass was destroyed by
a predator with sucking mouth parts (as it was the case for the majority of egg input
data). it would last in the field for about 173 DD 10 (see cohort study below). Because all
the egg masses preyed upon were collected for the egg input study but not for the random
sampling. a sucked egg mass would be exposed to being sampled 3.3 times more in the

random sampling than in the egg input study.

Cohort study

Egg mortality was estimated at 49.8% (n = 78 eg masses). When comparing this
mortality with Southwood's stage-specific estimation. Southwood's estimate was 14 %
higher (Table 1). probably due to the assumption of the distribution of mortality
through the stage. Southwood's method assumes that mortality is light at the beginning
and heavy at the end of the stage. From the cohort study. it was found that the
accumulated 50% mortality for individual eggs was observed when the egg mass age was
about half of its residence time. and the mortality rate was constant through the stage
(Figure 15). Constant mortality for the egg stage seems reasonable. unless the predators
have some preference for egg masses of a certain age. This preference has not been
reported in the literature.

The last part of the cohort study was related to the natural enemies. Chewing
predators destroyed 12 of 13 eg masses during the first three weeks of sampling.
Predators with sucking mouth parts consumed 14 of 15 eg masses over the next four
weeks. Afier an egg mass is consumed it remains on the plant for several days and could
be recounted on subsequent sampling dates. Data from 28 eg masses indicated that the
average residence time on horsenettle for a chewed egg mass was 82.8 DD and 178.5 DD
for a sucked egg mass. These findings were similar to the data reported by Gmden (1988)

on potato plants.

Development rate
The effect of host on larvae development was significant (F(l.229) = 896.2. p >

0.0001. Table 4). Beetles feeding on potatoes developed faster than those feeding on
horsenettle (Table 4). The slower development on horsenettle must increase larval
exposure to predation and pathological infection. This could account for the higher
CPB mortality on horsenettle than on potatos. Since they may be nutritionally

deficient, insects on horsenettle may also be more susceptible to to insecticides (Brown

34

et al 1980). Potato plants were also a better food source when evaluated by pupal weight.
Male and female pupae weight were similar in relation to the host plant effectfl‘able 4).
Host plant effect was significant for survival of first to adult stages (F(1.24) = 3.05. p <
0.01and F(1.24) = 7.93. p < 0.01 respectively. Table 5). Better survival was observed when
potato was the host plant. independently of the beetle population. Working with three
beetle populations from potato fields. Hare and Kennedy (1986) report difi’erences for
survival on horsenettle. with the North Carolina population better adapted to survive
on horsenettle. Because the last two of the three generations in North Carolina must
seek out and feed on alternate hosts. mainly S. carolinense . the beetles were
conditioned to horsenettle.

Development rate (7.24 vs 7.57% per day), pupal weight (136.2 vs 128.2 mg for
females and 1 1 1.5 and 107 mg for males). and survival (68.6 vs 83.3%) in Montcalm and
KBS beetles were not significantly different when they fed on horsenettle (Tables 4 and
5). This implies that Montcalm and KBS beetles belong to the same population. and 30
years have not been sufficient for the KBS population to adapt to the horsenettle plants.
The majority of research reports indicate that CPB population are better adapted to
potato than to any of its native host plants (Hsiao 1978. Brown et al 1980. de Wilde and
Hsiao 1981. Hsiao 1982. Groden and Casagrande 1986. Hare and Kennedy 1986).
However, Hsiao (1978) indicates that in Arizona CPB is better adapted to S.
angustifolium . more than to any other plant. Cappaert (1988) reports that a CPB
population from Morelos. Mexico. where its native host is S. angustifolium . rarely
feeds on potato plants.

In the experiment about the impact of foliage age on development and survival
of the KBS beetles (experiment two). no significant diiferences were found for larval
deveolpment (t(48) = 1.3. p > 0.37. Table 6) or survival from the first to fourth instar (t(5)
= 1.86. p > 0.51, Table 6). There was a slight indication that on new foliage. beetles

developed faster (8.84 vs 7.41% per day) and survived better (80 vs 75%). Observations

35

on the amount of foliage consumed. indicated that larvae consumed about 40% less
foliage when fed on old foliage. Besides the metabolic effect. feeding also has a
behavioral aspect (Visser and de Wilde 1980). When fed on suitable host plants. CPB
larvae spend most of the time feeding with only short periods of rest. When fed on
unsuitable plants. the larvae spend most of its time wandering and resting. and feed
only for short periods (Hsiao 1969). In feeding tests. de Wilde et a1 (1969) reported that
CPB adults can detect the age of its host plant. Pupal weight was significantly different
both for females (F(l.30) =16.8. p > 0.0003. Table 6) and males (111.56) = 16.9. p > 0.0001.
Table 6). The insects had heavier pupal weights when fed on new foliage than on old
foliage (128 vs I 14 mg and 1 10 vs 101 mg for females and males respectively. Table 6).
- As pointed out by Rafes (1967) pupal weight may be regarded as an index of larval food
consumption. The distribution of the larvae on the horsenettle plants in the field. also
indicates that they were feeding mainly on the new foliage. Harcourt (1964) observed
that newly hatched larvae feed on the egg chorions for a short period of time. as a rule
showing little discrimination between hatched and unhatched eggs. They then attack
the foliage near to the edge of the egg mass before moving to the tap of the plants to
complete their development. Young foliage could have a lower glykoalkaloid
concentrations. Hsiao (1986) found that young foliage in Lycopersicum hirsutum had

50 % less glykoalkaloids than mature foliage.

Beetle sampling

Mean densities of all stages were well below the typical population levels of CPB
on potato plants (Tables 7 and 8). Adult and egg masses per stem had lower standard
error. while first instars had the highest. Since this insect lays eggs in clusters. first

instars dispersing away from the egg masses would have the highest degree of

clustering.

36

Spatial distribution based on Taylor's power law analysis (b values) for egg
masses, larvae and adults were very consistent among fields (Table 9) and between years
(Table 10). Spatial patterns for eggs and adults in 1987 and 1988. showed a pattern best
described by a Poisson distribution based on the b values around 1.0 (Table 9 and 10).
By contrast. larvae had b values greater than 1.0. indicating a negative binomial
distribution (Table 9 and 10). Standard errors were higher in 1987 than in 1988.
Because of the lower sampling frequency. only half as many sampling dates were taken
in 1987 as in 1988 (Table 7 and 8). The non-significance of the regression line for the
larval stage in the Corn Field (b = 1.606. a = 0.908. r2: 0.573, Table 9) could be related to
the high standard error of the mean for first instars (0.51). This standard error was
twice as high as the highest standard error found for any of the other stages sampled
during this study.

Egg mass and larval b values (0.95-1.09 for eggs. and 1.52- 1.57 for larvae. Table
10) were comparable to those reported for potatoes by Harcourt (1963) (1.12 for eggs and
1.45 for larva). and Logan (1981) (1.07 for egg masses and 1.31-1.45 for larvae). This is
an indication that host plant does not affect the aggregation pattern of this insect.
However. the spatial distribution of adults (b = 1.06- 1.16 Table 10) was different than
the patterns described by Taylor (1961) (b=1.48) or Harcourt (1963) (b=1.53). The b
values of this study suggested a Poisson distribution for the adult beetles. while Taylor
and Harcourt report as a negative binomial. However. Taylor (1961) and Logan (1981)
mention that lower slope values reflect the fitting of samples from a lower-density
population. The mean range for Colorado potato beetles at KBS was from 0.01 to 0.29
adults per stem. a low density in relation to the beetle densities on potato plants.
Notably. similar random distribution for adult beetles was observed by Harcourt (1963)
for densities lower than 0.5 beetles per potato stem. In fact. this may apply to other

insects like the cereal leaf beetle. Oulema melanopus where the mean and variance are

37

nearly equal at densities ranging from 0.01 to 0.5 insects per sample. fitting a Poisson
distribution (Ruesink and Haynes 1973. Logan 1980).

Spatial distribution can be used not only to describe the aggregation pattern
characteristic of the species. but also to determine the sample size required to estimate
population parameters. Confidence intervals for each stage indicate that all slopes (b
values) overlap when comparing the different fields (Table 9) and years (Table 10).
Therefore data was pooled. Pooling the data decreased the magnitude of variation both
between fields (Table 9) and between years (Table 10). The optimum sample size
analysis for egg masses or adult densities below 0.5 per horsenettle stem. indicated that
100 stems per sampling date resulted in a 30% precision (Figure 16a and 16b). However.
the larval stage would require at least twice the sample size for similar precision with
the densities of the CPB on the horsenettle stems (Figure 16c).

OptMum sample size for estimation of beetle densities on horsenettle plants
was about 3 fold higher for eggs (Figure 16b). and 10 fold higher for larvae (Figure 16c).
than reported for the beetles on tomato (Latheef and Harcourt 1973) or potato plants
(Logan 1981). The suggested optimum sample size for adult beetles was 3 fold higher in
relation to the sample size indicated for this insect on tomato plants (Latheef and
Harcourt 1973). Even though the aggregation patterns of CPB egg masses and larvae
were similar in horsenettle and potato plants. the sample size required to estimate the
same population level was much higher on horsenettle. The spatial pattern of the host
plant may have a considerable impact on the aggregation pattern of the insect. because

the potato plants were uniformly distributed while horsenettle plants were not.

Horsenettle sampling
Horsenettle density in 1988 changed from 2 plants per m2 on May 24 to 15

plants per m2 on June 28 (Figure 2). The plant density through time could be described

38

with the following equation obtained with the mean stem densities of the six sampling

dates:

y= 0.88979 + (1 / 4.6151 e2") - (1 / 3.7164 M)

where y = horsenettle stems / m2. and

x=timeindegreedays(base 10)

with an r2 = 0.977. The slope (b ) for horsenettle density during 1988 was 1.68.
indicating an aggregation pattern. This could be explained in part by the ability of the
plants to reproduce through rhizomes or by seeds that are not moved too far away from
the mother plants ( Illnicki et al. 1962. Pagano 1974. Wehtje et al 1987). Taking 50
samples of the horsenettle stem density with the 1 m2 quadrat. produced an estimation

of the horsenettle density within 30% of the mean in 1988 (Figure 17).

39

CONCLUSIONS

Mortality estimation higher than 90% for the CPB egg and larval stages
observed during the two years of study. indicates that CPB populations are better
regulated under non-agricultural conditions.

The principal biotic agents for control of CPB populations early in the season
are insects with chewing mouth parts. especially the coccinellid Coleomegilla maculata
, and the carabid Lebia grandis . Their populations being closely associated with the
higher CPB egg input.

Late in the season, the pentatomid Perilus bioculatus is one of the more
important predators on CPB eggs. and along with Lebia beetles. are a strong mortality
factor for CPB fourth instars. Also. the tachinid Doryophorophaga doryphorae is
responsible for 8-21% mortality for CPB fourth instar and prepupae.

Mortality during the egg stage due to predation is constant through the egg mass

age. The residence time for a chewed egg mass is 83 DD“) and for an egg mass preyed
upon by sucking predators. is 179DD 10.

Better development rate. pupal weight and survival were found for beetles
feeding on potatoes when contrasted to feeding on horsenettle plants. Beetles from a
potato population (Montcalm) had similar larval growth as a beetle population from
horsenettle (KBS) when feeding on horsenettle foliage. This supports the idea that CPB
has been able to feed efficiently on horsenettle plants while keeping its ability to
exploit potato plants. However. there was a slight indication that KBS beetles have been

under a strong selection pressure for laying the majority of its eggs on host plants and

40

that could be the first step for initiating the development of a CPB biotype on the

horsenettle population. It would be worthwhile to test this hypothesis further.

41

Table l . Southwood's stagespecific mortality for the Colorado potato beetle on

horsenettle at Kellogg Biological Station. Hickory Comers. MI.

FIELD EGG 1,1 L-2 1,3 ACCUM. MORT.
WEED 0.85113 0.3977 0.8491 0.5715 0-9942
CORN 0.7313a 0.5922 -0. 1407 0.0968 0.8870
0.6582b 0.4715 0.2784 0.4368 0.9201
GRASS 0 852981 0.4246 0.8420 0.5715 0.9943

a Mortality within the stage, date from 1987.

b Mortality within the stage. data from 1988.

C ACCUM. MORT. = Accumulated mortality from eg stage to third instar.

42

Table 2. Changes in the Colorado potato beetle egg mass size on horsenettle at the

Kellogg Biological Station. Hickory Corners . MI in 1988.

DD3 Nb EGG MASS SIZE : S.EC F valued p
57 16 14.9: 2.2 a‘3 (10.1253)=9.83 0.0001
100 38 25.1: 1.7 b

561 10 28.1: 2.1 b c

464 88 292: 1.4 b c d

415 54 29.4: 1.5 b c d

267 244 30.5: 0.6 b c d

217 227 321: 0.8 c d

138 106 32.21: 1.2 c d

171 ' 249 33.5: 0.7 c d e

319 142 34.4: 1.1 d e

371 90 37.9: 1.3 e

a DD = Degree days base 10°C. accumulated since May 24.

b N = Number ofegg masses collected from 130 m2.

C Average number of eggs per egg mass.

d F value based on GLM test.

3 Means followed by the same letter are not significantly difi‘erent. Duncan test (p =

0.05).

43

Table 3. Egg mass distribution on difi‘erent plants from a Colorado potato beetle
population adapted to horsenettle at Kellogg Biological Station, Hickory

Corners MI in 1988.

NUMBER OF EGG MASSES IAID ON b

DDa HORSENE'ITLE CORN OTHER PLANTSc
57 20 1 13 28
1CD 45 90 23
138 106 52 44
1 71 249 54 18
2 17 224 12 8
267 239 3 1
3 19 145 1 2
37 1 90 1 l
4 15 56 1 2
464 78 2 3
561 10 O O
636 O 0 O

a DD = Degree days base 10°C, accumulated since May 26.
bEggmassescollectedfrornanareaof l30m2.

c Mainly velvet leaf. A few egg masses were laid on dry sticks.

44

Table 4. Larvae development and pupae weight of two populations of the Colorado

potato beetle on potato and horsenettle plants in 1988.

BEETLE HOST mm RATE PUPAE warmer.)
PCPUIATKN PIANI‘ (%/DAY :sEa W MAIES
Montcalm Potato 9.99 : 0.39b 153.4 : 3.2C 139.1 : 2.3d
Montcalm Horsenettle 7.24 :l: 0.68 136.2 i 2.8 1 1 1.5 i 2.6
KBS Potato 9.89 :l: 0.5 1 149.0 1 2 .2 127.9 :l: 2 .3
KBS Horsenettle 7.57 : 0.95 128.2 : 2.9 107.0: 2.3

a From the first to the fourth instar.
b Significant difi'erences only for the host plant effect. GLM test (F(1. 229) = 896.2,
p < 0.(IX)1).
c Significant difi‘erences for beetle populations. GLM test (F( 1. 1 12) = 10.17. p < 0.0002);
and host plant effect (F(1. 112) = 99.91. p < 0.0001).
d Significant differences for beetle populations. GLM test (F(1, 105) = 4.77. p < 0.03): and

host plant effect (F(1. 105) = 44.29. p< 0.0001.

45

Table 5. Survival of two populations of the Colorado potato beetle fed on two different

host plants under laboratory conditions in 1988.

 

 

BEETLE HOST SURVIVORSHIP (% : S.E)a
POPULATION PLANT L1 - L4 L1 - ADULT
Montcalm Potato 91.43 : 2.61b 87.14 : 4.20c
Montcalm Horsenettle 68.57 :l: 9.86 67.14 i 9.69
KBS Potato 96.25 i 2.63 93.75 i 3.24
KBS Horsenettle 83.33 i 7.60 78.33 i 7.03

a Insects reared in petri dishes under room temperature (26 : 2.4°C).

b Significant difi'erence only for the host plant efi'ect (F(1, 24) = 3.05. p < 0.001). GLM
test. data transformed to Are Sin Square Root of Percentage (Bliss 1967).

C Significant difi'erence only for the host plant effect (F(1. 24) = 7.93. p < 0.01). GLM test,

data transformed to Are Sin Square Root of Percentage (Bliss 1967).

46

Table 6. Larvae development and pupae weight of a Colorado potato beetle population

on two different foliage conditions of horsenettle plants in 1988.

FOLIAGE DEVELOPMENT PUPAE WEIGHT SURVIVAL
AGEa RATE (mg : S.E) (% : S. E)
(% / DAY : S. E)b FEMALES MALES
NEW 8.84 : 0.9c 128.8 : 2.7d 1 14.0 : 2.76 80.0 : 6.8f
OID 7.41 : 1.06 110.0: 3.8 100.5: 2.0 75.0: 6.7

a New foliage was obtained from the upper part of the horsenettle plants. Its age was 1-2
weeks, tender texture and the color was light green. The old foliage refers to leaves
located at the lower part of the horsenettle plants. Its age was 4-5 weeks. the leaves
were thicker and harder. and the color was green dark.

b Reared in petri dishes under room temperature (26.6 i: 2.4°C).

C Difi‘erences non significant. T-test (t(48) = 1.30. p > 0.37).

d Differences significant. GLM test (F(]. 30) = 16.8. p < 0.001).

e Differences significant. GLM test (F(1. 56) = 16.9. p < 0.0001).

fDifferences non significant. T-test (t(5) = 1.86. p > 0.51). The data was transformed to

Are Sin Square Root of Percentage (Bliss 1967).

47

Table 7a. Mean. variance and standard errors of the different stages of the Colorado

potato beetle on horsenettle during the surmner of 1987. Weed Field.

DATE STATI STlC EEG L - 1 L - 2 L - 3 L - 4 ADULTS
MASSES
MAY 29 MEAN a 0.01 0.0 0.0 0.0 0.0 0.01
VARIANCE 0.01 0.0 0.0 0.0 0.0 0.01
S'ID. ERROR 0.01 0.0 0.0 0.0 0.0 0.01
JUN 04 MEAN 0.07 0.09 0.02 0.0 0.0 0.01
VARIANCE 0.07 0. 14 0.02 0.0 0.0 0.01
STD. ERROR 0.03 0.04 0.01 0.0 0.0 0.01
JUN 10 MEAN 0.02 0.27 0. 14 0.06 0.04 0.01
VARIANCE 0.02 5.37 0.85 0. 1 l 0.04 0.01
STD. ERROR 0.01 0.23 0.09 0.03 0.02 0.01
JUN 16 MEAN 0.01 0.07 0.05 0.08 0.05 0.0
VARIANCE 0.01 0.2 1 0. l 1 0. 14 0.05 0.0
STD. ERROR 0.01 0.05 0.03 0.04 0.02 0.0
JUN 23 MEAN 0.0 0.0 0.0 0.02 0.06 0.01
VARIANCE 0.0 0.0 0.0 0.02 0.06 0.01
STD. ERROR 0.0 0.0 0.0 0.01 0.02 0.01
JUL 05 MEAN 0.03 0.36 0.0 0.0 0.0 0.0
VARIANCE 0.03 6.04 0.0 0.0 0.0 0.0
STD. ERROR 0.02 0.03 0.0 0.0 0.0 0.0

a Mean number of insects per horsenettle stem, 100 horsenettle stems sampled per
sampling date

48

Table 7b. Mean. variance and standard errors of the different stages of the Colorado

potato beetle on horsenettle during the summer of 1987. Corn Field.

DATE STATISTIC EGG L- 1 L-2 L-3 L-4 ADULTS
MASSES
WEST-MEAN?! ------- 0. 01- ""011- ----- 0.0 ------ 0. (Tn—"070 ""001-
VARIANCE 0.01 0.0 0.0 0.0 0.0 0.01
STD. ERROR 0.01 0.0 0.0 0.0 0.0 0.01
JUN 04 MEAN 0.15 0.02 0.0 0.0 0.0 0.05
VARIANCE 0.13 0.04 0.0 0.0 0.0 0.05
STD. ERROR 0.03 0.02 0.0 0.0 0.0 0.02
JUN 10 MEAN 0.10 1.48 0.14 0.16 0.03 0.03
VARIANCE 0.09 26.31 0.49 0.34 0.03 0.03
STD. ERROR 0.03 0.51 0.07 0.06 0.02 0.02
JUN 16 MEAN 0.05 0.80 0.31 0.23 0.06 0.01
VARIANCE 0.05 13.25 0.94 0.60 0.08 0.01
STD. ERROR 0.02 0.36 0.10 0.08 0.03 0.01
JUN 23 MEAN 0.05 0.02 0.07 0.05 0.2 8 0.03
VARIANCE 0.05 0.02 0.09 0.05 0.63 0.03
STD. ERROR 0.02 0.01 0.03 0.02 0.08 0.02
JUL02 MEAN 0.06 0.12 0.06 0.19 0.26 0.05
VARIANCE 0.06 0.83 0.08 0.40 0.34 0.05
S'ID. ERROR 0.02 0.09 0.03 0.06 0.06 0.02
JUL 20 MEAN 0.0 0.0 0.0 0.0 0.0 0.05
VARIANCE 0.0 0.0 0.0 0.0 0.0 0.05
STD. ERROR 0.0 0.0 0.0 0.0 0.0 0.02

a Mean number of insects per horsenettle stem. 100 horsenettle stems sampled per
sampling date

49

Table 7c. Mean. variance and standard errors of the different stages of the Colorado

potato beetle on horsenettle during the summer of 1987. Grass Field.

DATE STATISTIC EEG L - l L - 2 L - 3 L - 4 ADULTS
MASSEB

MAY 29 MEAN a 0.02 0.0 0.0 0.0 0.0 0.06
VARIANCE 0.02 0.0 0.0 0.0 0.0 0.06
STD. ERROR 0.02 0.0 0.0 0.0 0.0 0.02
JUN 04 MEAN 0. 14 0.09 0.05 0.0 0.0 0. 16
VARIANCE 0. 18 0.24 0.07 0.0 0.0 0. 18
STD. ERROR 0.04 0.05 0.03 0.0 0.0 0.04
JUN 10 MEAN 0. 18 0.56 0.31 0.06 0.05 0.09
VARIANCE 0. 17 4.94 6.34 0.06 0.05 0. l2
STD. ERROR 0.04 0.22 0.25 0.02 0.02 0.04
JUN 17 MEAN 0. l l 0.56 0. 15 0.03 0.01 0.03
VARIANCE 0. 12 10. 13 0.35 0.03 0.01 0.03
STD. ERROR 0.04 0.32 0.06 0.02 0.01 0.02
JUN 25 MEAN 0. 12 0.0 0.09 0.01 0.01 0. l7
VARIANCE 0. 1 1 0.0 0.8 1 0.0 1 0.0 1 0.26
STD. ERROR 0.03 0.0 0.09 0.01 0.01 0.05
JUL 05 MEAN 0.07 0.29 0.0 0.0 0.0 0.06
VARIANCE 0.07 4.39 0.0 0.0 0.0 0.06
S'ID. ERROR 0.03 0.21 0.0 0.0 0.0 0.02

a Mean number of insects per horsenettle stem. 100 horsenettle stems sampled per
sampling date

50

Table 8. Mean. variance and standard errors of the different stages of the Colorado

potato beetle on horsenettle during the 1988 sampling in the Corn Field.

DATE STATISTIC EGG L- 1 L - 2 L - 3 L- 4 ADULTS
MASSES
air-2470511515 ------- 0. (Tu—"01)— ----- 00 ------ 5 Bun-0'0""004-
VARIANCE 0.0 0.0 0 0 0 0 0 0 0 04
STD ERROR 0.0 0.0 0 0 0 0 0 0 0 02
MAY 26 MEAN 0.04 0.0 0.0 0.0 0.0 0.06
VARIANCE 0.04 0 0 0 0 0 0 o 0 0 08
SID ERROR 0.02 0 0 0 0 0 0 0 0 0 03
MAY 28 MEAN 0.07 0.0 0.0 0.0 0.0 0.02
VARIANCE 0.06 00 00 0 0 00 002
STD ERROR 0.04 0 0 0 0 0 0 0 0 0 01
MAY 31 MEAN 0.05 0.01 0.0 0.0 0.0 0.04
VARIANCE 0.05 0.01 0 0 0 0 0 0 0 04
SID ERROR 0.03 0.01 0 0 0 0 0 0 0 02
JUN 04 MEAN 0.03 0.10 0.01 0.0 0.0 0.06
VARIANCE 0 03 0.68 0 01 0 0 0 0 0 57
SID ERROR 002 0.08 001 00 00 002
JUN 06 MEAN 0.07 0.08 0.04 0.02 0.0 0.05
VARIANCE 0 06 0.30 0 08 0 04 0 0 0 09
er ERROR 004 0.05 003 002 00 003
JUN 09 MEAN 0.10 0.08 0.15 0.06 0.0 0.06
VARIANCE 0 09 0.64 0 63 0.18 0 0 0 10
SID ERROR o 03 0.08 0 08 0 04 0 0 0 03
JUN 12 MEAN 0.18 0.49 0.15 0.21 0.01 0.03
VARIANCE 0.17 6.43 0.29 0.90 0.01 0.03
SID. ERROR 0.04 0.25 0.05 0.09 0.01 0.02
JUN 14 MEAN 0.17 0.91 0.09 0.1 1 0.05 0.02
VARIANCE 0 20 18.26 0 12 0 24 0 I7 0 02
SID ERROR 005 0.43 004 004 004 001
JUN 18 MEAN 0.16 0.98 0.28 0.31 0.1 1 0.03
VARIANCE 0 16 19.05 3.36 2 56 0 l6 0 03
SID ERROR 0 04 0.44 0.18 0 16 0 04 0 02
JUN 2 I MEAN 0.15 0.22 0.34 0.12 0.17 0.03
VARIANCE 0 15 1.55 2 81 0 15 0 47 003
SID ERROR 004 0.12 017 004 007 002

a Mean number of insects per horsenettle stern. 100 horsenettle stems per sampling
date.

Table 8 (contvd.).

DATE STATISTIC I‘m L - 1 L - 2 L - 3 L - 4 ADULT
MASSES
JUN24 MEANa 0 19 0.04 046 041 032 00
VARIANCE 0 25 0.06 4 33 l 07 0 54 0 0
SI!) ERROR 005 0.02 021 0 10 007 00
JUN 27 MEAN 0. 16 1.34 0.28 0.32 0.37 0.06
VARIANCE 0 24 34.75 0 79 0 54 0 88 0. 12
S'ID ERROR 0 05 0.29 0 06 0 07 0 10 0.01
JUN 29 MEAN 0. 13 0.52 0. 16 0.25 0.39 0.02
VARIANCE 0 l l 8.52 0 40 0 55 1 05 0.02
S'ID ERROR 0 03 0.29 0 06 0 07 0 10 0.01
JUL 04 M EAN 0. 16 0. 14 0.2 1 0.06 0.23 0. 10
VARIANCE 0.24 1.46 1.34 0 06 0.52 0 l 1
STD ERROR 0.05 0. 12 0. l2 0 02 0.07 0 03
JUL 08 MEAN 0. 12 0.32 0.01 0.08 0. 15 0.06
VARIANCE 0 13 5.90 0.01 0 l l 0 13 0 06
STD ERROR 0 04 0.24 0.01 0 03 0 04 0 02
JUL 16 MEAN 0.09 0.0 0.0 0.03 0.01 0.29
VARIANCE 0.81 0.0 0.0 0.03 0.01 0.41
S'ID. ERROR 0.09 0.0 0.0 0.02 0.01 0.06
JUL 22 MEAN 0.0 0.36 0.0 0.0 0.0 0.28
VARIANCE 0 0 8.86 0 0 0 0 0 0 0.24
SD ERROR 0 0 0.30 0 0 0 0 0 0 0.05
JUL 29 MEAN 0.0 0.0 0.0 0.0 0.01 0. 10
VARIANCE 0 0 0.0 0 0 0 0 0.01 0 09
STD ERROR 00 0.0 00 00 0.01 003
AUG 05 MEAN 0.0 0.0 0.0 0.0 0.0 0.05
VARIANCE 0.0 0.0 0 0 0 0 0 0 0 05
STD ERROR 0.0 0.0 0 0 0 0 0 0 0 02

a Mean number of insects per horsenettle stem. 100 horsenettle stems sampled per
sampling date

52

Table 9. Spatial pattern analysis of the Colorado potato beetle on horsenettle in 1987.

based on Taylor's power law regression.

LARVAE

ADULTS

a p = Statistical significance probability of the log 3 2 on the log m regression.

GRASS

POOLED

WEED
CORN
GRASS

POOIED

WEED

GRASS

POOLED

14

14

0.835 :l: 0. 158
0.705 :l: 0. 159

0.949 t 0.043

1.836 :1: 0.232
1.606 :l: 0.800
1.573 :1: 0.300

1.573 :1: 0.224

N.PC
1.290 1: 0. 144
1.049 i 0. 170

1.156 i 0.056

b NS = Non statistically significant.

C N .P = Not possible to make the calculations.

-0. 193

.0241

-0.069

1.060

0&8

1.256

1.034

0.544

0. 189

0.317

0.868

0.976

0.969
0.573
0%2

0.804

0.952

0.905

0.971

< 0.01

< 0.01

0.01
N.sb
0.01

< 0.01

< 0.01
< 0.01

< 0.01

53

Table 10. Spatial pattern analysis of the Colorado potato beetle on horsenettle in 1987

and 1988, based on Taylor's power law regression.

STAGE YEAR N SLOPE (b) : S.E mm) R2 pa
EGG 1987 14 0.949 : 0.043 -0.069 0.976 < 0.01
MASSES 1988 13 1.094 : 0.074 0.120 0.952 < 0.01
POOLED 27 1.009 : 0.040 0.018 0.962 < 0.01
LARVAE 1987 14 1.573 : 0.224 1.034 0.804 < 0.01
1988 13 1.516 : 0.195 1.000 0.847 < 0.01
POOLED 27 1.543 : 0.14 1 1.014 0.828 < 0.01
ADULTS 1987 15 1.156 : 0.056 0.317 0.971 < 0.01
1988 19 1.060 : 0.77 0.131 0.917 < 0.01
POOLED 34 1.096 : 0.046 0.199 0.946 < 0.01

a p = Statistical significance probability of the log 3 2 on the log m regression.

 

 

 

a 10- —+— CORNFIELD

+1 8'

fl 1

S 6‘

g .

De 4"

g .

a 2- ~ if i

5", i
o I I f 1 I I I I ' I I I ' I fij
0100200300400500600700800
May] June I July

DEGREE DAYS (BASE 10°C)

Figure 1 . Horsenettle density in three different fields at the Kellog Biological
Station during 1987. DD 10 measurements beginning on May 26.

y 8 0.90593 + 458386-27: - 3.6339e-5x‘2 — 5.23256-10x"3

 

 

 

20- 1142-0977

(I! 2

U)

4.1

N

E

M

[II

On

a:

E

(I)
01 I I ' I ' I f I j I
0 200 400 600 800 1000
May June I July I August

DEGREE DAYS (BASE 10°C)

Figure 2. Relationship between horsenettle stem density and sampling date in
the Corn field at the Kellogg Biological Station in 1988. DD 10

measurements started on May 22.

 

 

0.4-
N II
2 0.34
M
E 7
0.2- _._ WEEDFIELD
a . - __._ CORNFIELD
S ‘\ _._ GRASSFIELD
a 0.1- /
0.0 r V I v ' r f T Y R
0 100 200 300 400 500 600 700 800
Marl June | July

DEGREE DAYS (BASE 10°C)

Figure 3. Population density of Colorado potato beetle adults on horsenettle at
the Kellogg Biological Station in 1987. DD 10 accumulation started on

May 26.

EGGS PER M

 

 

0 100 200 300 400 500 6C” 700 8C!)
May I June I July
DEGREE DAYS (BASE 10°C)

Figure 4a. Population density of Colorado potato beetle eggs on horsenettle at
the Kellogg Biological Station in 1987. Weed Field. DD 10

measurements starting on May 26.

a
e
w.
e
n
e

 

new: wwwwww om W... ....L.......A..efl_.om we...

57

 

 

0 100 200 300 400 500 600 700 800
May I June I July
DEGREE DAYS (BASE 10°C)

Figure 5a. Population density of Colorado potato beetle larvae on horsenettle at
the Kellogg Biological Station in 1987. Weed Field. DD 10

measurements beginning on May 26.

 

 

 

 

DEGREE DAYS (BASE 10°C)

Figure 5b. Population density of Colorado potato beetle larvae on horsenettle at
the Kellogg Biological Station in 1987. Corn Field. DD 10

accumulation started on May 26.

2

2

  

 

 

2.0
L-l
1.6 L-2
: L—3
L-4
a 1.2
n.
> 0.8
g 0.4
0.0 A\§r_——_— ;‘
0 100 200 300 400 500 600 700 800
May J1me I July
DEGREE DAYS (BASE 10°C)
Figure 5c. Population density of Colorado potato beetle larvae on horsenettle at
the Kellogg Biological Station in 1987. Grass Field. DD 10
accumulation started on May 26.
0.5 -
O’fi-IERS
3 Q4 _ I COCCINELLIDAE
m a NABIDAE
a Perllus
A. 0.3 - a
m
g 1
0.2 -
K-i
E
a 0.1 -
a.
0.0 — ——”_—‘=———
0 100 200 300 400 500 600 700 800
May I June | July

DEGREE DAYS (BASE 10°C)

Figure 6a. Population density of Colorado potato beetle natural enemies on
horsenettle at the Kellogg Biological Station in 1987. Weed Field.

DD 10 measurements beginning on May 26.

2

2

PREDATORS PER M

 

OTHERS
COCCINELLIDAE
NABIDAE
Perllus

  
  
 

III-IE

0100200300400500600700800

Marl June | July

DEGREE DAYS (BASE 10°C)

Figure 6b. Population density of Colorado potato beetle natural enemies on

PREDATORS PER M

horsenettle at the Kellogg Biological Station in 1987. Corn Field.
DD 10 accumulation started on May 26.

0.5 '5
0.4 "'
COCCINELLIDAE
‘ NABIDAE
0.3 " , .

0.0 -

// -'.:;l...’

0100200300400500600700800

 

   

May | June I July

DEGREE DAYS (BASE 10°C)

Figure 6c. Population density of Colorado potato beetle natural enemies on

horsenettle at the Kellog Biological Station in 1987. Grass Field.
DD 10 accumulation started on May 26.

1.0 1

 

 

 

A

I I I I I I

0 100 200 300 400 500 600 700 800
May I June I July
DEGREE DAYS (BASE 10°C)

FED UPON BY PREDATORS

EGG MASSES PER M

Figure 7. Egg masses preyed upon by Colorado potato beetle predators on
horsenettle at the Kellogg Biological Station in 1987. DD 10

accumulation started on May 26.

3.0

2.5

2.0

1.5

1.0

ADULTS PER M

0.5

 

 

 

0.0 ) V) - fi ' I ' I ' I ' '
0 200 400 600 800 1000 1200
May I June I July I August

DEGREE DAYS (BASE 10°C)

Figure 8. Population density of Colorado potato beetle adults on horsenettle at
the Kellogg Biological Station in 1988. DD 10 measurements beginning

on May 22.

61

 

 

EGGSPERM
3?

 

   

 

0 100 200 300 400 500 Gm 700 8“)
my I June I July I
DEGREE DAYS (REE 10°C)

Figure 9. Population density of Colorado potato beetle eggs on horsenettle at the
Kellogg Biological Station in 1988. DD 10 measurements beginning on

May 22.

LARVAE PER M2

 

 

0 100 200 300 400 500 600 700 800
May I m | July I
DEGREE DAYS (BASE 10°C)

Figure 10. Population density of the Colorado potato beetle larvae on
horsenettle at the Kellogg Biological Station in 1988. DD 10

accumulation started on May 22.

 

 

1.5 -
N 1
E ‘ Perllus
M ' I Lebia
a 1 0 _' I PHALANGIDS
m ' . I COCCINELLIDAE
M
2
<
5
a.
May I J1me I July I
DEGREE DAYS (BASE 10°C)
Figure 1 1. Population density of CPB natural enemies on horsenettle at the
Kellogg Biological Station in 1988. DD 10 accumulation started on
May 22.
80 -
N
2 60 _
5
Gt
g 40 -
In)
20 -
oi

 

o 100 200 300 400 500 600 700
May | June | July
DEGREE DAYS (BASE 10°C)
Figure 12. CPB egg density on horsenettle as obtained from sampling an area of

130 m2

60D
31 DD

1

EIIID

/
r ’-
2 Z
/ I

I
é I
é 2
I ’«I
I / ..

/.
g x:
6 .x.

\\\\\\\\\ \

 

 

0 2 5 lo 15 20
PLANT HEIGHT (CM)

Figure 13. Relationship between horsenettle size and sampling date at the
Kellogg Biological Station in 1988.

_n_ EGGINPUT
_._ RANDOMSAMPLING

EGG MASSES
DESTROYED (96)
t ?

 

 

 

0 100 2&) ' 35X) ' 45X) j 500 ' 320 700 800
I“! I June I July I
DEGREE DAYS (BASE 10°C)

 

 

Figure 14. Estimation based on two sampling methods of the percentage of egg
masses preyed upon by CPB predators on horsenettle at the Kellogg

Biological Station in 1988.

 

y 3 2.4167 + 1.2765x
‘ RA2 s 0%1

ACCUMULATED
MORTALITY (%)

 

 

 

 

o'F'l'l'I'l'I'IfITI
010 20 3040506070

EGG RESIDENCE TIME (DD BASE 10°C)

Figure 15. CPB egg mortality distribution in relation to the egg mass age on
horsenettle at the Kellog Biological Station in 1988.

 

 

 

NUMBER OF STEMS SAMPLED

0.0 0.5 1.0 1.5 20 25 3.0
ADULTS PER STEM

Figure 16a. Sample size needed to estimate CPB adult density on horsenettle.

 

 

 

 

 

G
3 500 1
g 400 -
m ‘
a 300 -
‘0 200 -
8 i
g 100 -
Ell . .
+ fi-
o-w-FFFI—r-I-v-r-I-v-v-FI-f-v-fiw-lw-r-Hfi-r-Fr-I-‘l
0.0 0.5 1.0 1.5 20 25 3.0

EGG MASSES PER STEM

Figure 16b. Sample size needed to estimate CPB egg mass density on horsenettle.

 

 

 

D
2000
1600
U)
S 1200
2 800
O
I; 400
I" 4—4
OI I I I I I I I I j
0 2 4 6 8 10

LARVAE PER STEM

Figure 16c. Sample size needed to estimate CPB larvae density on horsenettle.

 

 

 

350
300
g e.
an 20°
3% 150
Nag 1100
F1 50 ' V
. +
O
0 5 10 15 20 25 30

HORSENETTLE STEMS PER M 2

Figure 17. Sample size needed to estimate horsenettle density based on number

of stems per m2.

ACKNOWLEDGMENTS

Appreciation is extended to Dr. Ed Grafius for his helpful comments and
criticisms during preparation of the manuscript. The Scientific Writing course that he
taught during Fall 1988 paved the way for the realization of this thesis. I also would like
to thank my colleagues P. J. Henry. P. Ioannidis. U. Rahardja and especially J. Sirota
for their valuable suggestions and criticisms during the writing process of the
manuscript.

For his special assistance in the statistical area. the author wishes to thank Mr.

Kenneth Dimoff.

REFERHICES CITED

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Brown. J. J .. T. Jermy. and B. A. Butt. 1980. The influence of alternate host plant on the
fecundity of the Colorado potato beetle. Leptinotarsa decenllineata (Coleoptera :
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Cappaert. D. L. 1988. Ecology of the Colorado potato beetle in Mexico. M.S. thesis.
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Casagrande. R. A. 1982. Colorado potato beetle resistance in wild potato. Solarium
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Casagrande. R A. 1985. The "Iowa" potato beetle. its discovery and spread on potatoes.
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Casagrande. R. A. 1987. The Colorado potato beetle: 125 years of mismanagement. Bull.
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de Wilde. J. and T. Hsiao. 1981. Geographic diversity of the Colorado potato beetle and
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PA. pp 47-68.

de Wilde. J .. R. Sloof. and W. Bangers. 1960. A comparative study of feeding and
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de Wilde. J. W.. W. Bangers. and H. Schooneveld. 1969. Efi'ects of host plant age on
phytophagous insects. Entomol. Exp. Appl. 12: 14-20.

Drummond. F. A.. Y. Suhaya. and E. Groden. 1988. Predation of the Colorado potato
beetle. Leptinotarsa decemlineata (Say) by Phalangirlm opiiio (L.). J. Econ.
Entomol. (in press).

Groden. E. 1988. Studies in the natural mortality of the Colorado potato beetle.
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Lansing.

69

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beetle. LeptinotarSC decemlineata (Coleoptera: Chrysomelidae) on Solarium
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Harcourt. D. G. 1963. Population dynamics of Leptinotarsa decemlineata (Say) in
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Harcourt. D. A. 1964. Population dynamics of Leptinotarsa decemIineata (Say) in
Eastern Ontario. II. Population and mortality estimation during six age
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Hsiao. T. H. 1969. Chemical basis of host selection and plant resistance on
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Hsiao. T. H. 1978. Host plant-adaptations among geogaphic populations of the
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Hsiao. T. H. 1981. Ecophysiological adaptations among geographic populations of the
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(eds). Advances in potato pest management. Hutchinson & Ross Publishing Co..
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(ed). Solanaceae biology and systematics. Columbia Univ. Press, NY. pp 345-
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protein from the Colorado potato beetle (Leptinotarsa decemlineata : Col. .
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70

Karandinos. M. G. 1976. Optimum sample size and comments on some published
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yield loss. In J. H. Lashomb and R. A. Casagrande (eds). Advances in potato pest
management. Hutchinson & Ross Publishing Co.. Stroudsburg. PA. pp 105- 1 18.

Logan, P. A. and R. A. Casagrande. 1980. Predicting Colorado potato beetle
(Leptinotarsa decemlineata Say) density and potato yield loss. Environ.
Entomol. 9: 659-663.

Logan. P. A. R A. Casagrande. H. H. Faubert. and F. A. Drummond. 1985. Temperature-
dependent development and feeding of immature Colorado potato beetles
Leptinotarsa decemlineaia (Say) (Coleoptera: Chrysomelidae). Environ.
Entomol. 14: 275-283.

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738-749.

71

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359.

APPENDIX

APPENDIX

THE JACKNII'E APPROACH TO VARIANCE ESTIMATION FOR SOUTHWOOD'S
STAGE-SPECIFIC MORTALITY.

ABSTRACT
One of the shortcomings of Southwood's method of stage-specific mortality estimation
is the lack of an error term. The Jacknife technique was applied to the estimation of the
variability associated with stage specific mortality calculation for Colorado potato
beetle on horsenettle. Removing up to 20 observations did not afl'ect greatly the
Standard Error / Mean relationship. and it was chosen as the size of the subsample
removed for the J acknife. Except for recruitment to the first and second instar in 1987.
and the second instar in 1988. population estimates had a coefi'icient of variation
approximating 10%. Except for the second instar in 1988. the Jacknife estimates of
mortality were not significantly different from the estimates calculated from the entire
data set in the standard way. The Jacknife consistently underestimated the value of
mortality compared to the standard Southwood's method which also underestimates
stage mortality whenever mortality is not occurring at the end of the stage. J ackrrife is
an acceptable method to estimate the variability of the stage-specific mortality

calculation with Southwood's method.

73

One of the shortcomings of Southwood's method of stage-specific mortality
estimation is the lack of an error term (Southwood 1978). This problem can be
overcome using the J acknife technique. Quenouiolle (1949) introduced this technique
for reducing the bias of a serial correlation estimator based on splitting the sample into
two half-samples. In his 1956 paper he generalized this idea. splitting the sample into 9
groups of size h each. so that n = gh . and explored its general applicability. Tukey
( 1958) broadened the applicability of the Jacknife technique when he used it for
interval estimation. The variance of J acknife estimates has an approximate t
distribution (Miller 1974. Manly 1979) or. for large 9 . an approximate normal
distribution (Miller 1974). The Jacknife is a robust technique. and it has been applied to
infer $1 2 [822 from $12 / $22 . to estimate the variability oflog s2 or log 812 - log
822 ; and to establish a confidence interval on S 2 from s2 (Miller 1974). The successful
use of the J acknife method for estimating variances on key factor analysis is reported
by Manly (1979).

Most advocates of the Jacknife suggest using a variance stabilizing
transformation on the estimator to keep the Jacknife on scale and thus prevent
distortion of the results (Miller 1974). Using computer simulation Manly (1979) found
that the Jacknife works best in mortality key factor analysis when it is applied to the
loge of estimates rather than with direct values.

Of the variety of methods that exist for the analysis of stage-specific frequency
data reviewed by Southwood (1978), only Richard's and Manly's method have a formula
(approximate) for standard error for stage-specific mortality estimation (Manly 1974).
He also applied the J acknife to the estimation of the standard error of stage-specific
mortality for the Kiritani and Nakasuji's method (Manly 1977). He found that the
standard error estimates were usually reasonable. Because there are no reports of

variance estimation on Southwood's method. the objective of this paper was to apply

74

the J acknife technique for the estimation of the confidence limits associated with this

stage- specific mortality calculation.

MATERIALS AND METHODS

The Jacknife estimate of variance was applied to mortality calculated for the
Colorado potato beetle, Leptinotarsa decemlineata (Say) on horsenettle, Solarium
carolinense L. at the Michigan State University Kellog Biological Station at Hickory
Corners. MI. The beetles were sampled by direct observation of 100 randomly selected
horsenettle stems. In 1987 the sampling frequency was approximately one week. and
the area sampled was 2 ha. In 1988. the sampling frequency was 2 to 4 days and the
sampled area was 4 ha. Insect counts were transformed to densities per m2 based on the
horsenettle density. Mortality estimates were calculated with Southwood's graphical
method as described by Helgensen and Haynes (1972). A lower threshold of 10°C was
used to calculate the mean accumulated degree days (DD 10) for Colorado potato beetle
development (Logan and Casagrande 1980). Residence time was estimated as 72 DD 10
for eggs (Logan et al. 1985). 41 DD 10 for first instars. 39 DD 10 for second instars. 49
DD 10 for third instars. and 76 DD 10 for fourth instars (Groden and Casagrande 1986).
The Jacknife estimate is affected by the size of the subgroup used for the Jacknife
process. The most precise form of Jacknife to use is to remove only one observation
from the complete data set (Miller 1974. Drummond 1988). However, the estimate of the
variance is not appreciably altered when removing 2, 3. ..... 5. etc observations (Miller
1974, Drummond 1988). Therefore, the size of the subsample removed for this study was
defined by the percentage of the ratio Standard Error / Mean (Mosteller and Tukey
1977) from densities of eggs. first and fourth instars from five observation dates for the
1988 data set. These difi'erent densities and stages chosen were intended to represent the

variability of the Colorado potato beetle sample data.

75

The variance of estimates was estimated by means of the Jacknife procedure (Manly
1977). The basic idea with the Jacknife technique is to divide sample data into h

comparable sized subsamples. The first subsample is then removed from the full set of

data and the mortality (q -1) is estimated using the remaining data. This provides the
first "partial estimate" (q -1). The first subsample is then replaced . the second removed
. and the second partial estimate (q -2) is calculated. The process is continued in order to
obtain all of the partial estimates q -1 .q -2 . ......... ,q -n . These are then

combined with the estimate q all obtained using the full set of data to form the n

"pseudovalues":
Qaj=nqan-(n-1)q.1 . j=1.2.3. .......... .n
The average of these pseudovalues is the Jacknife estimate for q :
JKq if = nStrrnrr'latory 1:1 / n
The variance of q # is estimated as :
Var(q#) = 1 / n(n-1) nSurnmatory j=1(9#j' q#)2
And the confidence limit (CL) of q 4; is estimated as :
€11le =JKq# i tdf‘ Walk”) / n)
where t is a value from the t table with n -1 as degrees of freedom (see Manly 1977).

In this study. the observations were removed systematically and 10 partial estimates of

mortality were obtained.

"9.)

r. vantages-e “1:4.“ 4...».

rw_pifl_- - elk-1;!
I. .

76

RESULTS AND DISCUSSION

The Standard Error / Mean ratio was highest for first instars and lowest for the
fourth instars (Figure 18). The higher variability observed for the first instar is due
both to the dispersion of recently hatched larvae from the egg mass (Logan 1981) and to
a higher sampling error (Groden 1988). For all stages there was an increase of about 4%
in the variability of the data when one observation was removed from the data set
(Figure 18). Removing up to 20 observations did not greatly afi'ect the Standard Error /
Mean relationship. However. when 40 observations were removed at once. there was a
change of about 20% in the variability of the data (Figure 18). Based on these results. 20
observations was chosen as the size of the subsample removed for the Jacknife
technique.

The estimates obtained with the J acknife of the actual number of individuals
entering the egg and larval stage exhibited a coefficient of variation (CV) of 7. 1 to 23.8%
in 1987 and 7.3 to 17.2% in 1988 (Table 1 1 and 12). Except for the recruitment to the
first and second instar in 1987. and the second instar in 1988. population estimates had
a CV approximating 10% indicating that with the Jacknife estimates. the level of
uncertainty around the mean is small. The higher variability for the second instar in
1987 was due to estimates 2 and 7 that were about 50% lower than the others (Table 1 1).
A similar situation was found for the same instar in 1988. when the estimates 3 and 8
were about 40% lower than the others (Table 12).

Survival was calculated by dividing the number of individuals that entered
stage i + 1 by the number of individuals at stage i . and mortality was obtained by

substracting survival from 1. The variance of the partial mortality estimates of the

77

different life stages was higher in 1987 than in 1988. with first and second instars

having higher variance in both years (Table 13 and 14). In 1987. one first instar

mortality estimate ((1 -2 = - 0.0954) and another for second instar (q -1: -0.1 125) were
negative. while only one negative estimate was found in 1988 (q -2 = -0.0349 for the
second instar). These negative estimates of mortality were not considered for the
J acknife analysis. Negative estimates of mortality occur occasionally with Specific
methods due to sampling error. difi'erential sampling efficiency of the various stages. or
high mortality experienced early in a stage (Mills 1981. Sawyer and Haynes 1984.
Gmden 1988.).

The J acknife estimates of mortality were not substantially different from the
estimates calculated from the full data in the usual way. except for the second instar in
1988 (Table 15). It was found that the confidence limits of the estimates were large for
the 1987 data. and for the second instar in 1988 (Table 15). Because of the size of the
confidence limit for first instars in 1987 and second instars in 1988. the confidence
limit extends beyond the lower limit of 0.0. However. the size of the confidence limit of
the mortality estimates for the egg stage in both years or the mortality estimates for
1988 as an overall indicates a good reliability of the technique.

There was a slight indication that the Jacknife had decreased the estimated
value of mortality (5 cases from 8 in Table 15), which is probably in the wrong
direction. Southwood's method underestimates the number of individuals entering a
life stage. whenever there is mortality occurring earlier than at the end of the life stage.
therefore underestimates stage mortality (Sawyer and Haynes 1984). It is reported that
at least the first and second instars of Colorado potato beetle on potato plants
experience high mortality early in the stage (Groden 1988). These lowered Jacknife
mortality estimates were due to number and size of the higher estimates of mortality

with the partial estimates (q -i'sI in relation to mortality estimate with the full data set

(a l (Fable 13 and 14).

78

One aspect that deserves attention from Table 15 is the size of the confidence
intervals. specifically the first instars in 1987 and the second instar in 1988. The high
variability was coming from two sources. the low estimations of mortality in relation

to the mortality q or the mortality estimates higher than q that will lead to negative
pseudovalues. This could be seen on the mortality estimates for first instars in 1987 (q _

2 = 0.6905. q -6 = 0.6717. and q -7 = 0.0386 while estimate q = 0.3640) (Table 3). In the
case of the second instars in 1988. only one observation is quite different from the
others (q -7 = 0.1 107 while q = 0.5259). but 6 of the 8 mortality partial estimates were
higher than the mortality q . and therefore. they produced negative pseudovalues
(Table 14).

These very low or high partial mortality estimations were possibly due to three
factors:

1.- The size of the subsample removed from the data set led to the difference of
about 8% of greater variability when removing 20 observations, than not removing any
observation at all (Figure 18).

2.- The lower densities reached by the Colorado potato beetle led to a lot of zeros
in the 100 observations per sampling date. The calculation of the mean when the 20
observations were removed was usually higher than the mean from the whole data set.
The majority of these higher means were responsible for the higher partial estimates
mortality. and therefore of the negative pseudovalues.

3.- The size of the subsample removed. defined from the ratio Standard Error /
Mean was calculated using the data from 1988 but not 1987.

The majority of the Jacknife estimates of mortality were very Similar to the
normal estimate with Southwood's method. Due to the low densities of the beetles on
horsenettle. this could be considered a though test for the technique. Therefore. the use
of the Jacknife method for estimating an error term on the mortality calculated by

Southwood's method is ameptable. but should be tested with simulation.

79

Table 1 1. Number of individuals entering each stage estimated with Southwood's
method for estimate stage-specific mortality in Colorado potato beetle on
horsenettle in 1987.

EGGSa L-lb L-2b L-3b L-4b
1C 59.02 21.89 13.92 8.12 5.87
2d 61.75 24.00 7.43 8.26 6.45
3 64.43 14.59 15.98 8.56 6.59
4 66.99 22.84 15.32 7.78 5.19
5 57.71 22.39 15.67 8.83 5.74
6 43.66 25.24 15.39 7.50 5.46
7 69.27 23.82 7.82 7.06 6.45
8 59.58 16.21 15.59 8.57 5.86
9 67.29 22.93 14.82 8.36 5.45
10 49.73 22.30 15.10 8.39 5.74
1 1 50.02 23.89 15.36 8.77 5.97
C.V.C 14.7 16.1 23.8 7.1 8.1
3 Based on 6 sampling dates.
b Based on 4 sampling dates.

C Number 1 refers to data using 100 observations per sampling date.
‘1 Numbers 2 to 1 I calculated using only 80 observations per sampling date.

C C.V. = Coefficient of Variation.

80

Table 12. Number of individuals entering each stage estimated with Southwood's
method for estimate stage-specific mortality in Colorado potato beetle on
horsenettle in 1988.

EGGSa L-lb L-2b L-3C L-4d
16 171.67 60.68 28.77 21.84 13.71
2f 176.63 60.04 32.38 21.99 13.74
3 167.82 56.32 19.79 20.48 11.29
4 156.53 50.35 28.71 20.41 13.96
5 165.80 69.79 32.01 22.47 13.28
6 190.99 66.53 30.79 22.55 16.16
7 182.07 68.24 32.55 22.50 12.63
8 150.91 56.29 19.79 17.60 12.03
9 164.51 50.76 28.71 22.17 13.37
10 180.94 56.36 30.35 23.53 14.97
11 180.19 61.82 32.38 22.73 15.50
C v.8 14 7 16.1 23.8 7.1 8.1

a Based on 15 sampling dates.

b Based on 13 sampling dates.

C Based on 12 sampling dates.

d Based on 10 sampling dates.

C Number 1 refers to data using 100 observations per sampling date.
f Numbers 2 to 1 1 calculated using only 80 observations per sampling date.

g C.V. = Coefficient of Variation.

81

Table 13. Stage-specific mortality estimates for the Colorado potato beetle on

horsenettle in 1987. calculated with the J acknife technique.

EGGS L- 1 L- 2 L- 3
qa 0 6291 0.3640 0 4166 0 2776
q-1b 0 6114 0.6905 -0 1 125 0 2192
q-2 0 7736 -0.0954 0 4644 0 2303
q- 3 0.6591 0.3294 0.4919 0.3334
q-4 0.612 1 0.3000 0.4364 0.3502
0-5 0.4218 0.3905 0.5127 0.2721
q_6 0.6562 0.6717 0.0967 0.0867
q-7 0.7279 0.0386 0.4501 0.3163
q-3 0.6593 0.3538 0.4359 0.3475
q-9 0.5516 0.3227 0.4442 0.3164
q-1o 0.5224 0.3570 0.4293 0.3192
9230;)'5""'66§59 """"" 6 2365d‘""'""0’108§5 """"" 0’ 6543’

a Normal mortality estimate based on 100 observations per sampling date.
b J acknife mortality estimates based on 80 observations per sampling date.
C Jacknife variance . ‘

d J acknife variance estimate based on 9 subsamples.

82

Table 14. Stage-specific mortality estimates for the Colorado potato beetle on

horsenettle in 1988. calculated with the Jacknife technique.

0": .- MJMJWI in.
- 1 '1 '4. - a ‘s- L?!

EGGS L- I L- 2 L- 3
qa 0 6465 0 5259 0 2409 0 3723
q- 1b 0.6601 0.4540 0 3239 0 3752
q-2 0.6644 0.6486 -0.0349 0.4487
q-3 0.6783 0.4298 0.2891 0.3 160
q-4 0.5791 0.5413 0.2890 0.4090
q-5 0.6517 0.5372 0.2676 0.2834
q-6 0.6252 0.5230 0.3088 0.4387
q-7 0.6270 0.6484 0.1 107 0.3165
q-8 0.6914 0.4344 0.2278 0.3969
q-9 0.6885 0.4615 0.2247 0.3638
q- 10 0.6569 0.4762 0.2980 0.3 181
VERDE-"00604 """""" 5 .032'5'""""'000’165 """"" 0 '62’6’2’

a Normal mortality estimate based on 100 observations per sampling date.
b J acknife mortality estimates based on 80 observations per sampling date.
C Jacknife variance .

d J acknife variance estimate based on 9 subsamples.

83

Table 15. Comparison between the common and the Jacknife estimate of the

stage-specific mortality rate using Southwood's method.

STAGE MORTALITY WITHIN THE STAGE
1987 aNFIDEvCE INTERVAL 1988 cavaEvc‘E INTENAL

EGGS 0.62918 0.6465

0.7151b : 0.2073c 0.5947 : 0.0649
FIRST 0.3640 0.5259
INSTARS 0.2056 : 0.4045(1 0.6200 : 0.1645
SECOND 0.4166 0.2409
INSTARS 0.4058 : 0.2534d 0.0757 : 0.2880d
THIRD 0.2776 0.3723
INSTARS 0.2638 : 0.1664 0.4233 : 0.1 158

a Mortality calculated in the usual way with the Southwood's method. All the
observations were considered for the mortality estimate (100 observations per
sampling date).

b Jacknife mortality estimation based on 80 observations per sampling date.

c Jacknife confidence interval. 19, ajfa = 0,05,

d Jacknife confidence interval. t 3, alfa = 0,05,

 

A 80 -

a":

Z 70 - .

<

m 1

E 60 -

N

o 50

E —I-— L-1
—-o— EGGS

11.) 4° —I— L-4

d

'0', 30

0 510152025303540
DATA POINTS TAKEN AT ONCE

Figure 18. Relationship between the size of the subsamme removed and the
variability of the sampling data of the Colorado potato beetle on

horsenettle.

m“,-
_ 0

 

LITERATURE CITED

Drummond, F. A. 1988. Methods in ecological statistics. Michigan State University,
East Lansing. Not published

Groden, E. 1988. Studies in the natural mortality of the Colorado potato beetle.
Leptinotarsa decemlineata (Say). Ph.D. dissertation. Michigan State

University, East Lansing.

Groden. E. and R A. Casagrande. 1986. Population dynamics of the Colorado potato
beetle. Leptinotarsa decenilineata (Coleoptera : Chrysomelidae) on Solanum
berthaulii . J. Econ. Entomol. 79: 91-97.

Helgesen. R G. and D. L. Haynes. 1972. Population dynamics of the cereal leaf beetle.
Otdema melanopus (Coleoptera : Chrysomelidae): a model for age
specific mortality. Can. Entomol. 104: 797-814

Logan. P. A. 1981. Estimating and projecting Colorado potato beetle density and potato
yield loss. In J. H. Lashomb and R A. Casagrande (eds). Advances in potato pest
management. Hutchinson & Ross Publishing Co.. Stroudsburg. PA. pp 105-1 18.

Logan. P. A. and R A. Casagrande. 1980. Predicting Colorado potato beetle (Leptinotarsa
decemlineata Say) density and potato yields loss. Environ. Entomol. 9:
659-663.

Logan. P. A.. R A. Casagrande, H. H. Faubert. F. A. Drummond. 1985. Temperature-
dependent development and feeding of immature Colorado potato beetle
Leptinotarsa decemlineata (Say) (Coleoptera : Chrysomelidae). Environ.
Entomol. 14:275-283.

Manly , B. F. J. 1974. A comparison of methods for the analysis of insect stage-
frequency data. Oecologia 17: 335-348.

Manly. B. F. J. 1977. A further note on Kiritani and Nakasuji's model for stage-
frequency data incluiding comments on the use of Tukey's jacknife
technique for estimating variances. Res. Pop. Ecol. 18: 177-186.

Manly. B. F. J. 1979. A note on key factor analysis. Res. Pop. Ecol. 2 1(1): 30-39.

Miller. R G. 1974. The jacknife- a review. Biometrika 61(1): 1-15.

Mills. N. J. 1981. The estimation of recruitment from stage frequency data. Oecologia
51: 212-216.

Mosteller, F. and J. W. Tukey. 1977. Data analysis and regression-a second course in
statistics. Addison-Wesley. Reading. Massachusetts.

86

Quenouille. M. H. 1949. Approximate tests of correlation in time-series. J. R Statist.
Soc. B 1 1:68-84

Quenouille. M. H. 1956. Notes on bias in estimation. Biometrika 43: 353-360.
Sawyer. A. J. and D. L. Haynes. 1984. On the nature of errors involved in estimating
stage-specific survival rates by Southwood's method for a population

with overlapping stages. Res. Pop. Ecol. 26: 331-351.

Southwood. T. R E. 1978. Ecological methods with particular reference to the study of
insect populations. 2 ed. Wiley. New York.

. J. W. 1958. Bias and confidence in not quite large samples. Ann. Math. Statist.
29: 614

 

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