M7 9 ‘5" ’ " mullTimnummulmulmmm

293 00625 1908

 

 

 

 

 

 

 

 

 

 

 

 

 

 

LIBRARY '—
Michigan State
University

 

 

I

 

This is to certify that the
dissertation entitled
The Relationship of Chinch Bug (Blissus leucogterus

Hemiptera:Lygaeidae) Presence and Abundance to
Parameters of the Turfgrass Environment

 

presented by

Maria Geraldine Davis

has been accepted towards fulfillment
of the requirements for

Ph- D- degree in Entomology

 

/'K

/ x f

/

Q}: /«M/u</ mw

Major WW ;/

,I'

Dam August 3, 1989 //

 

MSU is an Affirmative Action/Equal Opportunity Instilution 0-12771

 

 

PLACE IN RETURN BOX to remove this checkout from your record.
TO AVOID FINES return on or before date due.

DATE DUE DATE DUE DATE DUE
°2 51%

 

 

 

 

 

 

 

 

 

 

 

 

 

 

MSU Is An Affirmative Action/Equal Opportunity Institution

 

THE RELATIONSHIP OF CHINCH BUG (BLISSUS LEUCOPTERUS
HEMIPTERAzLYGAEIDAE) PRESENCE AND ABUNDANCE TO
PARANIETERS OF THE TURFGRASS ENVIRONMENT

By

Maria Geraldine Davis

A DISSERTATION

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

DOCTOR OF PHILOSOPHY

Department of Entomology

1989

booISSX

.fa‘ELLE ._ .. .

ABSTRACT

THE RELATIONSHIP OF CHINCH BUG (BLISSUS LEUCOPTERUS
HEMIPTERAzLYGAEIDAE) PRESENCE AND ABUNDAN CE TO
PARAMETERS OF THE TURFGRASS ENVIRONMENT

By

Maria Geraldine Davis

Selected parameters of the chinch bug (B_1iwsleuggpteru§) turfgrass
environment were examined over a three year period in a survey of 108 home
lawns in the greater Lansing area of Michigan. Variables included were
thatch thickness, grass height, dry weight of the grass, chlorophyll content,
thatch and ambient temperature, soil moisture, and species composition of the
lawn. Numbers of chinch bug and predaceous arthropod were counted using
a transect sampling method. Thatch thickness was positively correlated to
the abundance of chinch bugs in all three years. It was the only variable that
was significantly correlated to chinch bug abundance in all three years. In
field experiments thick thatch was induced by applications of the fungicide
mancozeb, and chinch bug populations increased. In lawn surveys, thatch
grew thicker over a two year period in chinch bug infested lawns, but did not
change in non-infested ones. Chinch bugs released into thatchy and
dethatched areas appeared to have at least a short-term habitat preference for
thatchy turf. Big-eyed bugs (Gegcgris bullatus Say) were observed to feed
on adult chinch bugs in the laboratory, but confinement with big-eyed bugs

 

did not significantly affect chinch bug population sizes in the laboratory.
There was significantly more fine fescue (Efestuca rubra) and less
Kentucky bluegrass (Boa pratensis) in infested lawns as compared with

 

 

Maria Geraldine Davis
non-infested lawns. A linear discriminant function was determined for
1986 data using percent Kentucky bluegrass and thatch thickness as the
variables of interest. When tested using data from 1986, 1987, and 1988
the function correctly predicted chinch bug presence in lawns between 63
and 81 percent of the time. In the laboratory, chinch bugs were found to
feed more on Kentucky bluegrass than on fine fescue. There was a
tendency for chinch bugs to hide in Kentucky bluegrass preferentially over

fine fescue, although the difference was not significant.

To Terry

iv

ACKNOWLEDGEMENTS

I thank my major professor, Dr. David Smitley, for his support and
encouragement throughout my graduate work.

I thank the members of my committee, Dr. Fred Stehr, Dr. William
Mattson, Dr. Joseph Vargas J r., and Dr. Jean Stout for their helpful
criticisms. A special thanks to Jean Stout for her input on papers for
publication.

I am grateful to Rebecca Allen, Kim Keams, Michele Eodchick, and
Mike Zupin for their generally enthusiastic help with my fieldwork. I
am donating a pair of knee-pads to the lab in their names.

Many thanks to the fourth floor gang for keeping things light-
hearted and fun during the past four years. It has been interesting
sharing an office with "The King" reincamate.

I thank Dr. Robert Graves for sparking my interest in insects, Dr.
Mimi Sayed and Dr. Howard Hagerman for their support of my
teaching endeavors, and my parents Herbert and Rita Kortier for all
they have done.

Finally, a great big thank you to my very special friend and
husband, Terry Davis, whose unfailing love and support have made

' the completion of this degree possible.

TABLE OF CONTENTS

LIST OF TABLES ............................................................ viii
LIST OF FIGURES ............................................................ ix

GENERAL INTRODUCTION AND
LITERATURE REVIEW ....................................................... 1

CHAPTER 1. Relationship of chinch bug (_Blissus leucopterus
HemipterazLygaeidae) abundance to parameters of

the turfgrass environment ................................... 11
Introduction .................................................. 12
Materials and Methods ....................................... 13
1986 Survey ......................................... 13
1987 Survey ......................................... 15
1988 Survey ......................................... .16
Results ......................................................... 16
Discussion .................................................... 28
Literature Cited ............................................... 31

CHAPTER 2. Influence of Thatch Layer on Populations of Chinch
Bugs (Blissus leucopterus HemipterazLygaeidae)

in Turfgrass ................................................... 33
Introduction ................................................... 34
Materials and Methods ...................................... 35
Induced Thatch Experiment ......................... 35
Dethatching Experiment ............................ .36
Predation Experiment ............................... 37
Survey ................................................ 38

vi

Results ........................................................ .38

Induced Thatch Experiment ........................ .38
Dethatching Experiment ............................. 4 2
Predation Experiment...............................42
Survey ................................................ 46
Discussion .................................................... 46
Literature cited ................................................ 50

CHAPTER 3. Feeding Preference of Chinch Bug (l_31issus leucopterus
HemipterazLygaeidae) for Fine Fescue and Kentucky

Bluegrass ..................................................... 52
Introduction ................................................... 53

Materials and Methods ...................................... 53

Resting Habitat Preference ......................... 54

Feeding Preference Tests ........................... 54

Results ........................................................ 57

Discussion .................................................... 57

Literature Cited ............................................... 59
SUMMARY ..................................................................... 60
APPENDIX 1. Record of Deposition of Voucher Specimens ............ 62
APPENDIX 1.1 Voucher Specimen Data .................................. 63

vii

Table 1.

Table 2.

Table 3.

Table 4.

Table 5.

Table 6.

LIST OF TABLES

Correlation coefficients of lawn parameters in

1986.Probability of r is reported in parentheses. For chinch
bug abundance, n=28, for all other variables,

n=34 ................................................................ 18

Correlation coefficients of lawn parameters in 1987.
Probability of r is reported in parentheses. For chinch bug
abundance, n=22, for all other variables, n=27 ................. 19

Correlation coefficients of lawn parameters in 1988.
Probability of r is reported in parentheses. For chinch bug
abundance, n=14, for all other variables n=66 .................. 20

Coefficients of linear discriminant function. Values of

variables are multiplied by the appropriate coefficient and then
added to the constant. The calculation giving the larger

number is the predicted habitat type of the lawn in question,
either chinch bug habitat (INF) or not chinch bug habitat

(N ON ) ................................................................ 23

Computer classifications of infested (INF) and non-infested
(NON) lawns using percent Kentucky bluegrass and thatch
thickness variables. Data from 1986 were used to calculate

the initial discriminant function. Data from 1987 and 1988

are independent tests of the function. Underlined values are
percent correct classification for each group ..................... 24

Mean number of chinch bugs observed in thatched and
dethatched turfgrass plots. Variance is reported in
parentheses ........................................................... 43

viii'

 

Figure 1.

Figure 2.

Figure 3.

Figure 4.

LIST OF FIGURES

Average proportion of chinch bug infested (inf) and non-
infested (non) lawns composed of Kentucky bluegrass, fine
fescue, and other plants 21

 

Plot of thatch thickness and species composition data from

1986 showing relative relationship to discriminant function

line. Points falling below the line are classified by the function

as chinch bug habitats (INF). Those above the line are

classified as non-chinch bug habitats (NON). Sixty-three

percent of the non-infested lawns are correctly classified (i.e.

fall above the line) as are 78% of the infested lawns (i.e. fall
below the line) ........................................................ 25

Plot of thatch thickness and species composition data from

1987 showing relative relationship to discriminant function

line. Points falling below the line are classified by the function

as chinch bug habitats (INF). Those above the line are

classified as non-chinch bug habitats (NON). Seventy-five
percent of the non-infested lawns are correctly classified (i.e.

fall above the line) as are 81% of the infested lawns (i.e. fall
below the line) ......................................................... 26

Plot of thatch thickness and species compostion data from

1988 showing relative relationship to discriminant function

line. Points falling below the line are classified by the function

as chinch bug habitats (INF). Those above the line are

classified as non-chinch bug habitats (NON). Seventy -one
percent of the non-infested lawns are correctly classified (i.e.

fall above the line) as are 64% of the infested lawns (i.e. fall
below the line) ........................................................ 27

 

Figure 5.

Figure 6.

Figure 7.

Figure 8.

Figure 9.

Cumulative number of chinch bugs in control and mancozeb
treated plots in 1986. Data are sums of average number of

bugs observed in 3720 cm2 in each of 4 plots. Slopes of lines
are significantly different (control: m=.0665, mancozeb:
m=.137, t=2.51, df=10 .02<P<.05) 39

 

Cumulative number of chinch bugs in control and dithane

treated plots in 1987. Data are sums of average number of

bugs observed in 6 transects in each of 7 plots. Slopes of lines
are significantly different (Control:m=.094, mancozeb:m=.l86,
t=7.40, df=26, P<<.001). Vertical bars represent peak density
of instar groups, determined as the 50% point in the cumulative
instar group count. N1+2 means the group of nymphal instars

1 and 2, etc. and A stands for adult 40

 

Number of chinch bugs surviving one week confinement with
different numbers of big-eyed bugs (BEB), first experiment.

Due to mortality of BBB during the experiment, BEB numbers
are reported as the average live BEB. Slopes and intercepts of
lines are not significantly different (slope of non-thatch

treatment =l.41, thatch treatment=l.56, t=1.195, P>.05; for

test of intercepts, t=0.322, P>.05 44

 

Number of chinch bugs surviving one week confinement with
different numbers of big-eyed bugs (BEB), second experiment.
Due to mortality of BBB during the experiment, BEB numbers
are reported as the average live BEB. Slopes and intercepts are
not significantly different 45

 

Choice chamber used in feeding preference test. The chamber
consisted of a modified 90 mm plastic Petri dish. One fine

fescue and one Kentucky bluegrass plant were held upright in
moist white silica sand ’ 56

 

 

GENERAL INTRODUCTION

The chinch bug, Eggs leugopterus Montandon (HemipterazLygaeidae),
is a native North American insect that has become a major pest of turfgrass.
In 1985, Michigan lawn care companies reported it to be the number one
turfgrass pest (D. R. Smitley, pers. comm.) Although insecticides provide
the major means of control (Niemczyk, 1984), cultural management may be
more practical and desirable for urban turf. Reduction of pesticide input may
not only reduce human health hazards, but also ameliorate stressed predator
or pathogen populations, thus allowing natural enemies to play a role in
control of the chinch bug (Knipling, 1979; Tashiro, 1987). Moreover,
changes in cultural practices may present a long term solution to outbreaks
rather than short term control (Knipling, 1979). A better understanding of the
factors that regulate population growth and decline of an insect is the first step

in the development of an effective cultural control (Knipling, 1979).

LITERATURE REVIEW

Four species of the genus Blissus are known in North America:

 

leuggpterus, insularis, arenarius, and maritimus (Leonard, 1966), but only
_B_. leuggpterus and B. insularis are considered economically important. Two

subspecies of B. leucopterus, _B_. I. hirtus and B. I. leucopterus, differ slightly
1

2

in morphology, geographic distribution, host preference, and habitat
preference, but readily interbreed. It is fruitless to assign a subspecies name

where the ranges of the two overlap (Leonard, 1966). Blissus leucopterus

 

hirtus, or the "hairy" chinch bug, typically feeds on northern cool season
turfgrasses, whereas 11.1. leucopterus generally feeds on grains, such as
wheat, corn and sorghum. The range of B. 1. hirtus spans a triangle from

Minnesota, to Virginia, to Maine. Blissus leucopterus leucopterus has a

 

distribution south of 11.1. hirtus, and west to Nebraska, Kansas, Oklahoma,
and Texas, although the two have a large area of overlap in Michigan. The

southernmost portion of the United States is inhabited by B. insularis, a pest

 

of the warm-season turfgrasses (Leonard, 1966).

The first record of damage by the chinch bug in North America dates to
1783 in North Carolina, when the insect nearly destroyed the wheat crop
there (Fitch, 1856). The species Blissus leucopterus was first described in

 

North America by Say in 1831 from a specimen collected on the coast of
Virginia. The insect was established as a pest of grains in the Midwest,
however widespread damage did not occur until 1864 when grainlosses in
Illinois were estimated at 73 million dollars (Leonard, 1966). _Iflssls

leucopterus hirtus was first described as a species, B. hirtus, by Montandon

 

(1893) and later given subspecies status by Leonard (1966). Heavy
infestations of I_3_. I. hirtus in lawns and golf courses was first reported on

Long Island, New York, in 1932 (Maxwell and MacLeod, 1936). ~

The chinch bug overwinters as an adult, usually in tufts of grass or under

 

plant debris, and often around the foundations of buildings (Leonard, 1966).
Diapause is apparently photoperiod induced, with short day length inhibiting
mating and feeding behavior (Smith et al., 1981). The bugs become active in
the spring when temperatures rise above 7°C (Liu and McEwen, 1979). Eggs

 

are laid in April or May, depending on the latitude. The species is bivoltine in
Ohio (Martin, 1976) but may be univoltine in some northern areas
(Niemczyk, 1984).

There is some confusion over the base temperature for development of the
insect. Liu and McEwen (1979) calculated the base temperature for
development to be 7°C. They dissected females kept at various temperatures
and determined the minimum temperature for egg development in the ovaries.
Mailloux and Streu (1981) determined the base temperature to be 14.6°C.
They determined this from observation of development of eggs kept at
different temperatures. None of the authors observed the effect of
temperature on the development of immature stages. Seven degrees
centigrade is taken to be the activity threshhold by most authors
(Kennedy,1981;Tashiro, 1987). In this dissertation, 146°C is the base
temperature used in degree day calculations for development. Approximately
122 degree-days (base 14.6°C) is the minimum for completion of egg
development (Mailloux and Streu, 1981).

The insect passes through five nymphal stages (Mailloux and Streu, 1981)
and it is these stages that cause the most lawn damage (Duble and N iemczyk,
1979). The early instars are bright red with a white stripe across the
abdomen. The later instars become progressively darker, with the fifth instar
being a dark brownish black. Development of wing pads increasingly
obscures the white stripe in later instars. A taxonomic key that uses head
width to distinguish among the nymphal instars appears in Mailloux and
Streu (1981). The adult chinch bug is approximately 4.5 mm long, with a
black body and yellow legs; the hemelytra are milky-white. In B. I.
leucopterus, the setae covering the head are silver-gray , whereas they are
straw-yellow in _B_. I. hirtus (Leonard,l968).

 

 

The first instar was found to reach peak population size at 176 degree days
and the second instar at 236 degree days(base 14.6°C, Mailloux and Streu,
1981). The number of third and fourth instars, lumped together owing to
difficulty in differentiating between them in the field, was found to peak at
334 degree days. Fifth instars peaked at 501 and adults at 637 degree days
(Mailloux and Streu, 1981).

The chinch bug feeds by inserting its proboscis into the vascular tissue of
a plant and sucking out the sap. The saliva may be toxic to the plant. Feeding
damage clogs the plant's conductive tissues, preventing water and nutrients
from reaching leaves and new shoots. Prolonged feeding may eventually kill
the plant. The damage usually appears as scattered patches in open sunny
areas of the lawn which become yellow and brown as the turf dies (Martin,
1976).

Most of the cool season turfgrasses are fed upon by the hairy chinch bug,
including the two most common, fine fescue (Fe_s_tu_c_a _rulxa) and Kentucky
bluegrass (Eo_a pratensis)(L_eonard, 1966, Tashiro, 1987). Other cool-season
grasses that serve as hosts are perennial ryegrass (Elm. p§_r_e_nge) and
bentgrasses (Agrostis sp.)(Baker et al., 1981a). Leonard (1966) states that
bentgrasses are preferred, but gives no empirical evidence. Some feeding
preferences for cultivars within grass species are known (Ratcliffe, 1982),
but between species preferences are not. Crabgrass (Digitaria sp.) is usually
avoided, and is often left undamaged in an otherwise decimated lawn
(Leonard, 1966). Significant differences in tolerance to feeding exist among
Kentucky bluegrass cultivars (Baker et al., 1981b). Ahmad et al. (1984)
report that Kentucky bluegrass does not serve as a host for B. l. leucopterus
in Nebraska; this is consistent with its status as a pest of grain crops, not of

turfgrass.

 

It is not clear. why chinch bug outbreaks do not occur in all lawns. Four
groups of variables which may be important in regulating chinch bug
population density are discussed in the literature. These. are 1) grass species,
2) lawn health, 3) cultural practices, and 4) natural enemies.

The species of grass present may be an important factor in whether or not
a lawn becomes infested. Non-native grass species in Kansas (such as the
cool-season turfgrasses) have been shown to be more susceptible to chinch
bug attack than indigenous species (Hayes and Johnson, 1925). Differences
in tolerance of cultivars of turfgrasses to chinch bug feeding have been
identified and may explain discrepancies in host range descriptions (Ratcliffe,
1982). Antibiosis has been shown in some cultivars of Kentucky bluegrass
(Ahmad et al., 1984). Ramoska and Todd (1985) demonstrated a reduced
infectivity rate by the insect pathogenic fungus Beauveria bassiana when_B, L
leucopterus was fed on corn or sorghum, as compared to bugs fed on barley,
wheat, artificial diet, or water alone. Efficacy of pathogens may also differ
for _B. I. h_ir_ms_ depending on host plant.

The health of the lawn may play a role in chinch bug attack. The chinch
bug is commonly described as a dry weather insect, being most often
reported in abundance in hot dry years (Flint et al., 1935; Mailloux and Streu,
1981; Schread, 1970). Guthrie and Decker (1954) found that dry weather
favors longevity if food is available. The greatest injury to turf occurs during
July and August, when it is drought stressed (Duble and Niemczyk, 1979).
However, it is not clear from the literature whether drought-stressed lawns
are attractive to the chinch bug, conducive to population growth, or whether
damage is simply more apparent on these lawns.

Turf cultural practices may influence the susceptibility of a lawn to chinch
bug damage. One way this is possible is through pesticide-induced

suppression of natural enemies. Hairy chinch bug p0pulations were shown
to increase following several years of treatment with chlordane (Streu and
Cruz, 1972; Streu and Vasvary, 1966). The southern chinch bug, Blissus

insularis, is known to be resistant to organophosphate pesticides in Florida

 

 

(Reinert and Portier, 1983). An increase in B. l_. 11% numbers in chlordane
treated plots was more likely to have been caused by reduced chinch bug
predator pressure, as chinch bug population increases were correlated with
reductions in predaceous mite species (Streu, 1973), but a direct cause and
effect was not established. In general, insecticide applications have been
shown to greatly reduce predaceous arthropod populations in turf (Cockfield
and Potter, 1983). Fungicides have also been shown to eliminate naturally
occurring insect pathogenic fungi on potatoes (Loria et al., 1983); they may
have similar impact in turfgrass.

Various components in fertilizer used in turf culture may also influence
susceptibility of a lawn to damage. Sorghum resistance to chinch bug attack
was substantially reduced by treatment with sodium nitrate but its resistance
was significantly increased by treatment with phosphate (Dahms and Fenton,
1940).

Several biotic factors have been determined to be important in chinch bug
population regulation. Five egg mortality factors have been identified, which
result in a 48% reduction in population size The five factors are: 1)
Eumicrosoma beneficum Gahan, a hymenopteran parasite (Scelionidae ), 2)

Amara sp. (Carabidae) which preys on eggs, 3) desiccation, 4) an

 

undescribed fungal disease, and 5) failure to hatch due to unknown causes
(Mailloux and Streu, 1981).
Factors causing mortality of nymphs and adults are not as well defined.

Wet thatch causes mortality of the first instars during eclosion (Mailloux and

 

Streu, 1981). Although chinch bug predators were shown by Mailloux and
Streu (1981) not to have an important effect, other authors (Cruz, 1972;
Niemczyk, 1984) have identified the big-eyed bug, Geocoris bullatus, as an

 

important predator. At present no empirical evidence has been published.
Leonard (1966) points out that it is not known whether the big-eyed bug
actually preys on the chinch bug or whether they simply have similar habitat
preferences. Parasitoids have never been observed to emerge from nymphs
or adults (Mailloux and Streu, 1981).

The fungal pathogen Beauveria bassiana is a significant mortality factor,

 

reducing generation sizes by about 17% (Mailloux and Streu, 1981).
Ramoska (1984) found conidia to be invasive and pathogenic at all relative
humidities tested, although production of conidia only occurred in chinch
bugs incubated at 75% relative humidity or higher.

Winter mortality ranges between 28 and 68% in Metuchen New Jersey,
depending on the severity of the winter (Mailloux and Streu, 1981). Leonard
(1966) reports a winter mortality of 34% in Mansfield, Connecticut. Decker
and Andre (1936) showed that the ability of chinch bugs from Iowa to
withstand freezing temperatures is relatively low. Minimum temperatures
recorded in the northern half of the United States should be sufficient to cause
100% mortality. They suggest that the insulation provided by dead grass,
leaves, and snow cover is essential to the over-wintering survival of the

chinch bug.

 

LITERATURE CITED

Ahmad, T. R., K. P. Pruess, and S. D. Kindler. 1984. Non-crop grasses
as hosts for the chinch bug, Blissus lemma W
(Say)(I-Iemiptera: Lygaeidae). J. Kansas Ent. Soc. 57:17-20.

Baker, P. B., R. H. Ratcliffe, and A. L. Steinhauer. 1981a. Laboratory
rearing of the hairy chinch bug. Environ. Entomol. 10:226-229.

Baker, P. B., R. H. Ratcliffe, and A. L. Steinhauer. 1981b. Tolerance to
hairy chinch bug feeding in Kentucky bluegrass. Environ. Entomol.
10:153-157.

Cockfield, S. D. and D. A. Potter. 1983. Short-tenn effects of insecticidal
applications on predaceous arthropods and oribatid mites in Kentucky
bluegrass turf. Environ. Entomol. 12:1260-1264.

Cruz, C. 1972. Chlordane effects on the hairy chinch bug ecology. Part 1.
EffeCt on population dynamics and predators. Part 2. Effect on
turfgrass habitats and organisms. Ph. D. Thesis, Rutgers--The State
University of New Jersey. 115 pp.

Dahms, R. G. and F. A. Fenton. 1940. The effect of fertilizers on chinch
bug resistance in sorghums. J. Econ. Ent. 33:688-692.

Decker, G. C. and F. Andre. 1936. Studies on temperature and moisture as
factors influencing winter mortality in adult chinch bugs.

Duble, R. L. and H. D. Niemczyk. 1979. Insects: Once a nuisance, today a
problem. Turfgrass Times, March/April:12-23.

Fitch, A. 1856. Chinch bug. Trans. N. Y. State Agr. Soc. 15:277-297.

Flint, W. P., G. H. Dungan, and J. H. Bigger. 1935. Fighting the chinch
bug on Illinois farms. Agric. Expt. Cir. Univ. Ill. 431:1-16.

Guthrie, F. E. and G. C. Decker. 1953. The effect of humidity and other
factors on the upper thermal death point of the chinch bug. J. Econ.
Ent. 47:882-887.

 

 

9

Hayes, W. P. and C. 0. Johnson. 1925. The reaction of certain grasses to
chinch bug attack. J. Agric. Res. 31:575-583.

Kennedy, M. K. 1981. Chinch bugs: biology and control. American
Lawnapplicator, August, pp. 12-15.

Knipling, E. F. 1979. The basic principles of insect population suppression
and management. U. S. D. A. Agriculture Handbook No. 512. 623
PP-

Leonard, D. E. 1966. Biosystematics of the "W complex" of the
genus Blissus. Conn. Ag. Exp. Bull. 677, pp. 1-45.

 

 

Leonard, D. E. 1968. A revision of the genus Blissus (Heteroptera:
Lygaeidae) in eastern North America. Ann. Ent. Soc. Am. 61:239-
250.

Liu, H. J. and F. L. McEwen. 1979. The use of temperature accumulations

and sequential sampling in predicting damaging populations of Blissus
leucopterus hirtus. Environ. Entomol. 8:512-515.

 

 

Loria, R., S. Galaini, and D. W. Roberts. 1983. Survival of the innoculum

of the entomopathogenic fungus Beauveria Bassjfla as influenced by
fungicides. Environ. Entomol. 12: 1724-1726.

Mailloux, G. and H. T. Streu. 1981 . Population biology of the hairy chinch

bug (Blissus W, MontandonzHemiptera:Lygaeidae). Ann.
Soc. Ent. Quebec 26:51-90.

Martin, D. P. 1976. Potential insect problems for Michigan in 46th Annual
Michigan Turfgrass Conference Proc., J. M. Vargas, Jr. ed.,5:55-56.

Maxwell, K. E. and G. F. MacLeod. 1936. Experimental studies of the
hairy chinch bug. J. Econ. Ent. 29339-343.

Montandon, A. L. 1893. Lygaeidae exotiques. Notes et description
d'especes nouvelles. Ann. Soc. Entomol. Belg. 37:399.

Niemczyk, 1984. Turf insect control guide. Weeds Trees, and Turf, May:
28-46. ‘

 

10

Ramoska, W. A. 1984. The influence of relative humidity on Beauveria
bassiana infectivity and replication in the chinch bug, Blissus
leucopterus. J. Invert. Pathol. 43:389-394.

 

Ramoska, W. A. and T. Todd. 1985. Variation in efficacy and viability of
Beauveria bassiana in the chinch bug (HemipterazLygaeidae) as a result
of feeding activity on selected host plants. Environ. Entomol. 14:146-
148.

Ratcliffe, R. H. 1982. Evaluation of cool-season turfgrasses for resistance
to the hairy chinch bug. pp. 13-18 in: Advances in Turfgrass
Entomology, H. D. Niemczyk and B. J. Joyner, eds., Hammer
Graphics, Piqua, OH., 150 pp.

Reinert, J. A. and K. M. Portier. 1983. Distribution and characterization of
organophosphate-resistant sourthem chinch bugs (Heteroptera:
Lygaeidae) in Florida. J. Econ. Ent. 76:1187-1190.

Schread, J. C. 1970. Chinch bug control. Conn. Agric Expt. Sta. Cir.
233:1-6.

Smith, M. T., G. Wilde, and T. Mize. 1981. Chinch bug: Damage and
effects of host plant and photoperiod. Environ. Entomol. 10:122-124.

Smitley, D. R. 1985. Dept. of Entomology, Michigan State University, East
Lansing, MI 48824.

Streu, H. T. 1973. The turfgrass ecosystem: impact of pesticides. Bull.
Entomol. Soc. Am. 19:89-91.

Streu, H. T. and C. Cruz. 1972. Control of the hairy chinch bug in
turfgrass in the northeast with Dursban insecticide. Down to Earth
2821-4.

Streu, H. T. and L. M. Vasvary. 1966. 1966 report of turfgrass research.
Rutgers University, pp. 78-82.

Tashiro, H. 1987. Turfgrass insects of the United States and Canada.
Cornell University Press. Ithaca, N. Y. 391 pp.

 

CHAPTER 1

Relationship of Chinch Bug (Blissus leucopterus HemipterazLygaeidae)

Abundance to Parameters of the Turfgrass Environment.

 

INTRODUCTION

The chinch bug, Blissus leucopterus Montandon (HemipterazLygaeidae), a

 

native of North America, is a major pest of the imported cool-season
turfgrasses (Tashiro, 1987). Although insecticides provide the usual means
of control (N iemczyk, 1984), alternative management strategies are more
desirable, given the increased concern over pesticide use in the urban
environment. If the LD50 is used as an indicator of health risk, insecticides
could be targeted by environmental action groups because insecticide LD50's
are generally lower than those of herbicides, fungicides, or of fertilizers used
on turfgrass (Anonymous, 1986). In addition to environmental and health
concerns, home lawn insecticide applications may also be undesirable owing
to their broad spectrum toxicicological effects on predaceous arthropods that
normally regulate populations of chinch bugs and other turfgrass insect pests
(Cockfield and Potter, 1985; Knipling, 1979; Reinert and Portier, 1983;
Tashiro, 1987). Moreover, practical cultural management strategies are more
desirable, as they present long term solutions rather than short term controls
for outbreaks (Knipling, 1979).

Reliable cultural control practices cannot be developed until more is
learned about the probable causes of chinch bug outbreaks in home lawns.
Cultivar susceptibility, predator suppression and moisture stress have been
suggested as likely factors causing chinch bug outbreaks. Cultivar selection
could be an important factor. Kentucky bluegrass cultivars differ
significantly in susceptibility to chinch bug damage (Ratcliffe, 1982; Baker et
al., 1981). Field populations of chinch-bugs were affected differentially by

cultivars of perennial ryegrass, although survival rates on these cultivars did

12

13

not differ (Ratcliffe, 1982). Predator suppression may also be a factor.
Lawns with high fertilizer and pesticide input have fewer predators
(Cockfield and Potter, 1985) and a higher probability of having chinch bug
problems (Duble and Niemczyk, 1979). Thatch has been noted as being a
significant factor for populations of the southern chinch bug, @113 must—rig
(Reinert and Kerr, 1973), but there is no evidence as to how thatch affects the
species. Niemczyk (1984) hypothesized that chinch bug injury is more likely
during periods of moisture stress. Irrigation or rainfall may also suppress
chinch bug numbers below damaging levels (Duble and N iemczyk, 1979).
Unfortunately, experimental data supporting drought stress, predator
suppression, and thatch as factors influencing hairy chinch bug outbreaks are
lacking.

In this investigation I sought to describe the relationship between home
lawn characteristics and chinch bug infestations through a survey of
randomly selected lawns in the greater Lansing, Michigan area. Data were
collected on chinch bug and predaceous arthropod populations, grass health
parameters including chlorophyll content and dry weight, and abiotic factors
including temperature of the microenvironment and soil moisture. Additional
lawn parameters included grass height, thatch thickness and species
composition of the lawns. The intent was to develop a database for
discriminating between favorable and unfavorable chinch bug habitats in the

turfgrass environment.

MATERIALS AND METHODS

1986 Survey. Home lawns in the Lansing Michigan area were selected by

requesting permission for the use of the lawns of the faculty and staff of

 

14

several departments in the College of Natural Science at Michigan State
University. Each of 126 lawns was sampled once for the presence of chinch
bugs with a ten minute visual inspection of the grass and thatch, during late
June or July. A lawn was determined to have a chinch bug population if one
or more chinch bugs were found. A total of 28 chinch bug infested lawns
were identified from the 126 lawns sampled. During the week of August 12
to August 19, 1986, several additional attributes were estimated by sampling
the 28 infested lawns as well as 16 randomly selected non-infested lawns.
Four types of information were collected from each lawn: arthropod
population densities, grass health parameters, abiotic parameters, and lawn
parameters.

1. Arthropod population densities--The grass, thatch, and exposed soil
were visually inspected for chinch bugs within a 1.5 m long, 2.5 cm wide
transect. The transect was defined by a loop of string stretched around two
one inch wide row markers placed five feet apart. Five randomly placed
transects per lawn were thoroughly searched, with search time varying
between three and five minutes, depending on the density of the grass.
Predaceous arthropods were also counted during this time. All sampling was
conducted between 9 AM and 7 PM.

2. Grass health parameters--Grass plant density and chlorophyll content
were measured as indicators of grass health. Grass density was estimated by
taking samples of grass with a 7.6 cm metal clip. When the clip was
squeezed open and allowed to close on grass blades it effectively collected all
blades in a 2.5 by 7.6 cm patch. The grass trapped in the clip was cut off at
soil level using scissors. This was repeated three times in each lawn. The
samples were dried at 60° C for 24 hours and then weighed. In this way the

dry weight of a standardized area of turf was measured.

15

Chlorophyll content of the grass was measured by suspending 0.25 g of
dried grass blades in methanol for 24 hr. Aliquots were analyzed with a
Beckman spectrophotometer as described by Johnson (1974).

3. Abiotic parameters--Stratified air temperature data and soil samples for
determining soil moisture were collected at each lawn. Air temperature was
measured at three levels, in the thatch layer, 15 cm and 1.2 m above thatch,
using a shaded thermometer. Five cm deep soil cores were taken with a 2.5
cm diameter cork borer and placed into pre-weighed vials. Vials with soil
were weighed and then dried at 60° C for 24 hours. After drying, they were
again weighed, allowing computation of percent soil moisture for three
samples per lawn.

4. Lawn parameters--Thatch thickness and grass height were measured to
the nearest mm at three randomly selected points in the lawn. Species
composition of the lawn was determined by removing one plant every 30 cm
along a 3 m long transect randomly placed in the lawn. The transect sample
was replicated five times, making a total of 50 plants sampled per lawn.
Grass and weed plants were placed in a plant press and samples were later
determined to species using Turgeon and Giles (1984 ). These data were

taken for only six of 16 non-infested lawns.

1987 Survey. Data from 27 infested lawns and 15 non-infested lawns were
collected in early July and again in late August to determine chinch bug
abundance, thatch thickness, grass height and grass species composition.
Most of the lawns intensively surveyed in 1986 were included again in the
1987 survey. For logistical reasons, seven of the non-infested lawns were
replaced with new non-infested lawns One of two infested lawns was

replaced for the same reason, the other had an insecticide treatment applied

16

by the homeowner. From 1986 to 1987, one infested lawn became non-
infested and one non-infested became infested. Only parameters that showed
a relationship to chinch bug abundance in 1986 based on a correlation
analysis (SAS Institute, 1985) were used again in 1987. These were thatch
thickness, grass height, and lawn composition. Thatch thickness and grass
height were measured to the nearest mm at five random points in the lawn on
both sampling dates. Lawnspecies composition was determined as in 1986.

1988 Survey. A new set of lawns was identified for use in validating a
discriminant function determined from the 1986 data. Streets in the Lansing
area were selected from map listings using a random number generator.
Potential study lawns on each selected street were also randomly selected. Of
112 homeowners that were approached, 66 responded favorably to inclusion
of their lawn in this study. Of those 66 lawns, 14 were found to have chinch
bugs. Chinch bug abundance, thatch thickness, grass height and species
abundance were determined as previously described. Survey was conducted
from July 22 to August 10, 1988.

Data analysis. Data were analyzed using Statistical Analysis Systems
(SAS Institute, Inc., 1985). All percentage data were are sin square root
transformed before analysis. Discriminant analyses were done with prior
probabilities proportional. A discriminant function was written using the
1986 data and was used to test the 1987 and 1988 data. Five leave-five-out
jackknife tests of the 1986 data were done (Sokal and Rohlf,198l).

RESULTS

Of all the variables surveyed in 1986, only thatch thickness and grass

height were found to be significantly correlated with chinch bug abundance

 

17

(r= 0.444, p=0.023, and $0.563, p=0.003, respectively, Table 1). These
variables were also significantly correlated with each other (r= 0.622,
p=0.0001, Table 1). In 1987 thatch thickness was again significantly
correlated to chinch bug abundance (r=0.429, p=.025, Table 2) but grass
height was not (r=-0.176, p=0.379, Table 2). Thatch thickness and grass
height were not correlated with each other in that year (r= 0.266, p=0.l79).
Again in 1988, thatch thickness was the only variable significantly correlated
with chinch bug abundance (#0252 P=0.041, Table 3).

In all three years, percent fine fescue (Em ru_br_a) and percent Kentucky
bluegrass (BCE pratensis) were significantly negatively correlated (Tables 1, 2
and 3). Kentucky bluegrass and fine fescue were the most commonly
occurring turfgrasses, with Kentucky bluegrass occurring in 98% of all lawns
sampled and fine fescue occurring in 79%. Chlorophyll content of the grass
was positively correlated to soil moisture and to grass height (r=0.414,
p=0.015, and r=0.467, p=0.005, respectively, Table 1).

When lawns were classified as infested or non-infested, significant
differences were found in the thatch thickness and species composition.
Thatch was significantly thicker in lawns infested with chinch bugs. Infested
lawns had an average of 8.9 mm thatch whereas non-infested averaged 5.1
mm (t=3.52, 0.001<P<0.002). Lawns that had chinch bugs had more fine
fescue and less Kentucky bluegrass than lawns'that did not have chinch bugs
(Figure 1). Infested lawns had an average fine fescue composition of 35%,
compared to 12% in non-infested lawns (t=5.31, P<0.0001). Infested
lawns had an average Kentucky bluegrass composition of 42%, compared to
62% in non-infested lawns (t=4.12, P< .0001). Proportions of other grass
and weed species, either considered separately or as one group, were not

significantly different between infested and non-infested lawns.

 

18

Table 1. Correlation coefficients of lawn parameters in 1986. Probability of
r is reported in parentheses. For chinch bug abundance, n=28, for all other
variables, n=34.

 

 

moisture T 0 pkb ptf ght dwt chl tth prd

Temperature at 0" .147 -
(T 0) (.405)

Percent Kentucky .148 -.0160 -
bluegrass (pkb) (.402) (.926)

Percent fine fescue .066 .073 -.548 -

(pff) (.711) (.682) (.000)‘
Grass height .254 -.019 .104 .050 -
(ght) (.146) (.916) (.560) (.780)
Dry weight .045 -.130 .082 .102 .334 -
(dwt) (.800) (.463) (.643) (.564) (.054)
Chlorophyll content .414 -.259 .296 -.336 .467 -.008 -
(chl) (.015)‘ (.139) (.088) (.052) (.005)‘ (.965)

Thatch thickness .281 .108 .026 -.070 .622 .098 .191 -
(tth) (.107) (.544) (.882) (.693) (.000)‘ (.582) (.279)
Predators .233 -.008 .203 -.245 .228 .009 .107 .398

(prd) (.233) (.969) (.245) (.156) (.243) (.964) (.587) (.036)‘

Chinch bug abundance .312 .227 .064 .063 .563 -.004 .136 .444 .151
(.121) (.264) (.756) (.760) (.003)‘ (.986) (.508) (.023)‘ (.444)

 

19

Table 2. Correlation coefficients of lawn parameters in 1987. Probability of
r is reported in parentheses. For chinch bug abundance, n=22, for all other
variables, n=27.

 

 

pkb pff ght tth

Percent Kentucky -
bluegrass (pkb)

Percent fine fescue -.763 -

(P17) (-0001)'
Grass height .282 -.061 -
(ght) (154) (.762)

Thatch thickness .266 -.002 .266 -
(tth) (.180) (.992) (.179)

Chinch bug abundance-.108 .301 -.176 .429
(.591) (.127) (.379) (.025)‘

 

20

Table 3. Correlation coefficients of lawn parameters in 1988. Probability of r
is reported in parentheses. For chinch bug abundance, n=14, for all other
variables n=66.

 

 

pkb pff ght tth

Percent Kentucky
bluegrass (pkb)

Percent fine fescue -.512 -

(W) (.00011'
Grass height -.084 .098 -
(ght) (.503) (.435)

Thatch thickness .122 -.038 .152
(tth) (.329) (.759) (.223)

Chinch bug abundance.150 -.026 .173 .252
(.227) (.834) (.166) (.041)‘

 

 

Average Proportion

Figure 1.

21

 

 

1.0 -
other
0.8 -
fine fescue
0.6 -
0.4 -
0,2 - Kentucky bluegrass
0.0 -
non inf
Lawn Type

Average proportion of chinch bug infested (inf) and non-infested
(non) lawns composed of Kentucky bluegrass, fine fescue, and
other plants. '

22

Thatch thickness and species composition data were analyzed with a
discriminant function. The function is a vector with coefficients for the lawn
variables being analyzed. Coefficients for parameters of the function are
listed in Table 4. The values for the variables were multiplied by the NON
coefficients and then added to the NON constant for a non-infested .
computation and multiplied by the INF coefficients and then added to the INF
constant for an infested computation. The calculation (INF or NON) giving
the largest value gives the predicted chinch bug habitat status of the lawn.
The 1986 data were used to write the function, and the 1987 and 1988 data to
validate it. Although the covariance matrices were determined to be non-
homogeneous (X2=17.18, P<0.001), pooled matrices were used. The SAS
stepwise selection procedure for discriminant function variables (SAS
Institute, 1985) selected thatch thickness and percent Kentucky bluegrass as
the first two variables for inclusion in the model. They were the only two
variables determined to be significant for the model at the 0.10 level. The
initial discriminant function (1986 data) correctly discriminated non-infested
lawns 63% of the time and infested lawns 78% of the time (Table 5). In
independent tests, the function identified non-infested lawns correctly 75%
and 71% of the time and infested lawns correctly 81% and 64% (1987 and
1988 data, respectively, Table 5). Five leave-five-out jackknife tests of the
1986 data gave a range of correct classification of non-infested lawns from 62
to 75%, and of infested lawns from 70 to 83%.

The tests of the discriminant function using the 1986, 1987, and 1988 data
are graphically represented in Figures 2, 3 and 4. The curve on these figures
represents the points at which the infested and non-infested equations of the
discriminant function are equal. It was determined by setting the two

equations equal to each other, holding one of the two variables constant and

 

 

23

Table 4. Coefficients of linear discriminant function. Values of variables are
multiplied by the appropriate coefficient and then added to the constant. The
calculation giving the larger number is the predicted habitat type of the lawn in
question, either chinch bug habitat (INF) or not chinch bug habitat (NON).

 

 

Predicted Chinch Bug
Habitat Status of the Lawn

M M M
Thatch thickness .101 -.002
% Kentucky 9.601 12.865

bluegrass *

Constant -5.401 -3.382

 

* function was calculated using arc sin square root transformed data.

24

Table 5. Computer classifications of infested (INF) and non-infested (NON)
lawns using percent Kentucky bluegrass and thatch thickness variables. Data
from 1986 were used to calculate the initial discriminant frmction. Data from
1987 and 1988 are independent tests of the function. Underlined values are
percent correct classification for each group.

 

 

 

Actual
glassifigatign as (19)
Year Group MN INF
1986 MINI 8 63, 3 8
INF 2 7 2 2 7_8
1987 MN 1 6 _7_§ 2 5
INF 27 1 9 fl
1988 MN 5 2 Z_1_ 2 9

INF 14 36 g

 

 

25

 

 

in
to
E
U!
0
2
m
> .
% function
3 0.. 0 INF
dc, . 9 hCN
5‘ 20 ‘0 ,
.\° o
or : l '° 17 r r f I
0 10 20 30 40

Average Thatch Thickness (mm)

Figure 2. Plot of thatch thickness and species composition data from 1986
showing relative relationship to discriminant function line. Points
falling below the line are classified by the function as chinch bug
habitats (INF). Those above the line are classified as non-chinch
bug habitats (NON). Sixty-three per cent of the non-infested lawns
are correctly classified (i.e.fall above the line), as are 78% of the
infested lawns (i.e. fall below the line).

26

 

 

 

«a
in
2
8
2
m
>.
x
§ 40 . 0° ° " - function
g 1 000 0 INF
x 20. ° 0 o mu
32 ’ ‘°
0'4' r ' r ' l ' l
0 10 20 30 40

Average Thatch Thickness (mm)

Figure 3. Plot of thatch thickness and species composition data from 1987
showing relative relationship to discriminant function line. Points
falling below the line are classified by the function as chinch bug
habitats (INF). Those above the line are classified as non-chinch
bug habitats (NON). Seventy-five per cent of the non-infested
lawns are correctly classified (i.e.fall above the line), as are 81% of
the infested lawns (i.e. fall below the line).

 

 

27

 

 

 

m
m
in.»
2
m
>
x %
40- .
g 0 0.. ' function
r: ‘ ° . 0 INF
° 0
x 20- go 0 MN
32 00 . o o
o ‘r I ' l7 ' I ' I
O 10 20 30 40

Average Thatch Thickness (mm)

Figure 4. Plot of thatch thickness and species compostion data from 1988
showing relative relationship to discriminant function line. Points
falling below the line are classified by the function as chinch bug
habitats (INF). Those above the line are classified as non-chinch
bug habitats (NON). Seventy-one per cent of the non-infested
lawns are correctly classified (i.e.fall above the line), as are 64% of
the infested lawns (i.e. fall below the line).

28

solving for zero. The solid diamonds on the figures represent data for lawns
that were in reality infested, and the open diamonds, data for lawns that in
reality had no chinch bugs. If the value fell below the line, the lawn was
predicted as being infested (INF), if above the line, as non-infested (NON).

DISCUSSION

Thatch thickness and species composition of the turf were found to be
consistently related to chinch bug presence in lawns. Thatch, defined as a
tightly intermingled layer of living and dead roots, stems, and grass blades
that develops between the green vegetation and the soil (Beard, 1973), was
associated with both the presence and abundance of chinch bugs in lawns.
Thatch was thicker in lawns with chinch bugs than in lawns without them,
and as thatch thickness increased, the number of chinch bugs also increased
(Tables 1, 2, and 3). The correlation between thatch thickness and grass
height in 1986 probably explains the significant correlation between grass
height and chinch bug abundance in the same year. Apparently thatch .
thickness is a more reliable indicator of chinch bug abundance because thatch
thickness remained positively correlated to chinch bug abundance in 1987 and
1988 whereas grass height did not.

Thatch thickness was also positively correlated to the abundance of
predators in a lawn (Table 1). The presence of thatch makes for a more
diverse turf environment, and probably allows for a more complex trophic
organization, hence the presence of more upper-level food web members. If
reduction in predators was the primary cause of chinch bug outbreaks, a

mathematical relationship between chinch bug and predator abundances

 

29

would be expected. In this study, however, predator counts were not
significantly correlated to chinch bug counts (Table 1).

Species composition of a lawn was also an indicator of the presence or
absence of chinch bugs. Significantly higher percentages of fine fescue and
lower percentages of Kentucky bluegrass in infested lawns suggests chinch
bugs are cueing in to some factor associated with fine fescue. Turgeon
(1985) indicates that Kentucky bluegrass lawns tend to be slightly thatchier
than fine fescue lawns. This is inconsistent with my finding that there is no
correlation between thatch thickness and percent fine fescue or percent
Kentucky bluegrass (Table 1). Species composition and thatch thickness are
independent of each other in my data sets.

My data do not lend support to the hypothesis that moisture stress can
account for chinch bug outbreaks. Chlorophyll content is known to be related
to drought stress of turf. During periods of moisture stress, the plant reduces
chlorophyll production (Kramer, 1983). My data also show that as soil
moisture went down, so did the chlorophyll content (Table 1). However, no
relationship between chinch bug abundance and chlorophyll content of the
grass or soil moisture was found (Table 1). Mattson and Haack (1987) point
out that insect response to drought stress is probably non-linear. For the
insect, there is an optimum stress level of the plant, after which the insect
does less well reproductively or developmentally. Linear correlation may not
be the best way to investigate the relationship of chinch bugs to drought
stress of the turf.

The discriminant function developed with thatch thickness and species
composition data is significant for two reasons. First, such relatively high
levels of discrimination (63 to 81%, Table 5) using a function written with

only two variables indicates the close relationship of these variables to chinch

30

bug presence in a lawn. Although this relationship can only be said to be
correlative and not cause and effect, it does indicate a direction for future
research on variables important to chinch bug development. Cultural
practices that reduce thatch may also be helpful for chinch bug management.

Further investigation of why lawns with chinch bugs differ in species
composition from lawns without chinch bugs could be useful. A certain
proportion of fine fescue and Kentucky bluegrass may favor chinch bug
development or survival. Another hypothesis to consider in future work is
that chinch bug feeding activity may be selecting against Kentucky bluegrass
and for fine fescue.

Second, this discriminant function may have practical application.
Discriminant functions have been previously used as aids in management
decisions (Anderson and Shugart, 1974; Conner and Adkisson, 1976;
Hand,198l). It may be useful for lawn-care professionals to establish a
chinch bug risk factor for a lawn based on parameters that are relatively easy
to measure. High risk lawns (those determined to be potential chinch bug
habitats) could be more intensely monitored for chinch bugs, thus more

efficiently allocating monitoring time.

31

LITERATURE CITED

Anderson, S. H. and H. H. Shugart, Jr. 1974. Habitat selection of breeding
birds in an east Tennessee deciduous forest. Ecology 55:828-837.

Anonymous. 1986. Farm Chemicals Handbook. G. L. Berg, ed. Meister
Publishing Co. Willoughby OH.

Baker, P. B., R. H. Ratcliffe and A. L. Steinhauer. 1981. Tolerance to
hairy chinch bug feeding in Kentucky bluegrass. Environ. Entomol.
10:153-157.

Beard, J. 1973. Turfgrass: science and culture. Prentice-Hall, Inc.
Englewood Cliffs, NJ.

-Cockfield, S. D., and D. A. Potter. 1985. Predatory arthropods in high and
low maintenance turfgrass. Can. Entomol. 117:423 -429.

Conner, R. N. and C. S. Adkisson. 1976. Discriminant function analysis: a
possible aid in determining the impact of forest management on
woodpecker nesting habitat. Forest Sci. 22:122-127.

Duble, R. L. and H. D. Niemczyk. 1979. Insects: once a nuisance, today a
problem. Weeds, Trees, and Turf May/Junez20-23.

Hand, D. J. 1981. Discrimination and classification. John Wiley and Sons,
New York.

Johnson, G. V. 1974. Simple procedure for quantitative analysis of
turfgrass color. Agron. J. 66:451-459.

Knipling, E. F. 1979. The basic principles of insect population suppression
and management. U. S. D. A. Agriculture Handbook No. 512, 623

PP-

Kramer, R]. 1983. Water relations of plants. Academic Press, Orlando,
FL.

Mattson, W. J. and R. A. Haack. 1987. The role of drought in outbreaks of
plant-eating insects. Bioscience 37:110-118.

 

32

N iechyk, H. D. 1984. Turf insect control guide. Weeds, trees and turf.
May/June 1984: 28-46

Ratcliffe, R. H. 1982. Evaluation of cool-season turfgrasses for resistance
to the hairy chinch bug in Advances in turfgrass entomology. H. D.
Niemczyk and B. G. Joyner, eds. Hammer Graphics, Piqua, OH.

Reinert, J .A. and SH. Kerr. 1973. Bionomics and control of lawn chinch
bugs. Bull. Entomol. Soc. Am. 19:91-92.

Reinert, J.A. and KM. Portier. 1983. Distribution and characterization of
organophosphate-resistant southern chinch bugs (Heteroptera:

Lygaeidae) in Florida. J. Econ. Ent. 76:1187-1190.

SAS Institute, Inc. 1985. SAS user's guide: Statistics, version 5 edition.
SAS Institute, Inc. Cary, NC.

Sokal, R. R. and F. J. Rohlf. 1981. Biometry. W. H. Freeman and Co.,
NY. 859 pp.

Tashiro, H. 1987. Turfgrass insects of the United States and Canada.
Cornell University Press, Ithaca NY.

Turgeon, A. J. 1985. Turfgrass management. Reston Publishing Co.,
Reston VA. 416 pp.

Turgeon, A. J. and F. A. Giles. 1984. Turfgrasses of Illinois. Illinois
Coop. Ext. Serv. Circ. 1105, 16 pp.

CHAPTER 2
Influence of Thatch Layer on Populations of

Chinch Bugs (Blissus leucopterus HemipterazLygaeidae)

in Turfgrass

33

INTRODUCTION

Thatch is defined as a layer of living and dead roots, stems, and grass
blades that develops between the green vegetation and soil surface in
turfgrass. Excessive accumulation of thatch, such as 1.2 cm or more on a
Kentucky bluegrass turf, is considered to be undesirable. In addition to
increasing disease problems and decreasing drought stress and effectiveness
of pesticides, thick thatch can contribute to insect problems (Beard, 1973).
The hairy chinch bug (Iiis_su_s leucopterus Montandon HemipterazLygaeidae)
is a major pest of turfgrass in eastern North America (T ashiro, 1987),
especially on home lawns. It has been suggested that chinch bugs are more
likely to be found in turfgrass with thick thatch (N iemczyk, 1981). However
there are no experimental data to support this. What benefit heavy thatch may
give chinch bugs is not clear. Kennedy (1981) suggests that heavy thatch
may provide protection for nymphs and overwintering adults. The insects are
known to seek thatch or debris in which to overwinter, suggesting that this
type of environment is beneficial to survival through the cold months. The
thick spongy thatch produced by St. Augustine grass provides a refuge for
the southern chinch bug (13m insularis (Say), Reinert and Kerr, 1973),
perhaps imparting protection from predators or from desiccation.

We investigated the relationship of thatch to chinch bug abundance by: (1)
artificially inducing thatch in the field to determine the effect on chinch bug
populations; (2) collecting and releasing chinch bugs into thatched and
dethatched areas to observed short term habitat preferences; (3) investigating
the effect of thatch on predation of the chinch bug by the big-eyed bug in the ,

laboratory; and (4) surveying lawns in the Lansing, MI, area.

34

 

 

 

35

MATERIALS AND METHODS

Induced Thatch Experiment

A population of chinch bugs in the lawn of the Botany and Plant
Pathology Field Research Center (Michigan State University, East Lansing,
MI) was studied during 1986 and 1987. In 1986, eight 36.6 m2 plots were
established in a chinch bug infested area of the lawn. All plots received full
sun. Four of the plots were designated as controls and the other four were
treated biweekly with the fungicide mancozeb ("Dithane M-45", Rohm and
Haas) at 2.35 oz AI/lOOO ft2 in 4 gal. water per 1000 ftz, approximately 60%
of the lowest recommended rate for this product. Mancozeb is known to
increase thatch accumulation (Smiley et. al, 1985). Chinch bugs were
sampled by visually searching a 930 cm2 area for 3 min. Numbers of instars
one and two were lumped together, as were numbers of instars three and
four, due to difficulty in differentiating between these instars in the field.
Four counts were made per plot. Plots were sampled approximately biweekly
for a total of eight counts. Notes were made as to the presence of dead
insects sporulating with fungi. Dead chinch bugs that were sporulating with
a white powdery fungus were noted. The first count was taken on May 28
and the last on October 10. Peak population sizes of instars Were interpolated
as the value at the 50% point of the cumulative total chinch bugs obServed in
each instar group.

In 1987, fourteen 36.6 m2 plots were established in a different area of the
same lawn used in the 1986 experiments. seven were treated biweekly with
mancozeb, the other seven were designated as controls. Because the

distribution of chinch bugs is known to be clumped (Liu and McEwen,

36

1979), a transect method was used to sample in 1987. Transects were
defined by a loop of string stretched between two 2.5 cm wide wooden row
markers placed 1.5 m apart. Chinch bugs were sampled weekly using six
randomly placed transects per plot. Irrstars one and two or three and four
were grouped together in counts. A total of 19 counts were made; the first on
May 4 and the last on September 17. Degree days were calculated using the
Baskerville-Emin (1969) method with a base of 15°C (rounded up from
14.6°C, Mailloux and Streu 1981).

One hundred and sixty insects (twenty from each plot) were collected on
Sept. 22, 1986, and brought back to the lab. They were individually placed
in tissue culture wells filled with a thin layer of plaster of Paris. Each mini-
sporulation chamber was kept moist by introducing water through a small
needle hole in the lid over each well. Mortality and incidence of fungus
sporulation for the bugs was recorded. Fungi were identified as Beauveria

bassiana by microscopic examination (Barnett and Hunter,1972).

Dethatching Experiment

Eight 3.7 m2 plots , were dethatched using a "Mataway" dethatching
machine in a mature stand of "Jamestown" fine fescue at the Hancock
Turfgrass Research Center (Michigan State University, East Lansing, MI)
during August of 1988. Thatch thickness ranged from 10 to 50 mm. Two
3.7 m2 non-dethatched plots and two 3.7 m2 dethatched plots were arranged
inside a 14.8 m2 block such that the dethatched plots were diagonal to each
other and adjacent to non-dethatched plots on two sides. Each block was
surrounded by aluminum lawn edging sunk to a height of 12.7 cm to
discourage chinch bug migration out of blocks. Four such blocks were used.

On August 10, 100 adult chinch bugs were released into the center of each of

37

the four plots in each block , for a total of 1600 bugs used. These bugs had
been recently collected from an East Lansing lawn that was 94% Kentucky
bluegrass and 6% fine fescue. Three-minute visual counts of a 930 cm2 area

in the center of each plot were made at 1, 3, and 5 days post-release.

Predation Experiment

Thatched and non-thatched chambers were set up in the lab during. July
and August of 1988. Slabs of turf were taken from a mature stand of
"Jamestown" fine fescue at the Hancock Turfgrass Research Center. Thatch
thickness in this turf ranged from 10 to 50 mm. A small section of the turf
slab containing approximately twelve 30 mm tall grass plants was placed on
top of moist silica sand in a 2 oz. clear plastic dict cup. Thatch material
removed from the same slab was added to the chamber, surrounding the plug
of turf to a depth of 10 mm. A hole covered with mosquito-netting in the lid
of the chamber provided ventilation. Non-thatched cups were prepared using
slabs of turf from a dethatched section of the same area. No thatch was added
to these cups, leaving the area around the plug of turf as exposed silica sand.
On August 5, twenty adult chinch bugs collected from five different lawns
were added to each of 10 thatched and 10 non-thatched cups. After a 10
minute acclimation period, 0, 2, 4, 8, or 16 adult big-eyed bugs (Geocoris
bullatus (Say); identified to species at The Center for Insect Identification,
Lansing, Michigan) collected from three lawns were added to the chambers.
There were two replicates of each treatment type, for a total of 20 chambers.
Chambers were maintained for seven days in an air-conditioned room with
temperatures between 25 and 27 ° C and relative humidity between 72 and
80%. The chambers were then dismantled and live and dead bugs counted.

The experiment was repeated August 26 to September 1. Then, numbers of

 

38

big-eyed bugs that were added were changed to 0, 10, 20, and 30 per
chamber, for a total of eight thatched and eight non-thatched chambers.

Survey

One hundred and eight lawns were surveyed in the Lansing Michigan area
in 1986 and 1987 as part of a larger study on relationships of lawn parameters
to chinch bug abundance (see Chapter 1). A subset of 25 infested and nine
non-infested lawns were sampled for the two consecutive years. Numbers
of insects in five transects per lawn were counted to estimate chinch bug
abundance. Transects were sampled as described under the induced thatch
experiment. Thatch was measured to the nearest mm at five randomly

selected points in each lawn and an average thatch thickness was calculated.
RESULTS

Induced Thatch Experiment.

In both years. the fungicide treated plots supported larger average
populations of chinch bugs than did the control plots (Figures 5 and 6).
Chinch bug population densities in fungicide treated plots were compared to
that in control plots by fitting linear regression models (SAS Institute, 1985)
to fungicide and control data and determining if the slopes were different. In
1986, the linear model of chinch bug population density in control plots had a
slope of 0.067 whereas the slope for chinch bug population model in
fungicide treated plots was .137. The two slopes were significantly different
(t=2.514, df=10, 0.02<P<0.05). In 1987, the slope of the chinch bug
population development model for control plots was 0.093 and the slope for
fungicide treated plots was 0.187 (t=7.40, df=26, P<0.001).

 

39

    
    

80 -
tn
8’
ca 50 ' Mancozeb
.1:
o
.E
5 4o -
o
.2
E
E 20 ' Control
a
U

0

 

 

. _, . , . I . I . l . l
0 100 200 300 400 500 600
Degree Days (base 15°C)

Figure 5. Cumulative number of chinch bugs in control and mancozeb
treated plots in 1986. Data are sums of average number of bugs
observed in 3720 cm2 in each of 4 plots. Slopes of lines are
significantly different (control: m=.0665, mancozeb: m=.137,
t=2.51, df=10, .02<P<.05).

40

 

 

 

150" Mancozeb
,, 125-
g . Control
m
g 100-
0
E d
5 75-
o d
.2
5 so-
: G
E
8 25- N ,
‘ ‘ N1+2
o r I ' I r I r I
0 200 400 600 800
Degree Day (base 15°C)

Figure 6. Cumulative number of chinch bugs in control and dithane treated
plots in 1987. Data are sums of average number of bugs observed
in 6-transects in each of 7 plots. Slopes of lines are significantly
different (Control: m=.094, mancozeb: m=.186, t=7 .40, df=26,
P<0.001). Vertical bars represent peak density of instar groups,
determined as the 50% point in the cumulative instar group count.
N1+2 means the group of nymphal instars 1 and 2, etc, and A

stands for adult.

 

41

Chinch bug development rate was determined in 1987 by plotting the 50%
point of the cumulative count of each of the instar groups for the control and
fungicide treated groups. The chinch bugs in the fungicide treated and control
plots had similar rates of development in 1987 as evidenced by the similar
timing of instar population peaks (Figure 6). The group composed of instars
one and two peaked at 186 degree days in the control plots, whereas it peaked
at 212 degree days in the fungicide treated plots. The third and fourth instar
combined group peaked at 346 degree days days in the control, and 366
degree days in the fungicide treatment. Fifth instars and adults reached
maximum population levels at 451 degree days and 724 degree days,
respectively, in control plots and 450 degree days and 724 degree days,
respectively, in the fungicide treatments.

Symptoms of phytotoxicity were noticed in the treated turf during the
middle of July in 1987. This may have been caused by drought conditions.
Treated turf was noticeably more yellow than the non-treated turf. Thatch
was significantly thicker in treated plots than in the control plots in 1987
(10.32 mm and 3.54 mm, respectively, t=6.2, P<0.001). Thatch was not
measured in 1986.

Sporulation of chinch bugs collected in September of 1986 with the insect
pathogenic fungus Beauveria bassiana did not differ between fungicide treated

 

plots and controls. Of insects from fungicide treated plots an average of
8.6% sporulated with Beauveria, compared to 9.2% in control plots. These
infection rates are not significantly different (t= 0.07, P>0.50). No other
fungal pathogens were found to sporulate from chinch bugs collected from
the field plots. Over the course of the field season, ten out of 228 bugs

(4.4%) observed in the control plots sporulated with an undetermined

 

42

powdery white fungus, compared to 12 out of 356 (3.4%) in the fungicide
treated plots.

Dethatching Experiment

There were significantly more chinch bugs found in plots with thatch
compared to dethatched plots 24 hrs after release (T able 6, t=2.47,
0.02<P<0.05). The trend remained the same at 72 and 120 hrs after release,
although the counts were no longer statistically significantly different (for 72
hrs; t=l.77, 0.10<P<0.2 and for 120 hrs; t=l.76, 0.10<P<0.20).

Predation Experiment

Chinch bug mortality was not correlated with changing densities of big-
eycd bugs (Figures 7 and 8). There was 50% mortality of big-eyed bugs
during the first experiment, and 90% during the second. Therefore, data are
graphed using mean number of live big-eyed bugs during each experiment,
determined by adding the number of live bugs at the beginning to the number
of live bugs at the end and dividing by two. Mortality of chinch bugs did not
increase with increasing big-eyed bug densities in the first experiment (Figure
7). It appeared as though chinch bugs may have had increased survivorship
in the thatch treatment as compared to the no thatch treatment; however,
neither the slopes nor the intercepts of the lines were significantly different.
There was little chinch bug mortality during the second experiment (Figure
8). Big-eyed bugs were observed to feed on chinch bugs in the laboratory,
sometimes with more than one big-eyed bug feeding on a single chinch bug.

Big-eyed bugs also fed on each other.

43

Table 6. Mean number of chinch bugs observed in thatched and dethatched
turfgrass plots. Variance is reported in parentheses.

 

 

 

 

Days after release With thatch Without thatch
1 6.88 2.12
(28.64) (0.98)
3 4.88 3 .00
(6.70) (2.29)
5 1.71 . 0.86

(1.71) (0.86)

 

44

20'

16 " thatch

 

124

  
 

Survlvlng Chlnch Bugs

8 no thatch
4
o I ' I ' l ' I ' I r I ' I ' I ‘

 

O 2 4 6 8 1 0 1 2 1 4
Ave. # Big-Eyed Bugs

Figure 7. Number of chinch bugs surviving one week confinement with
different numbers of big-eyed bugs (BEB), first experiment. Due
to mortality of BBB during the experiment, BEB numbers are
reported as the average live BEB. Slopes and intercepts of lines are
not significantly different (slope of non-thatch treatment =1.41,
thatch treatment=1.56, t=l.l95, P>.05; for test of intercepts,
t=0.322, P>.05) '

45

2° (thatch
O
“’ 16- R I
g, nothatch
m
512-
.E
g d
L)
a 3"
.E
.2 d
s 4-
‘0 .
orI'I'I'I'I‘I'I

 

 

0 2 4 6 8 10 12 14
Ave.# BIg-Eyed Bugs

Figure 8. Number of chinch bugs surviving one week confinement with
different numbers of big-eyed bugs (BBB), second experiment.
Due to mortality of BBB during the experiment, BEB numbers are
reported as the average live BEB. Slopes and intercepts are not
significantly different.

 

46

Survey

Thatch thickness and chinch bug density were significantly positively
correlated (r=0.325, n=108, P<0.0006). On lawns for which there were two
years of data, I used a paired t-test to compare thatch accumulation for the two
years in both infested and non-infested lawns. Thatch significantly increased
from 1986 to 1987 in infested lawns (from a mean of 6.5 mm to a mean of 10
mm, d=—3.55, n=25, t=-2.73, 0.01<P<0.02) but did not significantly change
in lawns without chinch bugs (4.0 mm to 5.3 mm, d=-l.29, n=9, t=-0.667,
P>0.5).

DISCUSSION

Accumulation of thatch is caused by an imbalance in the rate of production
and decay of organic matter (Beard, 1973). Many cultural factors are known
to contribute to the accumulation of thatch. Some of these are the growth
characteristics of the turfgrass cultivar (Sheannan et. al, 1980), high nitrogen
levels (Potter et al., 1985), acidic conditions of the soil, infrequent or
excessively high cutting levels (Beard, 1973; Shearrnan et al., 1980), failure
to remove clippings (Soper, et al., 1988), and treatment with certain
herbicides (Turgeon, et al., 1975), insecticides (Streu, 1973) and fungicides
(Smiley et al., 1985). Thatched turf is also generally shallow-rooted, making
it more susceptible to temperature stress (Dunn et al., 1981). V

Chinch bugs were found in larger numbers in lawns that had thick thatch.
However, the significant correlation implies only a mathematical relationship,
not causality. Chinch bugs may be responding to, or, alternatively,
influencing thatch thickness of a lawn. Damage caused to vascular tissues by

chinch bug feeding activity may prevent water and nutrients from reaching

 

47

leaves and shoots, thus killing the plant (Painter, 1928) . Baker et a1. (1981)
found a higher percent dry matter content in turf of chinch bug infested
lawns. A significant increase in thatch thickness from 1986 to 1987 was
found in chinch bug infested lawns in this study. No such increase was
observed in non-infested lawns. One hypothesis worthy of future
investigation is that chinch bug feeding injury contributes to accumulation of
thatch.

Alternatively, chinch bug populations may be responding to the increase in
thatch, not causing it. The fungicide mancozeb is known to increase thatch
accumulation by decreasing the degradation of organic material (Smiley et al.,
1985). The thick thatch induced by fungicide treatment did not affect the rate
of development of chinch bugs in those plots as evidenced by the similar
timing of instar population peaks for fungicide and control plots (Figure 6).
These peaks differed by a maximum of 87 degree days (base 15°C) from
those determined by Mailloux and Streu (1981). Experimentally increasing
thatch thickness with low rate mancozeb treatments did, however, increase
chinch bug abundance as compared to controls (Figures 5 and 6). Beauveria
Ma activity was monitored in these plots because Beauveria has been
observed to infect large numbers of chinch bugs. in turfgrass (Bartlett and
Lefebvre, 1934; Kennedy, 1981). Although mancozeb is known to be active
against Beauveria Mam (Loria et al., 1983), no differences among
treatments were found in the number of dead chinch bugs sporulating with
fungus in field plots or in moist chambers in the laboratory. No other fungal
pathogens were found to sporulate from chinch bugs collected from field
plots. It is possible that mancozeb treatment suppressed predator or
parasitoid activity. However, no differences were detected in the number of

predators observed in mancozeb compared to control plots, and no

48

parasitoids emerged from field collected bugs. The difference in chinch bug
abundance between mancozeb and control treatrnents may be owing to either
a higher oviposition rate or a lower mortality rate in the mancozeb plots.
Direct effects of mancozeb on predators or indirect effects such as prdtection
from predators and/or protection from extremes in temperature and humidity
afforded by the thicker thatch may have contributed to reduced chinch bug
mortality in these plots.

Chinch bugs are also attracted to thatchy areas. There were significantly
more bugs in the thatched compared to the dethatched plots 24 hrs after
release of the bugs (Fable 6). Because chinch bugs were not confined to our
study plots it is possible that the bugs were mostly moving out of all plots
into surrounding turf, and the observed differences were due ascribable to
longer residence times by Chinch bugs in thatched plots.

Possible benefits for chinch bugs living in a thickly thatched environment
are not clear. Probabilities of survival may increase in thick thatch by reduced
predator efficiency. The big-eyed bug (Geocoris Brilams) is known to be a
predator of the chinch bug, and is often found in large numbers in chinch bug
infested lawns (Mailloux and Streu, 1981). The large eyes possessed by the
big-eyed bug suggest that it relies heavily on vision to find its prey. In a
thatchy environment, it may be more difficult for big-eyed bugs to locate
chinch bugs because chinch bugs tend to hide in the thatch. The impact that
the big-eyedbug has on chinch bug populations has not been determined.
Mailloux and Streu (1981) did not find a correlation between chinch bugs and
big-eyed bug populations. In our laboratory studies, we observed the big-
eyed bug to feed upon the chinch bug, but we did not see a significant effect
on adult chinch bug mortality (Figures 7 and 8). Immature chinch bugs were
not offered as prey but actually may be the preferred food source. The high

49

source. The high mortality rate of the big-eyed bug during the second run of
the experiment (90% over a one-week period) may have eliminated any
potential predation effect on the chinch bugs. More experiments are required
to determine whether big-eyed bugs have a significant impact on chinch bug
populations in turfgrass.

The results of this study indicate that chinch bug abundance is closely
linked to the thatch thickness of home lawns. I have presented and tested
several hypotheses for why thatch thickness is related to chinch bug
abundance. It may be hypothesized that grass species composition is the
driving force affecting chinch bug abundance and that thatch thickness is
merely correlated to species composition. However, in Chapter 1 I showed
that thatch thickness was not related to species composition of home lawns.
Three hypotheses that deserve attention are: 1) thatch helps chinch bugs
escape predation; 2) thatch reduces mortality from environmental stress; and

3) chinch bug feeding injury induces thatch.

 

50

LITERATURE CITED

Baker, P.B., R. H. Ratcliffe, and AL. Steinhauer. 1981. Tolerance to hairy
chinch bug feeding in Kentucky bluegrass. Environ. Entomol. 10:153-
157.

Barnett, H. L. and B. B. Hunter. Illustrated genera of imperfect fungi.
Burgess Publishing Co., Minneapolis, 241 pp.

Bartlett, K. A. and C. L. Lefebvre. 1934. Field experiments with Beauveria
bassiana (Bals.) Vuill., a fungus attacking the European corn borer. J.
Econ But. 27: 1 147-1 157.

 

Baskerville, G. L. and P. Emin. 1969. Rapid estimation of heat
accumulation from maximum and minimum temperatures. Ecology
50:5 14-517.

Beard, J. B. 1973. Turfgrass science and culture. Prentice-Hall, Inc.
Englewood Cliffs, N .J . 658 pp.

Dunn, J .H. K. M. Sheffer, and P. M. Halisky. 1981. Thatch and quality of
Meyer zoysia in relation to management. Agron. J. 73:320-323.

Kennedy, M. K. 1981. Chinch bugs: biology and control. American Lawn
Applicator, August, pp. 12-15.

Liu, H. J. and F. L. McEwen. 1979. Use of temperature accumulations and
sequential sampling in predicting damaging populations of Blissus
leucopterus hirtus. Environ. Entomol. 8:512—515.

 

Loria, R., S. Galaini and D. W. Roberts. 1983. Survival of the innoculum
of the entomopathogenic fungus Beauveria mm as influenced by
fungicides. Environ .Entomol. 12:1724-1726.

Mailloux, G. and H. T. Streu. 1981. Population biology of the hairy chinch

bug (Blissus leugopterus, Montandon:HemipterazLygaeidae). Ann.
Soc. Ent. Quebec 26:51-90.

 

51

Niemczyk, H. D. 1981. Destructive turf insects. Gray Printing Co.,
Fostoria, OH 48 pp.

Painter, R. H. 1928. Notes on the injury to plant cells by chinch bug
feeding. Ann. Entomol. Soc. Am. 21:232-241.

Potter, D. A., B. L. Bridges, and F. C. Gordon. 1985. Effect of N
fertilization on earthworm and microarthropod populations in Kentucky
bluegrass turf. Agron. J. 77:367-372.

Reinert, J. A. and S. H. Kerr. 1973. Bionomics and control of lawn chinch
bugs. Bull. Ent. Soc. Am 19:91-92.

SAS Institute, Inc. 1985. SAS user's guide: Statistics, version 5 edition.
SAS Institute, Inc. Cary, NC.

Shearrnan, R. C., E. J. Kinbacher, T. P. Riordan, and D. H. Steinegger.
1980. Thatch accumulation in Kentucky bluegrass as influenced by
cultivar, mowing, and nitrogen. HortScience 15:312-313.

Smiley, R. W., M. Craven Fowler, R. T. Kane, A. m. Petrovic and R. A.
White. 1985. Fungicide effects on thatch depth, thatch decomposition
rate, and growth of Kentucky bluegrass. Agron. J. 77:597-602.

Soper, D. Z., J. H. Dunn, D. D. Minner, and D. A. Sleper. 1988. Effects
of clipping disposal, nitrogen, and growth retardants on thatch and tiller
density in zoysiagrass. Crop Sci 28:325-328.

Streu, H. T. 1973. The turfgrass ecosystem: impact of pesticides. Bull.
Entomol. Soc. Am. 19:89-91.

Tashiro, H. 1987. Turfgrass insects of the United States and Canada.
Cornell University Press. 391 pp.

Turgeon, A. J., R. P. Freeborg, and W. N. Bruce. 1975. Thatch
development and other effects of preemergence herbicides in Kentucky
bluegrass turf. Agron. J. 67:563-565.

Chapter 3

Feeding Preference of Chinch Bug (Blissus leucopterus
HemipterazLygaeidae) for Fine Fescue and Kentucky Bluegrass

52

INTRODUCTION

Feeding preferences of insects may be the primary separation force causing
the evolutionary diversity in phytophagous species (Bush 1975; Dethier,
1958). The chinch bug, Blissus leucopterus, has two subspecies, B. l.

 

leucopterus and B. 1. hirtus (Leonard, 1966). The two races are separated in
geographic range but even more so by host preference. B. l leucopterus feeds

mostly on wheat, sorghum, and corn, while B. l. hirtus feeds primarily on

 

turfgrasses, such as Kentucky bluegrass, fine fescue, and the ryegrasses
(Leonard, 1966). Chinch bug preferences for certain host plants have not
been shown for B. I. leucopterus (Stuart et al., 1985; Wilde et al., 1986).
Ratcliffe (1982) found that B. l. him—s, the hairy chinch bug, has a preference
for certain cultivars of Kentucky bluegrass. However, feeding preference
among cormnon home lawn grass species has not been addressed. In this
investigation I sought to determine the feeding preference of the hairy chinch
bug for two of the most common temperate region home lawn turfgrasses,

Kentucky bluegrass (Bo_a pratensis) and fine fescue (Festuca rubra).

 

MATERIALS AND METHODS

Standard golf course cup-cutter plugs of "Fylking", "Adelphi", and
"Kenblue" Kentucky bluegrass cultivars and "Biljart" and "Jamestown" fine
fescue cultivars were taken from the Hancock Turfgrass Research Center on
the Michigan State University (East Lansing, MI) campus. These were
planted in clay pots in the greenhouse where they received uniform watering

and clipping treatment. Because only two cultivars of fine fescue were

53

54

available at the Hancock Center, a third , "Wintergreen", was planted in the
greenhouse one month before the beginning of the test.

Resting Habitat Preference

Resting habitat preferences for B. 1. flags were tested on July 15 and
16, 1987. Standard cup-cutter plugs of each of the six cultivars were cut into
quarters. One quarter of each of the six cultivars was placed on the soil in an
20 cm diameter clay pot, alternating Kentucky bluegrass quarters with fine
fescue quarters. Six permutations of cultivar quarters arranged in this fashion
were possible. Two replicates of each permutation were produced, for a total
of 12 test arenas. The grass in each arena was surrounded by a clear plastic
collar, 53 cm in circumference, and 17 cm tall, placed 2 cm into the soil. The
area around the turfgrass and collar was covered by white silica sand.
Twenty chinch bugs (5 adults, 12 fifth instars and 3 third or fourth instars)
were introduced into the center of the arena, and the top of the collar was
covered with a piece of parachute cloth secured with elastic banding. One-
fifth of the chinch bugs used had been reared from eggs according to the
method described by Baker et al. (1981). Because of a low success rate in
chinch bug rearing, the rest of the bugs used in the experiment were collected
as immatures and maintained on corn stalk sections through at least one
moult. After 24 hrs., the arenas were dismantled and the cultivar quarters

removed and visually searched for chinch bugs.

Feeding Preference Tests
Feeding preference test chambers were prepared using 90 mm plastic
Petri dishes. Five 6mm diameter holes were drilled along the top edge of the

Petri dish. The four outer holes were covered with mosquito netting and

 

55

served to ventilate the chamber. The center hole was fitted with a cork and
provided an opening for introduction of the chinch bugs into the chamber.
Twenty cc of white silica sand was placed into the bottom of the dish and was
wetted with 6 ml of water. One plant of Kentucky bluegrass and one plant of
fine fescue were placed in the sand. The lid of the dish was attached by a
double layer of Parafilrn and the whole chamber gently tapped on one edge to
cause the sand to collect in the bottom ofthe chamber (Figure 9). Completed
chambers were stabilized for 24 hrs before introduction of the chinch bugs.
Five replicates of each of the nine permutations of cultivar combinations (three
cultivars each of the two grass species) were set up, for a total of 45
chambers.

Immature chinch bugs were collected from three heavily infested lawns
of varying grass composition in the Lansing, MI area June 30 and July 27,
1988. Bugs were maintained in the lab on corn stalk sections for at least a
week before being used in any experiment. On August 5, 1988, a single fifth
instar chinch bug was introduced into each chamber. The chambers were kept
up-right in a rack and the bugs were observed every fifteen minutes beginning
at 8 AM and continuing until 3 PM for a total of 29 observations on each bug.
Feeding was recorded as positive when the bug was observed to have its
proboscis inserted into the plant. Observations took place under a
combination of fluorescent and incandescent light in a lab at 25°C and 80%
relative humidity. The experiment was repeated on August 11, 1988 using a
new set of test bugs. The difference between the number of feeding
observations on Kentucky bluegrass and fine fescue for each chinch bug was

determined and used to calculate a tvalue for comparison in a paired t-test.

56

 

Figure 9. Choice chamber used in feeding preference test. The chamber
consisted of a modified 90 mm plastic Petri dish. One fine fescue
and one Kentucky bluegrass plant were held upright in moist white
silica sand.

57

RESULTS

Two hundred and one of the 240 chinch bugs introduced into the resting
habitat preference arenas were recovered. Of these, 113 were found in
Kentucky bluegrass plug quarters and 88 were found in fine fescue plug
quarters. Given an expected ratio of 50% of the bugs in each of the two turf
types, a log likelihood ratio test value of 3.12 (0.05<P<0.10) was found.
Although the value was not significant at the .05 level, there was some
indication that the chinch bugs were preferentially resting in the Kentucky
bluegrass sections.

Of the 90 chinch bugs observed in the feeding preference experiments,
54 fed only on Kentucky bluegrass, 7 fed only on fine fescue, 22 fed on
both, and 7 did not feed. Subtracting the number of observations of feeding
on fine fescue from the number of observations of feeding on Kentucky
bluegrass for each bug yielded differences (D 's) for the two replicates of the
experiment of 5.98 and 9.05, with variances of 101.87 and 105.2,
respectively. These translate into paired t-test values of 3.79 and 3.54
(df=41), which are both significant at P<0.001. Chinch bugs fed

significantly more on Kentucky bluegrass than on fine fescue plants.

DISCUSSION

This study indicates that Blissus leucopterus hirtus prefer to feed on

 

 

Kentucky bluegrass over fine fescue. Several limitations of this experiment
that could affect the results should be pointed out. First, stress to grass
plants during set-up of the choice chambers may have affected plant

palatability (Risch, 1985). The chinch bugs may feed as early instars on the

58

fine blades of fine fescue. Second, field collected chinch bugs could have
had food plant preferences imprinted during the early instars that affected
their choice in these experiments even after being held on com plants for at
least seven days prior to the experiment. In a previous study Davis and
Smitley (in prep.) found that chinch bugs are most typically found in lawns
with a moderate percentage of fine fescue and a significantly lower percentage
of Kentucky bluegrass as compared to lawns without chinch bugs. Yet, our
feeding preference study suggests they prefer to feed on Kentucky bluegrass.
At least three hypotheses could explain this apparent discrepancy between
feeding preference and observed habitat. Chinch bugs could be causing
higher mortality to the Kentucky bluegrass in mixed Kentucky bluegrass/fine
fescue lawns, reducing the proportion of Kentucky bluegrass present. The
presence of fine fescue may favor chinch bug survival, even though it is not a
preferred food plant. Given that some chinch bug infested lawns were
composed entirely of fine fescue, this plant had served as a food plant.

Third, something in the laboratory experiment was different enough from
natural conditions such that the bugs behaved atypically. Although host
preferences are not always correlated with host suitability, discrimination
between host plants is expected to evolve toward a maximization of encounter
rate, oviposition probability, and host suitability (Rausher, 1983). Studies
on the development and oviposition of the chinch bug on these host plants
under laboratory and field conditions are necessary to more completely

understand the importance of these two grasses in hairy chinch bug ecology.

59

LITERATURE CITED

Baker, P. B., R. H. Ratcliffe, and A. L. Steinhauer. 1981. Laboratory
rearing of the hairy chinch bug. Environ. Entomol. 10:226-229.

Bush, G. L. 1975. Modes of animal speciation. Annu Rev. Ecol. Syst.
6:334-364.

Dethier, V. G. 1958. Evolution of feeding preferences in phytophagous
insects. Evolution 8:33-54.

Leonard, D. E. 1966. Biosystematics of the "Wm: complex" of the
genus Blissus. Connecticut. Agric. Exp. Sta. Bull. 677, pp. 1-45.

 

Ratcliffe, R. H. 1982. Evaluation of cool-season turfgrasses for resistance
to the hairy chinch bug. In Advances in turfgrass entomology, B. G.
Joyner, ed. Hammer Graphics, Piqua OH.

Rausher, M. D. 1983. Ecology of host-selection behavior in phytophagous
insects. h Variable plants and herbivores in natural and managed
systems, R. F. Demo and M. S. McClure, eds. Academic Press.

Risch, S. J. 1985. Effects of induced chemical changes on interpretation of
feeding preference tests. Ent. Exp. App. 39:81-84.

Stuart, J ., G. Wilde, and J. H. Hatchett. 1985. Chinch bug
(HeteropterazLygaeidae) reproduction, development, and feeding

preference on various wheat cultivars and genetics sources. Environ.
Entomol. 14:539-543.

Wilde, G., J. Stuart, and J. H. Hatchett. 1986. Chinch bug
(HeteropterazLygaeidae) reproduction on selected small grains and
genetic sources. J. Kansas Ent. Soc. 59:550-551.

 

SUMMARY

This research has shown that chinch bug presence and abundance in a
lawn is related to the thickness of the thatch and species composition of the
turf. Surveys of parameters of the chinch bug Mus leucopterus) turfgrass
environment examined over a three year period in a 108 home lawns in the
greater Lansing Michigan area showed thatch thickness to be the only variable
correlated to chinch bug abundance in all three years. It is not clear whether
chinch bugs are responding to thatch thickness, contributing to thatch
thickness, or whether thatch thickness and chinch bug abundance are both
affected by a third variable that was not accounted for in this study. The fact
that thatch became thicker over a two year period in chinch bug infested
lawns but did not change in non-infested ones may mean that chinch bugs are
contributing to thatch thickness. Increases in chinch bug populations in
research plots in which thatch development was induced by repeated
fungicide applications leads me to believe that thick thatch imparts some
benefit to survival or reproduction of chinch bugs. Chinch bugs that were
released into areas with thatch and areas that were dethatched appeared to
have at least a short-term habitat preference for turf with thatch. Predation
pressure on chinch bug populations may be lower in turf with thick thatch.
Big-eyed bugs (Geocoris MM) fed on adult chinch bugs in the laboratory,
but confinement with big-eyed bugs did not significantly affect chinch bug

population sizes in the laboratory.

60

 

61

There was significantly more fine fescue (fistula _I‘Bbfl) and less
Kentucky bluegrass (m pratensis) in chinch bug infested lawns as compared
2 to non-infested lawns. When tested in the laboratory, chinch bugs were
found to feed more on Kentucky bluegrass than on fine fescue. There was a
tendency for chinch bugs to hide in Kentucky bluegrass preferentially over
fine fescue, although the difference was not significant. This is contrary to
findings that showed chinch bugs were most often found in lawns with a
higher fine fescue and lower Kentucky bluegrass content compared to lawns
that did not have chinch bugs. This discrepancy may be explained by
feeding preferences of chinch bugs for Kentucky bluegrass causing
differential mortality of the Kentucky bluegrass in infested lawns, thus
reducing the relative proportion of Kentucky bluegrass. Further investigation
of why lawns with chinch bugs differ in composition from lawns without
would be useful.

Relatively good Discrimination between chinch bug habitat and chinch
bug non-habitat was given by a discriminant function determined from 1986
thatch thickness and percent Kentucky bluegrass data. When tested with
1986, 1987, and 1988 data the function correctly predicted chinch bug
presence or absence in a lawn in from 63% to 81% of cases. Although the
relationship between chinch bug presence and these two variables can only be
said to be correlative and not cause and effect, the results of the discriminant
function indicate a direction for future research. The discriminant function
may also have practical application as an aid in turf management decisions

regarding preventative treatment or monitoring for chinch bugs.

APPENDICES

 

 

 

APPENDIX 1

Record of Deposition of Voucher Specimens*

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

Voucher Nb.:‘_lgggg7

Title of thesis or dissertation (or other research projects):
The Relationship of Chinch Bug (Blissus leucopterus Hemiptera:
Lygaeidae Presence and Abundance to Parameters of the

Turfgrass Environment

Museum(s) where deposited and abbreviations for table on following sheets:
Entomology Museum, Michigan State university (MSU)

Other Museums:

Investigator's Name (5) (typed)

e
4.;

Maria Geraldine Davis

 

Date August 3, 1989

 

*Reference: Yoshimoto, C. M. 1978. Voucher Specimens for Entomology in
North America. Bull. Entomol. Soc. Amer. 24:141-42.

Deposit as follows:

Original: Include as Appendix 1 in ribbon copy of thesis or
dissertation.

Copies: Included as Appendix 1 in copies of thesis or dissertation.
Museum(s) files. '
Research project files.

This form is available from and the Voucher No. is assigned by the Curator,
Michigan State University Entomology Mbseum.

62

APPENDIX 1.1
voucher Specimen Data

Page ] of ] Pages

 

_~ \HWumn hey u

mmmm m uuzm:q mung

 

 

mumx 9A.; nuns duo/Na: .332?

auwmuo>wc= ouaum sewage“: any as uwmoaov
how acosaooam voumua o>ono osu vo>wooum

 

III!
1|! 1 l

mv>mo oc_upucaw «_cmz

armada .oz nosoao> Avoazuv Amvoemz m.u0umwwumo>cH
Amuammouuc ma mucosa choauwvva away

 

mama mesa om
o m .oo EogmcH mcvmcou .u ":cu.=u_z

mama Apza om
m .ou sogmcu mcvmcnq .u "cam_;upz

mama mean ow
cm .09 snzme~ mcwmcah .m "cam_nupz

mmmfl «and 0m

 

Axmmv maumean mvcouomu

 

coucmucoz maewunooamp mammwpm “w

 

covccucoz szmHn—OU—amp mammwpm

 

 

 

 

 

 

 

 

 

 

 

 

 

 

m m .00 EmnmcH mesmxo ":mm_;owz coucmucoz macmuaouzmp mammwpm
moot vuuumoaov can con: no vouooaaoo coxuu nosuo no muaooam
m e r r m m e .m u measuooam you uumv Hanna
e r o.a e .1 .1 a o. w s
“mwummnwmau
“u w.d.1 .u .A .n n. N" 1“ n.
"no hopes:

 

I 5  ° \l(IHWIHHIIDHIHHHIWNHIM(IIlHHIIIHHHIHW|\|