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Group Title: Research report - North Florida Research and Education Center ; 87-9
Title: Bigeyed bug abundance and dispersion patterns of geocoris spp. (hemiptera lygaeidae) in soybean fields
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 Material Information
Title: Bigeyed bug abundance and dispersion patterns of geocoris spp. (hemiptera lygaeidae) in soybean fields
Series Title: Research report (North Florida Research and Education Center (Quincy, Fla.))
Physical Description: 12 p. : ill. ; 28 cm.
Language: English
Creator: Funderburk, J. E ( Joseph E. ), 1954-
Mack, T. P
North Florida Research and Education Center (Quincy, Fla.)
Publisher: North Florida Experiment Station
Place of Publication: Quincy Fla
Publication Date: 1987
 Subjects
Subject: Geocoris -- Population   ( lcsh )
Genre: bibliography   ( marcgt )
non-fiction   ( marcgt )
 Notes
Bibliography: Includes bibliographical references.
Statement of Responsibility: by J.E. Funderbruk and T.P. Mack.
General Note: Caption title.
 Record Information
Bibliographic ID: UF00066064
Volume ID: VID00001
Source Institution: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: oclc - 71051979

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Full Text
/0J


8''7-4


/Contribution from the Inst. of Food and Agric. Sci. Florida Exp. Stn., Univ.

of Florida, and the North Florida Res. and Educ. Ctr., Quincy, FL 32351.

Research Report NF 87-9.

a/Assistant Professor of Entomology, Univ. of Florida and Professor of

Entomology, Auburn Univ. 36849-4201.


Y-'


I


? Central Science
Bigeyed Bug Abundance and Dispersion Patterns of Geocons Scien

(Hemiptera: Lygaeidae) in Soybean Fields'
I SEP 23 1987
J. E. Funderburk and T. P. Mack!-/

ABSTRACT Universty of Florida

Seasonal abundance and dispersion characteristics of adult and nymphal

Geocoris spp. (bigeyed bug) populations were determined for soybean fields

located in Alabama and Florida. Three fields were sampled in 1985 and two

fields were sampled in 1986. Populations were present in each field from

middle or late vegetative stages of crop growth until crop senescence.

Numbers increased through the growing season and were greatest on the last or

near the last sample dates. At least three complete and additional partial

generations were typical, with populations of different generations broadly

overlapping. Population dynamics were similar to previously reported data in

other states in the southern U.S., indicating a similar phenology for bigeyed

bugs in soybean fields throughout the region. Dispersion statistics of

variance/mean ratio and Taylor's power law were calculated for adult and

nymphal sample estimates. Populations of nymphs were always aggregated.

Adults usually were randomly distributed, but sometimes aggregated.









Geocoris spp. (bigeyed bugs) are common, polyphagous insect predators in

many crops. Populations of Geocoris punctipes (Say) occur in large numbers in

soybean fields in the southern U.S. (Tugwell et al. 1973, Turnipseed 1972,

Shepard et al. 1974). The diet of arthropod prey is supplemented with some

feeding on plants, which improves survival and decreases developmental time

(Naranjo and Stimac 1985). The predator is an important biological control

agent of Anticarsia gemmatilis Hubner (Elvin et al. 1983) and Nezara viridula

(L.) (Crocker and Whitcomb 1980), which are the most economically important

pests of soybean. Bigeyed bugs may be important agents in the suppression of

populations of occasional pests of soybean, such as Heliothis zea Boddie

(Whitcomb and Bell 1964), H. virescens, (F.) (McDaniel and Sterling 1979),

Pseudoplusia includes (Walker) (Richman et al. 1980), and many others.

The population dynamics of bigeyed bugs in soybean fields has been found

to vary according to geographical location. Numbers were greatest in late

August to early September in Kentucky (Raney and Yeargan 1977), early August

or mid-September in North Carolina (Deitz et al. 1976), late September in

South Carolina (Shepard et al. 1974a), and between late June and early August

in Mississippi (Pitre et al. 1978). More than one generation occurred in each

case, as populations were present during most of the growing season. No

published information exists on the population dynamics of bigeyed bugs in

soybean in more southerly areas of the southern U.S. growing region.

The dispersion characteristics of bigeyed bug populations in South

Carolina soybean fields were investigated by Waddill et al. (1974).

Populations were randomly distributed on most sample dates, fitting the

Poisson distribution. Pieters and Sterling (1973) reported that their

populations in cotton were clumped on most occasions, fitting the negative

binomial. Dispersion characteristics of insect populations have been shown to









vary with population density and sample-unit size (Wilson and Room 1982,

1983). Therefore, additional information taken over a range of population

densities and at a different sample-unit size from the Waddill et al. (1974)

study would provide valuable information about the dispersion characteristics

of their populations in soybean.

The primary purpose of the present study was to determine the temporal

abundances of bigeyed bug populations in soybean in Alabama and Florida.

Their dispersion characteristics over a range of population densities also

were quantified. Such information will allow for implementation of pest

management practices that conserve these natural control agents in soybean

fields.

Materials and Methods

Bigeyed bug populations were monitored over two cropping seasons in

soybean fields located in Florida and Alabama. Each was a production field

that was grown in a manner typical for the agroecosystem, but none were

treated with an insecticide that would directly affect bigeyed bug

populations. Fields were disked before planting, with no subsoiling.

Planting dates ranged from late May to late June. Bigeyed bug nymphal and

adult populations were monitored in three fields in 1985. All fields were in

different counties of Alabama, which were Dallas, Elmore, and Henry counties

(Fig. 1). Nymphal and adult populations were monitored in two fields in 1986.

One field was located in Dallas Co., Alabama and the other in Gadsden Co.,

Florida (Fig. 2). All fields were at least 2 ha in area. -Soybean varieties

were 'Tracey M' for the Alabama fields and 'Braxton' for the Florida field.

Nymphal and adult population density was estimated ca. weekly within each

field. Sampling was begun at the early vegetative crop-growth stages and

continued to the late seed stages of crop growth. An exception was the Dallas









Co., Alabama field sampled in 1986. There, extreme drought resulted in

retardation of plant growth, and sampling was discontinued in mid-August.

Each field was divided into 12 parts of equal area, and four random samples

taken within each.

Sampling procedures were according to those established in previous

studies as being most appropriate for estimating nymphal and adult bigeyed bug

populations in soybean (Rudd and Jensen 1977, Shepard et al. 1974b, Turnipseed

1974). Descriptions of methods for sampling their populations in soybean are

contained in Irwin and Shepard (1980). The ground cloth method was employed.

Forty-eight, 1.8-m samples were taken in each field on each sample date when

their populations were in detectable numbers. This sample-unit size differed

from the 1.2-m size in the Waddill et al. (1974) study. For each sample, the

ground cloth was laid between two rows, the soybean plants from both sides

(0.9 m on each side) beaten onto the cloth, and the number of nymphs and

adults determined. Also, bases of the plants and adjacent soil were examined

for any bigeyed bugs.

The variance/mean ratio was calculated for adult and nymphal sample

counts on each sample date in each field (Southwood 1978). These analyses

were performed by using Myers' (1978) FORTRAN program. Log-transformed means

and variances of adult and nymphal sample counts then were calculated for each

sample date in each field, and Taylor's (1984) power law relationship for each

field determined. A Taylor's power law relationship also was determined for

each year by combining data from all fields sampled in that year. All

Taylor's relationships were determined by using SAS programs (SAS Institute

1982a,b).









Results
The mean numbers (+SE) of adult and nymphal bigeyed bugs on each sample

date in each soybean field sampled in 1985 and 1986 are shown in Figs. 1 and

2, respectively. Overall precision of the sampling program, as determined by

the SE values, was excellent. The SE was rarely over 25% of the mean except

when populations were very small. Populations of bigeyed bugs were present in

all soybean fields during most of the growing season. Nearly all of the

bigeyed bugs in all fields was G. punctipes, but G. uliginosis was noted in

very small numbers (i.e., < 5% of total).

Adults were first detected in the fields during middle to late vegetative

soybean growth stages. The size of adult populations at this time was never

great. Usually, nymphal populations appeared about a week or two later. Both

adult and nymphal populations then were present in substantial numbers during

the rest of the growing season in all but one of the fields. Adult and

nymphal populations did not occur in large numbers in that field until late in

the growing season. In nearly all fields, generational cycles were indicated

by peaks in nymphal populations ca. every 30 days. There was considerable

overlap between the generations in all fields, because the number of bigeyed

bugs rarely declined greatly in magnitude. Population size was small in the

1985 Henry Co. and 1986 Dallas Co., Alabama fields, compared to the other

fields sampled in this study. The drought may be the reason for the lower

populations in 1986 Dallas Co., Alabama field.

Population size varied among fields, but population trends were similar.

At least 3 complete generations occurred, with additional partial generations

also present. The number of bigeyed bugs increased through the growing

season, with numbers usually greatest on the last or near the last sample

date.








9
8 HENRY CO., AL NYMPHS
7 .*.-" ELMORE CO., AL
---DALLAS CO., AL
6 -

0 ...... --



C3 ADULTS
z
0-
I I I ,





6/18 6/28 7/8 7/18 7/28 8/7 8/17 8/27 9/6 9/16 9/26
1985 SAMPLE DATE


Fig. 1. Mean numbers (+SE) of adult and nymphal Geocoris spp.
-populations in three soybean fields sampledin 1985
(Dallas, Elmore, and Henry Cos., Alabama).
0-0 .-^L----^'_----.l------'r-"












(Dallas, Elmore, and Henry Cos., Alabama).


2


0
6/


NYMPHS
........ GADSDEN CO., FL
DALLAS CO., A

1*- .* II


... .I ............ ....... .A UL

JI ADULTS



: !-i---.1-- ....tI....1...--.i. .--tt...
l" I I ,I


/13


7/23


8/12


9/1 9/21 10/11


1986 SAMPLE DATE


Fig. 2. Mean numbers (+SE) of adult and nymphal Geocoris spp.
populations in two soybean fields sampled in 1986
(Dallas Co., Alabama and Gadsden Co., Florida).


I










For each sample date in the 1985 and 1986 soybean fields, the

variance/mean ratio of adult and nymphal populations are presented in Table 1.

Variance/mean ratios of <1, 1, and >1 represent uniform, random, and clumped

distributions, respectively (Southwood 1978). According to this measure of

dispersion, nymphal populations were aggregated on 55.8% of the field/date

data sets when data were sufficient for analysis. Adult populations were

aggregated 47.1% of the time. Values were >1, but not significantly greater

than 1, on most other dates for both nymphs and adults.

Taylor's power law relates variance (s2) to mean density (m) by the

relationship, s2 = amb. Taylor et al. (1978) considered the slope (b) to be a

constant for a species (with values of bl indicating uniform,

random, and clumped distributions, respectively) and the intercept (a) to be

reflected by sample-unit size. Taylor's power law is a particularly useful

dispersion index, because it allows for a description of a species

distribution pattern as changing with density.

Regression statistics of Taylor's power law relationships for bigeyed bug

nymphal and adult sample estimates for each soybean field and for each year

are shown in Table 2. For all relationships involving nymphal populations, b

was statistically > 1(P < 0.05) according to t tests. These values of b and

the relatively high r2-values (mean = 0.94 and 0.94 for 1985 and 1986,

respectively) indicate that bigeyed bug nymphal populations were aggregated

over a wide range of population densities. Results were less definitive for

adult populations, with b statistically > 1 for 1 field. For 3 fields, b was

very near 1, strongly indicating a random distribution. The precision of the

regression relationships was good, with mean r2-values of 0.76 and 0.74 for

1985 and 1986, respectively.










Table 1. Variance/tean ratios of nymphal and adult Geocoris spp. populations
in Henry, Elmore, and Dallas Cos., AL and Gadi-en Co., FL.


SAMPLE s2/ SAMPLE s2 /
DATE NYMPHS ADULTS DATE NYMPHS ADULTS


1985 DALLAS CO., AL
22 Aug. 1.02
5 Sept. 1.69*
13 Sept. 1.34*
17 Sept.

1985 ELMORE CO., AL


21 June
28 June
3 July
11 July
19 July
24 July
1 Aug.
8 Aug.
16 Aug.
19 Aug.
30 Aug.
9 Sept.
16 Sept.

1985
24 June
1 July
8 July
15 July
22 July
29 July
6 Aug.
13 Aug.
20 Aug.
27 Aug.
10 Sept.


1.32*
1.24
1.17
1.43*
1.26
1.53*
1.76*
1.83*
2.01*
2.90*
3.65*

HENRY CO., AL
1.87*


1.28
1.34*
1.06
1.12
1.25
1.67*
3.14
1.11


16 June
24 June
30 June
7 July
14 July
21 July
28 July
4 Aug.
11 Aug.
18 Aug.
25 Aug.
2 Sept.
8 Sept.
17 Sept.
24 Sept.
3 Oct.


2.47
1.32
1.68*
1.45*


1.48*
1.43*
1.60*
1.09
0.94
0.63
1.88*
1.68*
1.45*
1.51*
1.59*
0.94
1.51*



1.37*
1.35*
1.33
0.73
1.49*
1.29
0.96
1.17
1.24
1.47*


1986 GADSDEN CO., FL



1.06
1.11
2.04*
2.97*
1.96*
1.63*
1.41*
1.36*
1.23
1.37*
4.08*
2.07*
0.99


1986 DALLAS CO.,


0.97
1.16
1.20
1.23
1.34
1.09


*Significantly different than l(P < 0.05) by X2 test.


Table 2. Regression statistics of Taylor's power law relationships for
nymphal and adult sample data in the 1985 and 1986 soybean fields
(Henry, Elmore, and Dallas Cos., Alabama and Gadsden Co., Florida).
(All relationships are significantly linear beyond the 0.01 level
and no intercept is significantly different from 0 according to a
students t test.)


NYMPHS ADULTS
FIELD AND YEAR INTERCEPT SLOPE r2 INTERCEPT SLOPE r


DALLAS CO., AL 1985 -0.02 1.59* 0.95 -0.01 1.63 0.74

ELMORE CO., AL 1985 -0.05 1.40* 0.98 0.05 0.95 0.59

HENRY CO., AL 1985 -0.02 1.25* 0.89 -0.01 1.22* 0.94

ALL FIELDS 1985 -0.02 1.33* 0.96 0.01 1.16* 0.96

DALLAS CO., AL 1986 0.00 1.16* 0.99 0.01 0.98 0.79

GADSDEN CO., FL 1986 -0.07 1.43* 0.88 0.09 0.89 0.68

ALL FIELDS 1986 -0.04 1.40* 0.93 0.03 1.07 0.86


*Significantly > 1 (P < 0.05) according to a t test


0.97
1.10
0.72
1.05
1.16
1.64*
1.32
2.34
1.02
1.33
1.57*
1.00
1.66*
1.67*
0.92
1.19


1.22
1.11

1.06
1.23
1.06
1.23
1.23







Discussion
Bigeyed bugs typically were common throughout most of the growing season

in the soybean fields sampled in our study, with greatest population densities

occurring near the end of the growing season. These results from Alabama and

Florida are similar to previously published studies conducted in other states

in the southern U.S. (Raney and Yeargan 1977, Dietz et al. 1976, Shepard et

al. 1974a, Pitre et al. 1978). Bigeyed bugs apparently have a similar

phenology in soybean throughout the region. Bigeyed bugs obviously are

important, indigenous natural enemies of soybean pests in the southern U.S.

Enhancement and conservation of their populations should be a major priority

in soybean IPM programs.

Nymphal populations were clumped in the fields sampled in this study,

which contrasts with the conclusion drawn by Waddill et al. (1974) that

populations were random and best described by the poisson distribution.

Differences between the studies may indicate that dispersion characteristics

of bigeyed bug nymphs change as a function of population density and/or

sample-unit size. However, our results from a wide-range of densities in a

number of fields over two growing seasons would be a strong indication that

clumping is typical for nymphal populations. Adult populations usually were

randomly distributed, but sometimes clumped. These results corroborate the

conclusions drawn by Waddill et al. (1974) that their populations are best

described as randomly distributed.







LITERATURE CITED

Crocker, R. L., and W. H. Whitcomb. 1980. Feeding niches of the big-eyed bugs

Geocoris bullatus, G. punctipes, and G. uliginosus (Hemiptera:

Lygaeidae:Geocorinae). Environ. Entomol. 9:508:513.

Deitz, L. L., J. W. Van Duyn, J. R. Bradley, Jr., R. L. Rabb, W. H. Brooks,

and R. E. Stinner. 1976. A guide to the identification and biology of

soybean arthropods in North Carolina. North Carolina Agric. Exp. Sta.

Bull. 238. 264pp.

Elvin, M. K., J. L. Stimac, and W. H. Whitcomb. 1983. Estimating rates of

arthropod predation on velvetbean caterpillar larvae in soybeans. Fla.

Entomol. 66:320-330.

Irwin, M. E., and M. Shepard. 1980. Sampling predaceous hemiptera on soybean,

pp. 505-531. In: M. Kogan and D. C. Herzog (ed.) Sampling Methods in

Soybean Entomology. Springer-Verlag, Inc. New York.

McDaniel, S. G., and W. L. Sterling. 1979. Predator determination and

efficiency on Heliothis virescens eggs in cotton using 2P. Environ.

Entomol. 8:1083-1087.

Myers, J. H. 1978. Selecting a measure of dispersion. Environ. Entomol.

7:619-621.

Naranjo, S. E., and J. L. Stimac. 1985. Development, survival, and

reproduction of Geocoris punctipes (Hemiptera: Lygaeidae): Effects of

plant feeding on soybean and associated weeds. Environ. Entomol.

14:523-530.

Pieters, E. P., and W. L. Sterling. 1973. Inferences on the dispersion of

cotton arthropods in Texas. Environ. Entomol. 2:863-867.

Pitre, H. N., T. L. Hillhouse, M. C. Donahoe, and H. C. Kinard. 1978.

Beneficial arthropods on soybean and cotton in different ecosystems in

Mississippi. Miss. Agric. For. Exp. Sta. Tech. Bull. 90. 9pp.








Raney, H. G., and K. V. Yeargan. 1977. Seasonal abundance of common

phytophagous and predaceous insects in Kentucky soybeans. Trans. Ky.

Acad. Sci. 38:83-87.

Richman, D. B., R. C. Hemenway, and W. H. Whitcomb. 1980. Field cage

evaluation of predators of the soybean looper, Psuedoplusia includes

(Lepidoptera:Noctuidae). Environ. Entomol. 9:315-317.

Rudd, W. G., and R. L. Jensen. 1977. Sweep net and ground cloth sampling for

insects in soybean. J. Econ. Entomol. 70:301-304.

SAS Institute. 1982a. SAS user's guide: statistics. SAS Institute, Cary, N. C.

1982b. SAS user's guide: basics. SAS Institute, Cary, N. C.

Shepard, M., G. R. Corner, and S. G. Turnipseed. 1974a. Seasonal abundance of

predaceous arthropods in soybeans. Environ. Entomol. 3:985-988.

Shepard, M., G. R. Carner,.and S. G. Turnipseed. 1974b. A comparison of three

sampling methods for arthropods in soybeans. Environ. Entomol. 3:227-232.

Southwood, T. R. E. 1978. Ecological methods, 2nd ed. Wiley, New York.

Taylor, L. R., I. P. Woiwood, and J. N. Perry. 1978. The density dependence of

spatial behavior and the rarity of randomness. J. Anim. Ecol. 47:383-406.

Taylor, L. R. 1984. Assessing and interpreting the spatial distributions of

insect populations. Annu. Rev. Entomol. 29:321-357.

Tugwell, P., E. P. Rouse, and R. G. Thompson. 1973. Insects in soybeans and a

weed host (Desmodium sp.). Ark. Agric. Exp. Stn. Rep. Ser. 214. 18pp.

Turnipseed, S. G. 1972. Management of insect pests of soybean. Proc. Tall

Timbers Conf. Econ. Anim. Control Habitat Manage. 1:189-203.

Turnipseed, S. G. 1974. Sampling soybean insects by various D-Vac, sweep, and

ground cloth methods. Fla. Entomol. 57:219-223.

Waddill, V. H., B. M. Shepard, S. G. Turnipseed, and G. R. Carner. 1974.

Sequential sampling plans for Nabis spp. and Geocoris spp. in soybeans.

Environ. Entomol. 3:415-419.








Whitcomb, W. H., and K. Bell. 1964. Predaceous insects, spiders and mites of

Arkansas cotton fields. Ark. Agric. Exp. Stn. Bull. 690:

1-84.

Wilson, T. P., and P.M. Room. 1982. The relative efficiency and reliability of

three methods for sampling arthropods in Australian cotton fields. J.

Aust. Entomol. Soc. 21:175-181.

and 1983. Clumping patterns of fruit and arthropods in cotton

with implications for binomial sampling. Environ. Entomol. 12:50-54.




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