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Group Title: Research report - North Florida Research and Education Center ; 90-13
Title: Soil fertility effects on population dynamics of soybean insect predators
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Permanent Link: http://ufdc.ufl.edu/UF00066084/00001
 Material Information
Title: Soil fertility effects on population dynamics of soybean insect predators
Series Title: Research report (North Florida Research and Education Center (Quincy, Fla.))
Physical Description: 17 p. : ill. ; 28 cm.
Language: English
Creator: Teare, I. D ( Iwan Dale ), 1931-
Rhoads, Fred ( Frederick Milton )
Funderburk, J. E ( Joseph E. ), 1954-
North Florida Research and Education Center (Quincy, Fla.)
Publisher: North Florida Research and Education Center
Place of Publication: Quincy Fla
Publication Date: 1990
 Subjects
Subject: Insect-plant relationships -- Florida   ( lcsh )
Soybean   ( lcsh )
Genre: bibliography   ( marcgt )
non-fiction   ( marcgt )
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Bibliography: Includes bibliographical references.
Statement of Responsibility: I.D. Teare, F.M. Rhoads, and J.E. Funderburk.
General Note: Cover title.
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Bibliographic ID: UF00066084
Volume ID: VID00001
Source Institution: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: oclc - 71153436

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Full Text







-/3
Soil Fertility Effects on Population Dynamics


of Soybean Insect Predators






I. D. Teare*, F. M. Rhoads, and J. E. Funderburk









SSEP 18 1990

University of Florida









I. D. Teare, Agronomy Dep.; F. M. Rhoads, Dep. of Soils; J. E.
Funderburk, Entomology and Nematology Dep.; North Fla. Res. and
Educ. Ctr. Contribution from the Institute of Food and
Agricultural Sciences, Univ. of Fla. Route 3 Box 4370, Quincy, FL
32351. Research Report NF 90-13.








INTRODUCTION


The vegetation throughout the agrosystem can be selectively

modified by soil fertility to adversely affect pest populations

(Rhoads et al., 1990) and we have found no studies where

beneficial insects [Geocoris spp. (bigeyed bugs), Nabis and

Reduviolus spp. (damsel bugs) and Araneae (spiders)] population

dynamics in soybean were studied in relation to soil fertility.

Large populations of bigeyed bug [Geocoris punctipes (Say)]

occur in soybean fields in the southern U.S. (Shepard et al.,

1974). Bigeyed bugs are predators of Anticarsia gemmatalis

Hubner (Elvin et al.,1983), Nezara viridula (L.) (Crocker and

Whitcomb, 1980), Heliothis zea..Boddie .(Whitconqb and Bell, 1964),

H. virescens, (F.) N(McDaniel and Sterling, 1979), and

Pseudoplusia includes (alker) (Richman et al., 1980).

Reduviolus rosepiennis Reu'ter "i~'"the most common species of

damsel bug comprising over 90% of all individuals occurring in

soybean fields in the Southeast (Dietz et al. 1976). Other

damsel bugs found in soybean are R. alternatus Parshley, R.

americoferus Carayon, Nabidae capsiformis Germar, and N.

deceptivus Harris. Damsel bugs are important predators of

Anticarsia gemmatalis Hubner (Buschman et al., 1977), Heliothis

spp. (McCarty et al., 1980), and Plathypena scabra (F.)
(Sloderbeck and Yeargan, 1983).

Spiders are one of the more abundant groups of arthropods in

the agroecosystem and often outnumber other predaceous insects in

crops (Whitcomb, 1980). Among the many species identified in

2








soybean, Oxyopes salticus Hentz and Chiracanthium inclusum Hentz

are thought to rank first and second, respectively, in seasonal

abundance (Dietz et al., 1976). Oxyopidae (green lynx spiders)

are most common in North Florida. These spiders are found

predominately in the upper zone B as described by Whitcomb

(1980). All spiders are obligate carnivores. The mere fact that

spiders are predators does not mean that they are are entirely

beneficial. Whitcomb (1980) list them as being: 1. primary

consumers of immature and adults of many pest species, 2. natural

enemies of predatory insects (lady beetles, lacewings, etc.), 3.

a food source for other predators and beneficial, 4. competitors

with other predators and beneficial when prey become limiting.

As a result, the same spider species may be beneficial in one

field and pestiferous in another.

Most reports in the literature indicate that populations of

bigeyed bug, damsel bug, and spiders in soybean increase along

with pests and reach greatest densities during mid- or

late-season (Raney and Yeargan, 1977; Deitz et al., 1976; Shepard

et al., 1974; and Pitre et al., 1978; Funderburk and Mack, 1987;

Correa et al., 1977; Mack and Funderburk, 1987; Funderburk et

al.,1988).

Enhancement and conservation of beneficial predators is a

major priority in soybean integrated pest management programs.

Insecticides used to control crop pests may also kill beneficial

predators, and the pest frequently reinvades the field at a

faster rate than beneficial. Pest numbers then build up rapidly

because there are few beneficial predators. Integrated pest
3








management strategies in soybean are designed to use insecticides

only when pest populations reach economically damaging numbers

and even then to selectively use insecticides in ways that reduce

pest populations, but have the least negative impact on predator

populations.

Soil fertilizer operations modify foliage habitats where many

pest and natural enemies reside during at least part of their

life cycle (Rhoads et al., 1990). These modifications can alter

survival or development (Herzog and Funderburk, 1986).

Musick (1985) and Herzog and Funderburk (1986) concluded that

each crop and insect situation must be evaluated individually and

control decisions made for each specific geographical location.

The primary purpose of this study was to determine the effect of

soil fertility on population dynamics and population sizes of

bigeyed bugs, damsel bugs, and spiders in a subsequent soybean

crop following a winter wheat crop. This information should aid

in implementation of cultural control strategies in integrated

pest management programs in relation to soil fertility in a

production systems that conserve natural enemies in soybean field

in the southeastern U.S.

MATERIALS AND METHODS

Soybean were grown on a Norfolk loamy sand (fine, loamy,

siliceous, thermic Typic Kandiudult) at Quincy, FL. Soil samples

were collected from each plot in Feb of each year. This

experiment was conducted in 1986 and 1987 at the North Fla. Res.

and Educ. Ctr. on land which was previously used for fertility

research. Previous soil treatments [P at 0, 27, 54, 107 lb A-
4









applied annually as triple superphosphate for 6 yr; K at 0, 188,

and 375 lb A' applied annually as KCL for 6 yr; N at 0, 60, and

120 lb A-1 each year as ammonium nitrate] are described in Rhoads

and Barnett (1985). Ten cores 1 X 6 inches were taken from each

plot in a criss-cross pattern, composite, air-dried, and ground

to pass a 0.08 inch sieve for analysis. Melich I soil extractant

was used. Soil-test levels (ppm) in relation to treatment code

are shown in Table 1.

Soybean followed wheat in 1986. No P was applied to wheat or

soybean in 1986 because residual levels of P were adequate as

indicated by soil test (Table 1).

Potassium was applied in 1986 as follows:

to wheat K1 = 0, K2 = 84 lb K A- K3 = 168 lb K A-1
-1 -1
to soybean K1 = 0, K2 = 42 lb K A K3 = 84 lb K A

Magnesium was applied in 1986 to wheat only as follows:
1 -1
Mg1 = 0, Mg1 = 60 lb Mg A Mg3 = 120 lb Mg A

Soybean followed snap bean and cabbage in 1987. No P or Mg

was applied to snap bean, cabbage or soybean in 1987.

Potassium was applied in 1987 to soybean only as follows:

to soybean K, = 0, K2 = 42 lb K A1, K = 84 lb K A1.

A 2-row cone planter was used to plant Braxton soybean at a"

planting rate of 40 lb A-1 at 1 inch soil depth on 11 June 1986

and 10 June 1987.

In 1986 and 1987, 1 inch water A-1 was applied preplant and

at intervals during the growing season when tensiometers placed

at 6 inches soil depth reached 0.02 MPa. Insecticides were not

applied at any time during the experiment.

5









Nymphal and adult population densities were estimated on 8

calendar dates/Julian date in 1986 (7-1/182, 7-12/193, 7-23/204,

8-5/217, 8-14/226, 8-26/238, 9-9/252, 9-22/265) and on 7 calendar

dates/Julian date in 1987 (7-8/189, 7-22/203, 8-7/219, 8-18/230,

9-2/245, 9-14/257, 9-29/272). Sampling was begun at early

vegetative stage (V4) and continued until late seed stage (R6) in

both years.

Insect sampling was carried out as described by Irwin and

Shepard (1980) and Whitcomb (1980). All plots were sampled on

each sampling date by beating the plants on both sides of the row

into a 0.9-m square ground cloth placed between the rows. Three

samples were taken per plot on each sampling date. Also,

adjacent plants were searched at their base and the soil surface

was visually examined for bigeyed bug, damsel bug and spiders.

The influence of nutrient level on population densities and

population cycles of bigeyed bug and damsel bug nymphs, and

spiders were evaluated by ANOVA. Data from each growing season

were analyzed separately. The design was a split plot over time.

The main effect compared the influence of soil nutritional level

on seasonal population density. Orthogonal comparisons were used

to define nutrient level differences. The interaction of date X'

treatment compared the influence of soil nutrient level on

seasonal population cycles.
RESULTS AND DISCUSSION

A description of soybean yield in relation to soil fertility

levels of P, K, and Mg in 1986 and 1987 is given in Table 2.

Mean yields were significantly greater for the P P3, and P4
6









levels than the Pi level for both years (1986: F=7.43; df=1,21;

P<0.05 and 1987: F=13.81; df=1,30; P<0.01) but significantly

similar for the P,, P and P4 levels in 1986, but in 1987 P3 and

P4 fertility levels were significantly greater than at the P2

level (F=5.85; df=1,30; P<0.05). Yields were significantly

greater both years for the K, and K, levels than the K level

(1986: F=2.88; df=1,21; P<0.10 and 1987: F=7.34; df=1,30;

P<0.01), with yields similar for the K2 and K, levels. Yields

were not significantly affected by Mg fertility levels in 1986

and 1987.

Insect data for individual treatments are reported in terms

of population densities and cycles which, when combined over

date, describe seasonal population dynamics (Fig. 1, 2, 3, 4).

Population densities are described in terms of daily and seasonal

variation. Population cycles are recognized in figures in

relation to insect numbers and stage, and date or plant

physiological stage.

Population densities of damsel bug nymphs (DBN) were very low

each year until soybean Growth Stage R4; then, densities

increased in all treatments until R6 in 1986 and R5 in 1987.

Population densities of DBN differed between fertility treatments"

in 1986 (F=2.4; df=7,21; P<0.06) but in 1987 was nonsignificant.

Orthogonal comparisons were used to separate the effects of P, K,

Mg levels on DBN population densities. Estimates were similar

for P4 and P, in 1986,but P3 was greater than P2 and P, levels

(F=13.0; df=1,21; P<0.01) (Fig. 1). Population cycle increases








were earlier in 1986 according to fertilizer treatment,

P4>P,>P2>P

Orthogonal comparisons revealed that density estimates of DBN

were not significantly affected by K or Mg in 1986 or 1987.

The population densities of bigeyed bug nymphs (BBN) differed

between fertility treatments in 1986 (F=2.3; df=7,21; P<0.07) and

1987 (F=3.3; df=10,30; P<0.01). Orthogonal comparisons were used

to separate the effects of P, K, and Mg levels on BBN population

densities. Density estimates were significantly affected by P

levels. Population cycles of BBN for treatments at different

levels of P, but constant levels of K and Mg, are shown in Figure

2 to illustrate the effect of P on density estimates. Mean

densities were significantly greater in treatments at the P4

level compared with densities in treatments at the P P and P3

levels in 1986 (F=6.0; df=l,21; P<0.05)and in 1987 (F=6.5;

df=10,30; P<0.05). Mean densities also were significantly

greater in treatments at the P3 level than in treatments at the

P1 and P2 levels in 1986 (F=7.8; df=1,21; P<0.05), but not

significant in 1987.

Density estimates of BBN were significantly affected by Mg in

1987 (Fig. 3), but not in 1986. Population cycles of BBN for'

treatments at different levels of Mg, but constant levels of P

and K are shown in Figure 3. Orthogonal treatment comparisons

were used to show that estimates in 1987 were significantly

greater in treatments at the Mg2 and Mg, levels than at the Mg,

level (F=6.4; df=1,30; P<0.05), with estimates significantly

different between the Mg2 and Mg3 levels (F=12.8; df=1,30;

8









P<0.01). Orthogonal comparisons also revealed that BBN estimates

were not significantly affected by K levels in 1986 or 1987 (data

not shown).

The treatment x date interaction was used to determine if

fertilizer treatment influenced population cycles. This

interaction was significant for VBC in 1986 (F=1.53; df=49,168;

P<0.05) and not in 1987.

The density estimates of spiders differed between .fertility

treatments in 1986 (F=3.3; df=7,21; P<0.05), but not in 1987.

Population cycles of spiders at different levels of P, but

constant levels of K and kg, are shown in Figure 4. Orthogonal

treatment comparisons revealed that density estimates were

affected by P levels. Mean densities were significantly greater

at the P4 level than at the P,, P2, and P3 levels (F=3.1;

df=1,21; P<0.10) and at the P3 level than at the P2 and P1 levels

(F=14.9; df=1,21; P<0.01).

Orthogonal comparisons revealed that density estimates of

spiders were not significantly affected by K or Mg in 1986 and

1987 (data not shown).

Fertility levels of P, therefore, affected population

dynamics of DBN, BBN, and spiders. In 1986, increased fertility-

levels of P that did not result in a significant yield increase

did result in significant increases in beneficial insect

population densities, but in 1987 significant increases were only

observed in BBN population densities. Although yields were

statistically similar at the P2 P3, and P4 levels, population

densities of DBN were significantly increased from P2 to P3 (P3
9









similar to P ) in 1986 and population densities of BBN were

significantly increased from P3 to P4 in both years and P2 to P3

in 1986.

Population densities of DBN, BBN, and spiders in 1986 and

1987 were not significantly affected by K levels, even at levels

significantly affecting soybean yield.

Although Mg levels sometimes affected soybean yield, pest

population densities were only significantly influenced by Mg

levels on population densities of BBN in 1987.

The reason why soil fertility levels affected population

dynamics of these major\ beneficial is unexplained. Soil

fertility level may be directly affecting pest populations

through alterations in crop growth or nutritional level (Rhoads

et al., 1990) and indirectly affecting important natural enemies

of the pests, such as bigeyed bugs, damsel bugs, and spiders.

Our results showing effects of soil fertility on population

dynamics of the major beneficial of soybean in the extreme

southern U.S. are useful for integrated pest management programs

in the region. Current recommendations for soil fertility levels

necessary to obtain optimal soybean yields should be followed

closely. In addition to reducing the cost of fertilizer, it will

also reduce the likelihood of pest outbreak and the need for

additional costs associated with pest control.








REFERENCES
Adkisson, P.L. 1958. The influence of fertilizer applications
on population of Heliothis zea (Boddie), and certain insect
predators. J. Econ. Entomol. 51:757-759.
Buschman, L.L., W.H. Whitcomb, R.C. Hemenway, D.L. Mays, Nguyen
Ru, N.C. Leppla, and B.J. Smittle. 1977. Predators of
velvetbean caterpillar eggs in Florida soybean. Environ.
Entomol. 6:403-407.
Correa, B.S., A.R. Pannizzi, G.G. Newman, and S.G. Turnipseed.
1977. Distribuicao geografica e adundancia estacional dos
principals insectos-pragas da soja e seus predadores. An.
Soc. Entomol. Brasil 6:40-50.
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.M.
Brooks, and R.E. Stinner. 1976. A guide to the
identification and biology of soybean arthropods in North
Carolina. N.C. Agric. Exp. Sta. Bull. 238. 264 pp.
Elvin, M.K., J.L. Stimac,\and W.H. Whitcomb. 1983. Estimating
rates of arthropod predation on velvetbean caterpillar larvae
in soybeans. Fla. Entomol. 66:230-330.
Funderburk, J.E., and T.P. Mack. 1987. Abundance and dispersion
of Geocoris spp. (Hemiptera:Lygaeidae) in Alabama and Florida
soybean fields. Fla. Entomol. 70:432-439.
Funderburk, J.E, and T.P. Mack. 1989. Seasonal abundance and
dispersion patterns of damsel bugs (Hemiptera:Nabidae) in
Alabama and Florida soybean fields. J. Entomol. Sci. 24:9-15.
Funderburk, J.E., D.L. Wright, and I.D. Teare. 1988. Preplant
tillage effects on Population dynamics of soybean insect
predators. Crop Sci. 28:973-977.
Herzog, D.C., and J.E. Funderburk. 1986. Ecological bases for
habitat management and cultural control. In: M. Kogan (ed.)
Ecological theory and integrated pest management practice.
Wiley Interscience, N.Y. p. 217-250.
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
32-P. Environ. Entomol. 8:1083-1087.
McCarty, M.T., M. Shepard, and S.G. Turnipseed. 1980.
Identification of predaceous arthropods in soybeans using
autoradiography. Environ. Entomol. 9:199-203.
Musick, G.J. 1985. Management of arthropod pests in con-
servation-tillage systems in the southeastern U.S. p.
191-204. In: W.L. Hargrove, F.C. Boswell, and G.W. Langdale
(ed.) Proceedings of the 1985 southern region no-till
conference. July 16-17, 1985. Griffin, Ga.







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., abd K.V. Yeargan. 1977. Seasonal abundance of
common phytophagous and predaceous insects in Kentucky
soybeans. Trans. Ky. Acad. Sci.38:83-87.
Rhoads, F.M. 1990. Soil fertility effects on soybean yield in
the Southeast. Univ. of Fla. Res. and Educ. Ctr.. Quincy,
FL, Res. Rep. NF-90-14. p. 1-10.
Rhoads, F.M., and R.D. Barnett. 1985. Nutritional requirement of
high yield cropping systems in the Southeast. Annual Report,
IFAS, Quincy, FL. Potash and Phosphate Institute, Atlanta,
Ga.
Richman, D.B., R.C. Hemenway, and W.H. Whitcomb. 1980. Field
cage evaluation of predators of the soybean looper,
Psuedoplusia includes (Ledidoptera:Noctuidae). Environ.
Entomol. 9:315-317.
Shepard, M., G.R. Carner, and S.G. Turnipseed. 1974. Seasonal
abundance of predaceous arthropods in soybeans. Environ.
Entomol. 3:985-988.
Sloderbeck, P.E., and K.V. Yeargan. 1983. Comparison of Nabis
americoferus and Nabis roseipennis (Hemiptera: Nabidae) as
predatorof the green cloverworm (Lepidoptera:Noctuidae).
Environ. Entomol. 12:161-165.
Whitcomb, W.H., and K. Bell. 1964. Predaceous insects, spiders
and mites of Arkansas cotton fields. Ark. Agric. Exp. Stn.
Bull. 690:1-84.
Whitcomb, W.H. 1980. Sampling spiders in soybean fields. In M.
Kogan and D.C. Herzog (Ed.) Sampling methods in soy-ean
entomology. Springer-Verlag, N.Y. p.544-558.

ACKNOWLEDGEMENTS
Our thanks to E. Brown, Senior Laboratory Technician; A.
Brown, Agricultural Supervisor; A. Manning, Biological
Scientist II; North Fla. Res. and Educ. Ctr., Univ. of Fla.
Quincy FL 32351; for data anaylsis and illustration, data
collection, and plot preparation and management.










Table 1. Soil tests for use in soybean-fertility-pest experiment


in 1986 and 1987 at Quincy FL.




Soil-test levels (ppm) across reps.


P, = 10
K = 31
Mg, = 40

PI = 7
1
K, = 32
Mg, = 33


P = 21
K2 = 55
Mg2 = 89

P2 = 15
K2 = 65
Mg2 = 50


P3 = 35
3
K3 = 73
Mg3 = 71

P = 33
3
K3 = 81
Mg3 = 47


P4 = 82



P = 75
4


Table 2.



Year


Soybean yields (bu/A) in relation to fertility treatment
and year with no pesticide treatment, Quincy FL.


Soybean yield (bu/A) for fertility treatments across reps.


P, = 10
K = 17
Mg1 = 20

P, = 10
K, = 13
Mgi = 16


P2 = 22
K2 = 20
Mg2 = 25

P2 = 14
K2 = 17
Mg2 = 20


P3 = 25
K = 25
Mg, = 28

P = 20
K, = 20
Mg9 = 18


Year

1986



1987


1986



1987


P4 = 25



P4 = 17

















R1R2 R4 R5 R6 R6


0
oe


u- M R 1 W i I I i I I 0 --
180 189 203 217 226 238 252 285 275 285 180


Day of Year


Figure 1.


Mean population density of damsel bug nymphs in relation to
day of year (Days Julian, 1986 and 1987) and physiological
stage of soybean development in treatments differing in soil
fertility levels of P, but at the same level of K and Mg.


189 203 217 228 238 252 285 275 285


V3 V5.5 R1 R2


R4 R5 R6 R6


V3 V5.5















R4 R5 R6 R6


R3 R4 R5


0
0:

I -


180 189 203 217 226 238 252 265 275 285


180 189
180 189


Day of Year


Figure 2.


Mean population density of bigeyed bug nymphs in relation to
day of year (Days Julian, 1986.and 1987) and physiological stage
of soybean development in treatments differing in soil
fertility levels of P, but at the same level of K and Mg.


203 217 226 238 252 265 275 285


V3 V5.5 R1 R2


V4 R1.5


R6 R6
















R3 R4 R5 R6 R6


203 217 226 238


265 275 285


1987










p 1 3 3K



30 189 203 217 226 238 252 265 275 285


Day of Year


Mean population density of bigeyed bug nymphs in relation to
day of year (Days Julian, 1986 and 1987) and physiological
stage of soybean development in treatments differing in soil
fertility.levels of Mg, but at the same level of P and K.


0
1or
T-
'E







>O
(D
0)
M


5
1986
4


3




2 3
2 MgIPI K3

Mg 2-K--


0 f ^ -- -- i -- | -- | -- --I -1 l --


180 189


Figure 3.


R4 R5 R6 R6


V4 R1-2


V3 V5.5 R1 R2














R3 R4 R5 R6 R6


180 189 203 217 228 238 252 265 275


-- o--- '-
285 180 189


203 217 226 238 252 265 275 285


Day of Year


Mean population density of spiders in relation to day of year
(Days Julian, 1986 and 1987) and physiological stage of
soybean development in treatments differing in soil fertility
levels of P, but at the same level of K and Mg.


Figure 4.


V3 V5.5 R1 R2


R4 R5 R6 R6


V4 R1.5




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