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Group Title: Research report - North Florida Research and Education Center ; 90-12
Title: Soil fertility effects on population dynamics of soybean insect pests
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Permanent Link: http://ufdc.ufl.edu/UF00066082/00001
 Material Information
Title: Soil fertility effects on population dynamics of soybean insect pests
Series Title: Research report (North Florida Research and Education Center (Quincy, Fla.))
Physical Description: 12 pages : ill. ; 28 cm.
Language: English
Creator: Rhoads, Fred ( Frederick Milton )
Funderburk, J. E ( Joseph E. ), 1954-
Teare, I. D ( Iwan Dale ), 1931-
North Florida Research and Education Center (Quincy, Fla.)
Publisher: North Florida Experiment Station
Place of Publication: Quincy Fla
Publication Date: 1990
 Subjects
Subject: Soil fertility -- Florida   ( lcsh )
Soybean -- Diseases and pests -- Florida   ( lcsh )
Soybean -- Diseases and pests -- Identification   ( lcsh )
Insect pests -- Identification   ( lcsh )
Genre: bibliography   ( marcgt )
non-fiction   ( marcgt )
 Notes
Bibliography: Includes bibliographical references.
Statement of Responsibility: F. M. Rhoads, J.E. Funderburk, and I.D. Teare.
General Note: Caption title.
 Record Information
Bibliographic ID: UF00066082
Volume ID: VID00001
Source Institution: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: oclc - 71153163

Table of Contents
    Title Page
        Page 1
    Main
        Page 2
        Page 3
        Page 4
        Page 5
        Page 6
        Page 7
    Reference
        Page 8
        Page 9
        Page 10
    Tables
        Page 11
    Figures
        Page 12
Full Text

(63brl,


Soil Fertility Effects on Population Dynamics

of Soybean Insect Pests






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








Ce'tra! Science
Library

171MAY 29 1990

;ivi'ersity of Florida






J. E. Funderburk, Entomology and Nematology Dep.; I. D. Teare, Agronomy Dep.;

and F.M. Rhoads, Soils 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 90-12.




'5,


INTRODUCTION
The use of fertilizers can influence the injury to a crop from arthropod

pests, through alterations in crop growth or nutritional levels (Herzog and

Funderburk, 1986). Many cotton pests are affected by soil fertility levels.

Enhancement of succulent cotton growth through fertilization renders the crop

more attractive to populations of the cotton aphid, Aphis gossypii Glover

(McGarr, 1942, 1943); the cotton fleahopper, Pseudamatamoscelis seriatus

(Reuter) (Adkisson, 1957); and the cotton bollworm, Heliothis zea (Adkisson,

1958). In short-season production areas, increasing levels of soil fertility

delay the fruiting period of the crop, thereby reducing the potential for

escape from boll weevil, Anthonomus grandis Boheman, injury (Walker et al.,

1976, 1977).

Soil fertility effects upon soybean [Glycine max (L.) Merr.] yield

(Rhoads and Barnett, 1990) have been reported for the Southeast, but the

influence of soil fertility on soybean insect pests has not been documented.

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

pest situation must be evaluated individually and pest control decisions made

for each specific geographical location. The purpose of this study was to

determine the effect of soil fertility on population dynamics of several

foliage-inhabiting soybean pests, including larval velvetbean caterpillars

(VBC), Anticarsia gemmatalis (Hubner), and nymphal and adult southern green

stink bugs (SGSB), Nezara viridula (L.). These findings should aid in

implementation of cultural control strategies for these major insect pests of

soybean in the southeastern U.S.









:MATERIALS AND METHODS
Soybean were grown on a Norfolk loamy sand (fine, loamy, siliceous,

thermal 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, 25, 50, 100 lb. AI

applied annually as triple superphosphate for 6 yr; K at 0, 190, and 380 lb.

A applied annually as KCL for 6 yr; N at 0, 50, and 100 each year as

ammonium nitrate] are described in Rhoads and Barnett (1985). Each year of

the experiment, ten cores (1 X 6 inch) were taken from each plot in a

criss-cross pattern, composite, air-dried, and ground to pass a 0.1 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

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 AI, K, = 166 lb. K A1;

to soybean K1 = 0, K2 = 42 lb. K A1, K3 = 84 lb. K A .

Magnesium was applied in 1986 to wheat only as follows:

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, K3 = 84 lb. K A .

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

of 40 lb. Al at 1 inch soil depth on 11 June 1986 and 10 June 1987. In 1986









and 1987, 1 inch water A1' was applied preplant and at intervals during the

growing season when tensiometers placed at 6 inchessoil depth reached 0.02

MPa. Insecticides were not applied at any time during the experiment.

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 stages

(R6) in both years.

Insect sampling was carried out as described by Kogan and Pitre (1980) and

Todd and Herzog (1980). All plots were sampled on each sampling date by

beating the plants on both sides of the row into a 36 inch 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 VBC and SGSB.

The influence of fertilizer treatment on population densities and

population cycles of VBC larvae, SGSB nymphs, and SGSB adults were evaluated

by ANOVA. Data from each growing season were analyzed separately. The design

was a split plot over time (Steel and Torrie, 1960). The main effect of

fertilizer treatment compared the influence of fertilizer treatment on

seasonal population density. Orthogonal comparisons were used to define

fertility treatment differences. The interaction of date X treatment compared

the influence of fertilizer treatment 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. In 1986, mean yields were

significantly greater for the P2 P3, and P4 levels than the P, level, but









significantly similar for the P2 P3, and P4 levels. Mean yields in 1987 were

significantly greater at the P3 and P4 fertility levels than at the Pi and P,

levels, with yields significantly greater at the P2 level than at the P,

level. Yields were significantly greater both years for the K2 and K levels

than the K, level, with yields similar for the K2 and K, levels. In 1986,

yields were significantly greater for the Mg3 level than the Mg1 and Mg2

levels, with yields greater for the Mg2 than the Mg1 level. Yields were not

significantly affected by Mg fertility levels in 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). Population densities are described in terms

of daily and seasonal variation. Population cycles are recognized in figures

in relation to insect numbers/meter of row and stage, and date or plant

physiological stage.

Population densities of VBC were very low each year until soybean Growth

Stage R5; then, densities increased in all treatments and were greatest on the

last sample date in both years (Fig. 1). In both years, density estimates in

all treatments were greater than the economic threshold density (12 larvae per

39 inches (meter) of row [Johnson et al., 1988]) on sample dates during

soybean Growth Stage R6. Adult populations of SGSB invaded and began

reproducing during Growth Stage R4, but data for adults are not shown due to

poor precision of sample estimates resulting from a clumped dispersion pattern

typical of adult SGSB populations (Schumann and Todd, 1982). Population

densities of SGSB nymphs in 1986 were low in all treatments until soybean

Growth Stage R6, with density estimates exceeding the economic threshold

density (3 per 36 inches of row [Johnson et al., 1988]) during R6 (Fig. 2A).

Densities remained low on all sample dates in 1987, with estimates always









below the economic threshold density.

The population densities of larval VBC differed between fertility

treatments in 1986 (F=7.6; df=7,21; P<0.01) and 1987 (F=3.1; df=10,30;

P<0.01). Orthogonal comparisons were used to separate the effects of P, K,

and Mg levels on VBC population densities. Density estimates were

significantly affected by P levels. Population cycles of VBC for treatments

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

IA 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 Pi, P2, and P3 levels in 1986 (F=9.0; df=l,21; P<0.01), but

not in 1987. Mean densities also were significantly greater in treatments at

the P2 and P3 levels than in treatments at the P1 level in 1986 (F=26.0;

df=l,21; P<0.001) and 1987 (F=7.9; df=l,30; P<0.01).

Density estimates of VBC were significantly affected by K in 1987 (Fig.

2B), but not in 1986 (Fig. 2A). Population cycles of VBC for treatments at

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

1B. Treatments at the K2 levels were not sampled in 1986. Orthogonal

treatment comparisons were used to show that estimates in 1987 were

significantly greater in treatments at the K2 and K, levels than at the K

level (F=11.0; df=1,30; P<0.01), with estimates similar at the K2 and K3

levels. Orthogonal comparisons also revealed that VBC estimates were not

significantly affected by Mg 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=4.3; df=49,168; P<0.01) and 1987 (F=2.1; df=60,198; P<0.01),

because estimates were similar on sample dates when densities were low and not

similar for some treatments on dates when estimates were greater (Fig. 1A and









1B).


The density estimates of nymphal SGSB differed between fertility treat-

ments in 1986 when populations were very great (F=2.2; df=7,21; P=0.07), but

not in 1987 when populations remained very low (F=0.05; df=10,30; P=0.87).

Population cycles of nymphal SGSB at different levels of P, but constant

levels of K and Mg, are shown in Figure 2A. Orthogonal treatment comparisons

revealed that density estimates were affected by P levels. Mean densities

were significantly greater at the P and P4 levels than at the Pi and P2

levels (F=7.8; df=l,21; P<0.01), but were similar at the P3 and P4 levels.

Mean densities also were greater at the P2 than the Pi level (F=4.7; df=l,21;

P<0.01).

Orthogonal comparisons revealed that density estimates were not

significantly affected by K or Mg in 1986 and 1987 (data not shown). The

treatment x date interaction was not significant in 1987. This interaction

was significant in 1986 (F=2.5; df=49,168; P<0.01), because estimates were

similar on sample dates when densities were low and not similar for some

treatments on dates when estimates were greater (Fig. 2A).

Fertility levels of P, therefore, greatly affected population dynamics of

VBC and SGSB. For both pests in 1986, increased fertility levels of P that

did not result in a significant yield increase did result in significant

increases in pest population densities. Although yields were statistically

similar at the P2, P3, and P4 levels, population densities of VBC and nymphal

SGSB were significantly increased from P2 and P3 to P4. In 1987, soybean

yields were highest at and statistically similar for the P3 and P4 levels,

wjile VBC population densities were significantly highest at and statistically

similar for the P2, P3, and P4 levels. Fertility levels of K in 1986

significantly affected population densities of VBC. However, these effects









were the same as effects on soybean yield. Population densities of VBC in

1987 and SGSB nymphs 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 never

significantly influenced by Mg levels.

The reason why soil fertility levels affected population dynamics of these

major pests is unexplained. Soil fertility level may be directly affecting

pest populations through alterations in crop growth or nutritional level. Or,

the pest populations may be indirectly affected by effects of crop growth or

nutritional level on important natural enemies of the pests, such as bigeyed

bugs (Hemiptera:Lygaeidae), 'damsel bugs (Hemiptera: Nabidae), and spiders

(Aranaea: Araneidae). Our results showing effects of soil fertility on

population dynamics of the major pests 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. 1957. Influence of irrigation and fertilizer on populations

of three species of mirids attacking cotton. FAO Plant Prot. Bull.

6:33-36.

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.









Herzog, D.C. and J.E. Funderburk. 1986. Ecological bases for habitat manage-

ment and cultural control. In: M. Kogan (ed.) Ecological theory and

integrated pest management practice. Wiley interscience, N.Y. p. 217-250.

Johnson, F.A., J.E. Funderburk, D.C. Herzog, and R.K. Sprenkel. 1988.

Soybean insect control. Univ. of Fla, North Fla. Res. and Educ. Ctr.,

Quincy, FL, Ext. Entomol. Rep. #58:1-27.

Kogan, M., and H. N. Pitre, Jr. 1980. General sampling methods for above-

ground populations of soybean arthropods, pp. 30-60. In: M. Kogan and D.

C. Herzog (ed.) Sampling Methods in Soybean Entomology. Springer-Verlag,

Inc. New York.

McGarr, R.L. 1942. Relation'of fertilizers to the development of the cotton

aphid. J. Econ. Entomol. 35:482-483.

McGarr, R.L,. 1943. Relation of fertilizers to the development of the cotton

aphid in 1941 and 1942. J. Econ. Entomol. 36:640.

Musick, G.J. 1985. Management of arthropod pests in conservation-tillage

systems in the southeastern U.S. pp. 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.

Rhoads, F.M., and R.D. Barnett. 1990. Soybean yield and soil test

phosphorous, potassium, and magnesium. 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.

Schumann, F.W., and J.W. Todd. 1982. Population dynamics of the southern

green stink bug (Heteroptera: Pentatomidae) in relation to soybean

phenology. J. Econ. Entomol. 75:748-753.









Steel, R. G. D., and J. H. Torrie. 1960. Principles and procedures of

statistics with special reference to the biological sciencGraw-Hill, Inc.,

NY, 481 pp.

Todd, J.W., and D.C. Herzog. 1980. Sampling phytophagous pentatomidae in

soybean. In: M. Kogan and D.C. Herzog (ed.) Sampling Methods in Soybean

Entomology, Springer Verlag, Inc., New York. p.438-478.

Walker, J.K., G.A. Niles, J.R. Gannaway, D.R. Bradshaw, and R.E. Glodt. 1976.

Narrow row planting of cotton genotypes and boll weevil damage. J. Econ.

Entomol. 69:249-253.

Walker, J.K., J.R. Gannaway, and G.A. Niles. 1977. Age distrubition of cotton

bolls and damage from boll weevil. J. Econ. Entomol. 70:5-8.

ACKNOWLEDGEMENTS

Our thanks to E. Brown, Agricultural Technican IV; 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' test (Melich-I extractant) from fertility

plots in the soybean-fertility-pest experiment in 1986 and

1987 at Quincy FL.




Soil-test levels (ppm) across reps.


P, = 82



P, = 75


Table 2. Soybean yields (bu/A) in relation to fertility treatment and
year with no.pesticide treatment, Quincy FL.


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


P, = 25



P, = 17


Year

1986



1987


1986



1987
























70
1986 8

SKP ,Mg

KP, Mg,
40



20
310




180 189 203 217 228 238 252 285 275 281

DAY OF


V4 R1-2 R3 R4 R5 R6 R6
70
1987 A
so

so-


P. K.Mo.
20
SK,Ma




10









4o K,P. Mg

0 ----h 7 KP. Mg,
SK,P Mg,




1o

150 180 203 217 228 238 252 285 275 28s


Mean population density [number insects/39 inches (meter) of row] of larval
velvetbean caterpillars in relation to day of year (Days Julian, 1986, and
1987) and physiological stage of soybean development in treatments differing
in soil fertility levels (A) of P, but at the same level of K and Mg and (B)
of differing soil fertility levels of K but at the same level of P and Mg.


V3 V5-6 R1R2 R4 R5 R6 RS


1988 B K,P, Mg,

60

40 K.P.Mg,



20

10


180 18 203 217


V4 R1-2 13 R4 RS R6 R6
7r
1987 A
so

o60

40

30

20

10



70
1987 B
gol- --

5so


30



toF
20- ----------- -----
10---------------'--:--.--,---I-


226 230 252 265 275 225 180 189 203 217 220 236 252 268 275 285


DAY OF YEAR




Mean population density [number/39 inches (meter) of row] of nymphal southern
green stink bugs in relation to day of year (Days Julian, 1986, and 1987) and
physiological stage of soybean development in treatments differing in soil
fertility levels (A) of P, but at the same level of K and Mg and (B) of
differeing soil fertility levels of K, but at the same level of P and Mg.


Figure 1.


Figure 2.




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