Insecticide and tillage effects on pest and non-pest arthropods in corn agroecosystems

Agriculture, Ecosystems and Environment, 15 (1986) 11--21

11

Elsevier Science Publishers B.V., Amsterdam - - Printed in The Netherlands

INSECTICIDE A N D TILLAGE EFFECTS ON PEST A N D NON-PEST A R T H R O P O D S IN CORN AGROECOSYSTEMS

B.R. STINNER, H.R. KRUEGER and D.A. McCARTNEY

Department of Entomology, Ohio Agricultural Research and Development Center, The Ohio State University, Wooster, OH 44691 (U.S.A.) (Accepted for publication 1 August 1985)

ABSTRACT Stinner, B.R., Krueger, H.R. and McCartney, D.A., 1986. Insecticide and tillage effects on pest and non-pest arthropods in corn agroecosystems. Agric. Ecosystems Environ., 15: 11--21. Effects of carbamate and organophosphate insecticides, tillage and previous cropping history on pest and non-target soil arthropods in corn are reported. Also, degradation patterns o f organophosphate insecticide were quantified in plowed and no-tillage systems. Overall, tillage and cropping sequence had greater effects on arthropod communities than did insecticide treatments. Rootworm (Diabrotica sp.) damage was less in notillage than in plowed systems. There was no significant difference between insecticides in affecting rootworm damage. The organophosphate-treated corn had less black cutworm (Agrostis ipsiion) damage than did the carbamate-treated corn. Cryptostigmata mite density was highest in no-tillage systems. In contrast, non-cryptostigmata mite density was highest in fallow--plowed systems. The carbamate insecticide had a greater negative effect on overall mite density than did the organophosphate compound. With respect to soil macroarthropods, herbivore numbers were highest in plowed systems and lowest in no-tillage systems. Spider numbers were highest in the no-tillage systems. The organophosphate insecticide degraded more rapidly in the no-tillage compared to the plowed systems; however, this difference did not appear to affect arthropod numbers.

INTRODUCTION

This paper compares the relative effects 0f soil-applied insecticides and tillage on pest and non-pest arthropod communities. Attention is also given to differences and similarities in arthropod communities associated with corn after fallow treatment vs. those associated with continuous corn cropping. In this study, we are concerned primarily with soil-inhabiting arthropods. Application of soil insecticide for control of rootworm (Diabrotica sp.) represents the major use of insecticides in corn production. Carbarnates and organophosphates are the t w o major classes of insecticides used for soil application in corn systems. These insecticides are usually applied

0167o8809/86/$03.50

© 1986 Elsevier Science Publishers B.V.

12 in granular form and can be toxic to other corn pests such as black cutworms (Agrotis ipsilon) and wireworms (Dicke, 1977; Gray et al., 1984). Tillage and crop rotation can significantly alter the activities of both pest and non-pest arthropods (House and Stinner, 1983; Blumberg and Crossley, 1983). These non-pest arthropods include taxa involved in both entomophagous and residue decomposition processes. Since non-target arthropods presumably can be affected by soil insecticides, we thought it important to consider both effects of tillage and insecticides on nontarget as well as target (pest) species. Continuous vs. fallow rotation should also have significant effects on both pest and non-pest arthropod species, caused by changing host plant resources and affecting soil residues. In this paper, we present data on the effects of tillage rotation and soil insecticides (cloethocarb, a carbamate and terbufos, an organophosphate) on: (1) rootworm and cutworm damage (major pests in the U.S. corn belt), (2) soil microarthropod communities and (3) soil macroarthropod communities. In addition, since tillage is thought to affect insecticide persistence, data on degradation patterns of terbufos are shown and kiiscussed. MATERIALS AND METHODS

Our experiment was carried out on land situated on the Ohio Agricultural Research and Development Center, Wayne County, Ohio. Soil type is a clay loam of the Wooster series. The area receives an average of 95 cm precipitation per year. Daily mean temperatures range from -3°C in January to 21°C in July. One field (0.8 ha) was cropped in continuous corn under conventionally moldboard-plowed (spring) management. Another field (1.1 ha) was managed with no-tillage methods in continuous corn and a third contiguous area (0.7 ha) was fallowed 1 year (1981) prior to our study.

Farming practices and treatments On 12 May 1982, both plowed continuous corn and the fallow area were moldboard plowed and disked. The no-tillage system received no seedbed preparation. Pioneer 3780 seed corn was planted in all three systems in 75-cm wide rows. The soil insecticides were applied as granules with a Gandy box on 13 May 1982. The insecticides were applied on the soil surface in an 18-cm wide band over the corn rows at a rate of 0.11 g active ingredient per meter of row. Bladex (2.2 kg ha-l), Lasso (2.2 kg ha -1) and Paraquat (1 1 ha -~) herbicides were used for weed suppression. Fertilizer was applied at the rate of 100 kg ha -~ N, 60 kg ha -~ P and 60 kg ha -1 K. These preparations resulted in the following cropping systems: (1) plowed corn following corn, (2) plowed corn following fallow and (3) no-tillage corn following corn. The insecticide treatments (carbamate, organophosphate and no insecticide) were randomly applied (4 replicate blocks each) within each of these cropping systems.

13

Sampling and analyses Rootwo.rm damage ratings were obtained by digging, washing and evaluating corn root systems utilizing the Iowa 1--6 scale (Hill and Peters, 1971). Black cutworm damage was evaluated by counting the number of damaged corn plants per unit row length. Microarthropods (mites, collembola, beetle larvae) were sampled from 3.6-cm diameter × 5~cm deep soil cores, n = 12 per treatment. Samples were collected on 4 dates during the growing season. The arthropods were extracted with a modified Tullgren apparatus (Merchant and Crossley, 1970). The animals were sorted to the following groups: collembola, cryptostigrnata mites and non-cryptostigmata mites (predominantly mesostigmata). Macroarthropods (spiders, carabid beetles, etc.) were sampled (relative density) with pitfall traps constructed from 1-1 plastic cups containing 50 ml of ethylene glycol. The traps were opened for 24 h every 3 weeks. Twelve traps were run during each collection period in each treatment. Samples were placed in 70% EtOH and sorted to at least family level. Terbufos and its oxidation products were analyzed from 2.5¢m diameter × 15-cm deep soil cores. Four samples were collected from each treatment on 20 May, 7 June and 15 July; each sample was comprised of three soil cores, taken within 5 cm of the corn rows. Soil samples for insecticide analysis were collected from the no-tillage and continuously cropped plowed systems only. Gas chromatographic (GC) analyses were performed using a Perkin-Elmer model 3920B chromatograph equipped with a H2 flame ionization detector. The GC column was a 1.0 m × 4 mm ID glass coil, packed with 10% DC200 on 100--120 mesh "Gas42hrom Q" and operated at 175°C. The flow rate of nitrogen carrier gas was 100 ml min -I. Inlet and interface temperatures were 220 and 230°C, respectively. A well-mixed 50 g sample was blended for 5 min in 100 ml of a mixture of methanol and acetone (1:1) and filtered through glass filter paper contalning anhydrous sodium sulfate. The filtrate was evaporated to dryness and the residue re
Pest density and damage to corn In carbamate and organophosphate treatments, as expected, rootworm damage was reduced in continuous corn situations (Table I). Rootworm damage was lower in plowed--fallow than in no-tillage, which was lower than in conventional plowed (non-fallow) systems. Other studies also have

14 TABLE I Pest d a t a f o r c o r n . R o o t ratings, n = 16, BCW damage, n = 8. OP = o r g a n o p h o s p h a t e , CAB = c a r b a m a t e , CON = c o n t r o l . R o o t ratings are b a s e d o n t h e Iowa 1---6 scale. Black c u t w o r m d a m a g e r e p r e s e n t e d as n u m b e r o f c u t p l a n t s p e r m e t e r o f row. Values foll o w e d b y t h e s a m e l e t t e r are n o t significantly d i f f e r e n t at t h e 0.05 level b a s e d o n Chis q u a r e n o n - p a r a m e t r i c statistics for t h e r o o t w o r m d a m a g e a n d D u n c a n ' s m u l t i p l e - r a n g e test for the cutworm data Plowed fo~owing fallow

P l o w e d foUowing corn

No-tillage following c o r n

OP

CAB

CON

OP

CAB

CON

OP

CAB

CON

Root rating for r o o t w o r m damage

1.0a

1.0a

1.0a

2.0a

2.0a

3.4b

1.Sa

1.6a

2.0a

Black c u t w o r m damage

0.17a

0.27a

0.25a

0.02a

0.02a

0.03a

0.10a

0.14a

0.15a

indicated lower rootworm damage in no-till compared to plowed systems (Musick and Collins, 1971; Chiang, 1973). Reasons for this pattern are not entirely clear; both differences in adult oviposition behavior and overwintering mortality have been noted (Stinner, unpublished data). Table I shows that organophosphate-treated areas had less black cutworm damage relative to paired untreated plots than did the carbamate compound in both continuous corn systems. However, we point out that black cutworm damage levels did not exceed Ohio State University's economic threshold of 5% cut plants.

Soil microarthropods The microarthropod numbers were dominated by cryptostigmatid (primarily oribatid) mites (Fig. 1), as is typical for many agricultural as well as non-agricultural softs (Anderson, 1975; Stinner and Crossley, 1980). These mites, along with coUembola, are important components in plantresidue decomposition processes. The animals help break down the residue particles, increasing surface area, which promotes bacterial and fungal growth and ultimately results in release of inorganic nutrients (Dindal, 1973). Cryptostigmata mite density showed no dramatic differences among tillage and fallows vs. continuous corn treatments. However, during late summer, numbers tended to be somewhat higher in plowed-fallow than in either continuous no-tillage or fallow--rotation plowed systems (Fig. 1). Others have reported that plowing tends to lower mite numbers, presumably through either mechanical disturbance or burying plant residues (Ghilarov, 1973; Stinner and Crossley, 1980). Non-cryptostigmatid (primarily meso-

15

INSECTICIDE

TILLAGE EFFECTS

EFFECTS

coLLEMBOI'A

COLLEMBOLA a

,,,'.,,,

,,',,

/*/

1

/ /

---..... i

~J

i

h

NON-CRYPTOSTIGMATA

MITES

i

NON-CRYPTOSTIGMATA

MITES

0f

I

1 i

j/

,~

/// ,:'i/

'~1

CRYPTOSTIGMATA

MITES

j

I

I

CRYPTOSTIGMATA

I

MITES

J

,"..

!

/ /'

z

,.

J

/i i

MAY

i

JUNE

i

JULY

i

AUG

ill

SEPT

MAY

JUNE

JULY

AUG

SEPT

Fig. 1. M i c r o a r t h r o p o d d e n s i t y in 10 ~ per m: for c o l l e m b o l a and n o n - c r y p t o s t i g m a t a m i t e s and in 103 per m ~ for c r y p t o s t i g m a t a mites. N u m b e r s on the h o r i z o n t a l axes are dates for 1 9 8 2 . The left hand c o l u m n o f figures represent tillage e f f e c t s (plowed-fall o w .... p l o w e d - - c o n t i n u o u s corn---, n o - t i l l a g e - - c o n t i n u o u s corn . The right hand c o l u m n s h o w s i n s e c t i c i d e e f f e c t s ( n o insecticide , carbamate---, o r g a n o p h o s p h a t e . . . ) . Bars indicate p o o l e d standard errors.

16

stigmatid) mites were relatively numerous in our soil samples (Fig. 1). Their density was appreciably higher in the no-tillage system. Fallow-rotation versus continuous corn--plowed systems had a smaller impact on these animals. These mites have been reported to prey on rootworm eggs (Chiang, 1978). The collembola data indicated no distinct trends among the tillage and fallow treatments, but appreciably higher numbers in July in plowed--continuous corn systems were observed (Fig. 1). The effects of the insecticides on the soil microarthropods, 8s with the cropping systems, varied with taxa. Collembola and cryptostigmata mite density increased appreciably following treatment with carbamate insecticide. Non-cryptostigmata mite density exhibited no observable response to insecticide treatment (Fig. 1). Various studies have documented effects of soil insecticides on microarthropod communities. Most of the reported findings also have found effects of insecticides varying with different taxonomic groups (Edwards and Thompson, 1973). What does appear important in our study is that tillage and rotation patterns had more marked influence on microarthropods than did insecticides.

Soil macroarthropods Table II lists the macroarthropod taxa included in the different trophic groups. Relative density of total macroarthropods was highest in the fallow system prior to plowing and planting (Fig. 2). Although total numbers of macroarthropods fluctuated throughout the growing season, significant differences among the three cropping systems were observed. Herbivore numbers peaked in early June when damage to young plants can be very severe. The plowed--continuous corn system had the highest herbivore density and no-tillage the lowest. The plowed~ontinuous corn system also had highest numbers of herbivore macroarthropods throughout much of the remaining season. Detritivore numbers in the fallow and continuous corn--plowed systems were greatest prior to plowing, probably largely attributable to the accumulation of plant residues. Prior to planting, the fallow system had higher numbers of predators than did the other two cropping systems. Later in the growing season, there were less distinct TABLE

II

Taxa included in each macroarthropod trophic group Carabids -- Carabidae Spiders -- Arachnida Total predators -- Arachnida, Carabidae, Staphylinidae, Formicidae, Chilopoda, Coccinellidae Herbivores--Gryllidae, Diabrotiea, Mollusca, Curculionidae, Gryllinae, Hemiptera Detritivores --Nitidulidae, Diplopoda, Isopoda

17 differences among the three cropping systems in carabid and total predator numbers (Fig. 2); but, at least through the mid,summer months, spider numbers were highest in the no-tillage--continuous corn system. Compared to the three different cropping treatments, insecticides had relatively small effects on the macroarthropods (Fig. 2). One interesting exception is that both insecticide treatments had higher herbivore numbers than the untreated areas during June. This finding is difficult to attribute to lower predator numbers, since the predators appeared to be unaffected by insecticide applications. Yet, we should add the caveat that some of these predators, especially the larger carabids, will move over fairly large distances, which would tend to mask the influence of insecticides. Others have reported varying effects of tillage on both pest and beneficial species of soil macroarthropods. Studies by Musick (1972) and Gregory and Musick (1976) concluded that the mulch layer in reduced tillage systems provided a favorable habitat for some pest and beneficial arthropods in corn systems. House and All (1981) reported carabid beetle numbers and species diversity several times higher in no-tillage than in conventionally tilled soybeans. More recently, Blumberg and Crossley (1983) found that species diversity of soil macroarthropods was greater in no-tillage than either plowed or fallow systems. As with the data from the present study, they reported that spider and carabid predatory guilds were significantly affected by tillage.

Terbufos (organophosphate) degradation The relative rate of terbufos degradation (Fig. 3), as influenced by conventional and no-tillage treatments, indicates that a significantly higher loss of terbufos occurred in the no-tillage treatment after only 7 days following application. We point out that the data say nothing about the mechanisms involved in degradation -- physical, biological and so forth, only the concentrations remaining after certain lengths of time. The levels of terbufos and sulfone residues were almost twice as high in the no-tillage treatment on 7 June and both treatments dropped to < 0.3 p.p.m, by 15 July. The reason for the shift in relative levels between treatments on 7 June is not known. The levels of terbufos sulfone decreased from a high of 0.1-- 0.3 p.p.m, at the 20 May collection to < 0.01 p.p.m, for the next two collections. There was no obvious relationship between degradation patterns and effects of soil arthropod communities. In conclusion, tillage and rotation had more marked effects on arthropod communities than did organophosphate or carbamate insecticides. Difference in degradation patterns of the organophosphate insecticide between tillage treatments appeared to have no observable influence on arthropod numbers.

18

TILLAGE EFFECTS

INSECTICIDE EFFECTS DETRITIVORES

DETRITIVORES 4n

I

i

i

"

--I

.......

~ ........

r .......

r

OI

HERBIVORES

i

h

i

i

i

i

i

i

HERBIVORES

/',

,,'\

TOTAL

MACROARTHROPODS

TOTAL

I

MACROARTHROPODS

f.-f

',

I

. . . . ,

L

,/

01

MAY

JUNE

JULY

AUG SEPT

OCT

i

MAY

JUNE

k

h

JULY

i

i

AUG SEPT

i

OCT

19

INSECTICIDE EFFECTS

TILLAGE EFFECTS SPIDERS

SPIDERS 6!

"r i/, ¸¸ -

'/ / '" /

, ""'"/

if

/

""

oI

i

TOTAL

,

i

.

~.

CARABIDS

:ARABIDS

i

T

i

a

i

h

h

i

PREDATORS

TOTAL

PREDATORS

lOl-

'!

!

21-

!

x./ ol

MAY JUNE JULY

AUG SEPT

OCT

,

MAY

k

JUNE JULY

,

AUG S E P T

i

i

OCT

Fig. 2. Macroarthropod density in mean (n = 36) numbers per pitfall trap. Numbers on the horizontal axes correspond to Julian dates for 1982. The left hand columns of figures represent tillage effects (plowed--fallow .... plowed--continuous corn---, notillage---continuons c o r n ~ ) . The right hand columns show insecticide effects (no ins e c t i c i d e ~ , carbamate---, organophosphate...). Bars indicate pooled standard errors.

20 3.0 ~ Application

o

~.0~

=

\ \

o

\

g

\

•.~

o..

\

I

1.0

No-tilloge \

\ rQ

MAY 1,4

MAY ZO

JUNE 7

"

\

JULY 15

Fig. 3. Terbufos degradation patterns in plowed and no-tillage soils. Bars indicate standard errors. Numbers on the horizontal axis correspond to data for 1982.

ACKNOWLEDGEMENTS

The authors thank James Mason, Ann Nobles and Darryl Woods for their assistancein this project.

REFERENCES Anderson, J.M., 1975. Succession, diversity and trophic relationships of some soil animals in decomposing leaf litter. J. Anita. Ecol., 44: 475--495. Blumberg, A.Y. and Crossley, D.A., Jr., 1983. Comparison o f soil surface arthropod populations in conventional tillage, no-tillage and old field systems. Agro-Ecosystems, 8: 247--253. Chiang, H.C., 1973. Bionomics of the northern and western corn rootworms. Annu. Rev. Entomol., 18: 47--72. Chiang, H.C., 1978. Pest management in corn. Annu. Rev. Entomol., 23: 101--123. Dicke, F.F., 1977. The most important corn insects. In: G.F. Sprague (Editor), Corn and Corn Improvement. Agronomy 18. Am. Soc. Agron., Madison, WI, pp. 501--589. Dindal, D.L., 1973. Symbiotic relationships of soil invertebrates. In: Dindal, D. (Editor), Soil Microcommunities. I. USAEC, Off. Inf. Technol. CONF-711076. USDC, Springfield, VA. Edwards, C.A. and Thompson, A.R., 1973. Pesticides and the soil fauna. Residue Rev., 45: 1--79. Ghilarov, M.S., 1973. General trends of changes in soil animal populations of arable land. In: Jan Vanek (Editor), Progress in Soil Zoology. Academia, Czechoslovakia, pp. 31--39.

2] Gray, M.E., Coats, J.R. and Tonefson, J.J., 1984. Effect of an insecticide and herbicide combination on corn r o o t w o r m damage (Coleoptera: Chrysomelidae). J. Econ. Entomol., 77 : 4~.5--467. Gregory, W.W. and Musick, G.J., 1976. Insect management in reduced tillage systems. Bull. Entomol. Soc. Am., 22: 302--304. Hill, T.M. and Peters, D.C., 1971. A method of evaluating postplanting insecticide treatments for control of western corn r o o t w o r m larvae. J. Econ. Entomol., 64: 764--765. House, G.J. and All, J.N., 1981. Carabid beetles in soybean agroecosystems. Environ. Entomol., 10: 194--196. House, G.J. and Stinner, B.R., 1983. Arthropods in no-tillage soybean agroecosystems: c o m m u n i t y composition and ecosystem interactions. Environ. Manage., 6: 23--28. Merchant, V.A. and Crossley, D.A., Jr., 1970. An inexpensive, high-efficiency Tullgren extractor for soil microarthropods. J. Ga. Entomol. Soc., 5 : 84--87. Musick, G.J. and Collins, D.L., 1971. Northern corn r o o t w o r m affected by tillage. Ohio Rep., 1971: 88--91. Musick, G.J., 1972. Control of armyworm in no-tillage corn. Ohio Rep., 58: 42--45. Stinner, B.R. and Crossley, D.A., Jr., 1980. Nutrient cycling in till and no-till systems. An experimental approach to agroecosystem analysis. In: D. Dindal (Editor), Soil Biology as Related to Land Use. EPA, Washington, DC, pp. 280--288.