IMlMlStalM 0(^MHllMntOf A#lcultur« Ecological Impact Agicultural R^earch Service Of Parathlon Technical BulMin NufTitoer1Ô6& In Soybeans
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■-0 Vegetative Fauna (Part I)
Abstract Marston, N. L, and Hennessey, M. K. 1982. Ecological Impact of Parathion in Soybeans.—Vegetative Fauna. U.S. Department of Agriculture, Technical Bulletin 1665.28 p. An application of ethyl parathion to flowering soybeans reduced populations of predatory arthropods by 66 percent 6 days posttreatment. Egg and lan/al parasites of the green cloverworm, Plathypena scabra (F.), the most abundant caterpillar species, also were reduced. The green cloven/vorm population decreased by 83 percent 6 days after the applica- tion. Populations of secondary pests and detritus feeders similarly were affected. Most species made a remarkable comeback and reached checkf ield levels or higher 4 weeks after treatment. The population of green cloven/vorms increased to a maximum level 2.3 times higher than in the check field during pod fill, apparently caused by decreased prédation and parasitism of eggs and early instars. Survival of the resurgent population was low, however, and few 6th instars were noted in either the treated or check fields. Percent defoliation and yield did not differ in the two fields. KEYWORDS: soybeans, arthropods, insecticides, biological control, ecology, parathion.
Acknowledgments We want to express our thanks to D. A. Current, G. E. Boutz, and Barbara Campbell for their help in conducting the experiment and counting the insects. We also thank J. S. Williamson for the use of his fields.
(See also abstract and acknowledgments for Soil Arthropod Fauna on page 8.) Although the research for this publication was completed ¡n the midseventies, the results are as appropriate today as when the tests were conducted. No other studies have been conducted and published that duplicate the results published here.
This publicaltion reports research involving pesticides, it does not contain recommendations for their use nor does it impiy that the uses discussed here have been registered. Ali uses of pesticides must be registered by appropriate State and/or Federal agencies before they can be recommended.
í/4ep44áanimals, beneficial insects, desirable plants, and fish or other wildlife—if they are not handled or applied properly. Use all pesticides selectively and carefully. Follow recommended practices for the disposal of surplus pesticides and pesticide containers.
Trade names and the names of commercial companies are used in this publication solely to provide specific information. Mention of a trade name or manufacturer does not constitute a guarantee of warranty of the product by the U.S. Department of Agriculture or an endorsement by the Department over other pro- ducts not mentioned.
Ill Contents
Vegetative Fauna (Part I) 1 Introduction 1 Matehals and methods 1 Results 3 Discussion , 6 Literature cited 7
Soil Arthropod Fauna (Part II) 9 introduction 9 Study area 9 Sampling methods 9 Taxonomic list of soil arthropods collected 11 Results 13 Soil-core sampling 13 Pitfall-trapping study 17 Discussion 21 Literature cited 22 Appendix 1 23 Appendix 2 23
Issued Decembe Vegetative Fauna (Part I) Norman L Marston and Michael K. Hennessey^
Introduction flowering (R2) on August 2. We used 0.18 We took an overall sample of 15.25 Several studies demonstrate that kg Al in 7.6 L water per 0.4 ha as row-m so that we could measure ac- applications of pesticides to soybeans specified for foliar insect control in the curately the low populations, especially can have detrimental effects that may Missouri "Insect Control Recommenda- those just after treatment. The D-Vac outweigh their immediate benefit. tions" (2). The control field received no loses efficiency, however, as the bag Predators have been shown to be killed insecticide. fills with debris, and we found that such readily (4,10,22)? and chemicals disrupt Sampling Sites.—Three sampling a long sample underestimates popula- the natural epizootics of fungus sites were located in the treated field in tions. We divided each overall sample, diseases of pest species (7,9). This such a way that we could measure therefore, into 3.05-m and 12.20-m sec- often leads to resurgence of gradual recolonization of the field after tions to adjust the data for this reduced lepidopteran lan/ae to a level greater we decimated the arthropods with the efficiency and then multiplied each than that in untreated fields (15). insecticide (fig. 1). The outer plot was 12.20-m sample by a constant (C) Insecticides also may disrupt the about 60 m from the margin nearest to derived as follows: soil ecosystem. Tests show that the control field, the middle plot was 3.05 row-m sample x 4 populations of surface-active predators midway between the margin and the • ~ 12.20-m sample may be reduced (13,14), and those center of the field, and the inner plot This constant did not vary organisms responsible for the break- was at the center. One sampling site significantly among the arthropod down of organic debris may be affected was located in the control field, about groups counted (P>0.05), but it did vary aswellf72j. 120 m from the margin nearest the from week to week. (C varied from 1.35 Our objective in this study was to treated field and on a line running to 2.63, reflecting a loss of efficiency on monitor the effects of a parathion ap- through the sites in the treated field. the longer segment of 26 to 62 pet.) Data plication on arthropods. We studied all in the tables and graphs are means of aspects—plant, soil surface, and sub- D-Vac Samples—Our basic sampl- two 15.25 row-m samples (each from soil—with emphasis on the beneficial ing tool was the D-Vac.® We used an at- combined 3.05-m and adjusted 12.20-m organisms. We are reporting here the ef- tached cone (No. 304) with a distal subsamples). fect of the insecticide on arthropods on diameter of 20 cm to increase the suc- We took a pretreatment sample 3 the plants. tion at the opening (fig. 2). The cone was days before treatment. The first post- maneuvered from the bases of the treatment sample was taken 4 days Materials and Methods plants upward, then outward and down after the application in the check field We conducted our experiment in to the bases of the plants again in a cir- but was delayed by rain until 6 days 1974 in two fields, about 8 ha each, adja- cular motion as the sampler walked posttreatment in the treated field. We cent to the Missouri River 20 km slowly down each side of the row. This sampled weekly thereafter (except dur- southwest of Columbia, Mo. The soil, method insured that all foliage was ing the week of September 1 to 7 (mid- generally, is a fine sandy loam (Sarpy) sampled. R5), when we concentrated on plant- with about 2 percent organic content. We plowed, disked, harrowed, and treated the fields with a preemergence herbicide composed of 1.67 L alachlor Soybean [2-chlor-2',6'-diethyl-/V-(methoxymethyl) Check— acetanilide] and 0.45 kg linuron : Field IZZ [3-(3,4-dichlorophenyl)-1-methoxy-1- methylurea] per 0.4 ha. The fields were Uncultivated - planted to soybeans (var. 'Clark-63') on Areas ~"^^^ June 17 and 18 in 91-cm rows. Plant den- sity averaged 50 plants per 3.05 row-m at growth stage V7^ (3). The fields were cultivated twice. ! I ! I We treated one field by airplane Insecticide •Wheat- Treated Soybean with ethyl parathion [0, ikJiethyl • Field • : a ^Maratón is a research entomologist, Inner Biological Control of Insects Research Unit, Agricultural Research Service, U.S. Depart- ment of Agriculture, P.O. Box A, Columbia, Mo. 65205; and Hennessey is a graduate student, Department of Entomology, P.O. Box 5215, North Carolina State University, Raleigh, N.C. 27650. ^Italicized numbers in parentheses refer FIGURE 1.—Location of sampling sites In the parathion-treated and untreated to Literature Cited, p. 7. fields, McBaine, Boone County, Mo., 1974. and any native green cloverworms on the plants on semisynthetic diet to measure incidence of parasitism and disease. Instars of the green cioverworm larvae were determined by measuring the width of their head capsules. We conducted the tests the week before we applied the insecticide and weekly for 4 weeks afterward. There were seven replications at the center of the treated field and seven in the control field. Differences between the fields on each date were analyzed by x^ tests. Plant-Shake Samples.—By mid- pod fill (Septemt)er 1 to 7), we found a resurgence of lepidopteran larvae in the treated field. We discontinued the prédation tests, consequently, and con- centrated on collecting green clover- worms to measure more accurately their populations and obtain enough live lar- BN 49356 vae to measure accurately their rate of FIGURE 2. — D-Vac machine for sampling soybean arthropods. parasitism and incidence of disease. We used a 3.05-m x 0.8-m plastic sheet stapled to wooden slats as a substrate. We slid the sheet under the shake and sweep-net sampling). Dif- plants in the row and confined within a foliage without disturbing the plants ferences between the means for each barrier designed to inhibit emigration of and unfolded it to cover the entire space site on each sampling date were tested the larvae (fig. 3). We then placed 201st tietween the rows. The plants in one row by ANOVA and Duncan's Multiple Instars and 10 4th instars on the plants. then were bent over the sheet with a Range Test (P = 0.05). The counts were After 24 h, the plants were cut, placed In 1.72-cm diameter, 3.05-m-long aluminum transformed to Vx+Tto stabilize the plastic bags, and returned to the pipe and shaken vigorously to dislodge variance. laboratory, where the survivors were the larvae. The sides of the plastic sheet Prédation, Parasitism, and Disease counted. Some larvae may have then were joined, forming a tube, and of Lepidopteran Larvae.—We measured escaped, but this would have had little one end was lifted into the air, allowing prédation of caterpillars by recording effect on relative differences between the lan/ae to slide down into a bag. The survival of introduced, laboratory-reared fields and from week to week. Native larvae were returned to the laboratory, cabbage loopers, Trichoplusia ni loopers (Piusiinae) were not a source of counted, and reared on semisynthetic (Hübner). First, a group of atx)ut five confusion because they were rare. diet to measure parasitism and disease. plants was isolated from adjacent We reared the sun/iving loopers We took two samples at each of our four sampling sites on Septemtjer 3 (mid-R5). On September 9 (late R5), we took two samples at each site in the treated field, but eight samples were re- quired in the control field to obtain '^^ki'¿*'<''''5 enough larvae to measure accurately the percentages of parasitism and disease. On September 16 (R6), we took three samples at each site in the treated field and six samples in the control field. Percentage Defoliation and Yield.« —We measured the percentage defolia- lb tion in each field at R6 (September 20). Each field was divided Into quadrants, and 12 plants were selected on a diagonal line through each quadrant. Bfe^^.?.' The remaining surface area of the leaves was measured on a Li-Cor^ Model Li 3000 portable area meter (Lam- ba Instruments Corp.). The leaves were then photocopied, and their images (in- cluding the defoliated area) were cut out t and run through the machine again. The • differences between the surface area of V '^^^:Tf the leaves and their images estimated the area defoliated. We measured yield BN 49356 FIGURE 3.—Introducing cabbage looper lan/ae to measure prédation, in each field by taking eight 3.05 row-m parasitism, and disease. samples in each quadrant. Predators decrease suggests that emerging adults /3.05 Row-M migrated from the fields (10). 220- The nabid nymphal population was reduced by 72 percent the first week and 68 percent the second week after treat- 200 ment. Differences on the next four sampling dates were nonsignificant, but 180H Check the same pattern occurred each week. When the four dates were analyzed as a whole, the overall 43-percent reduction 160 was highly significant (P<0.005). Thus, the initial reduction in number of adults, combined with the apparent emigration 140H Insecticide Treatment of newly emerged adults from the field, resulted in a reduced population of nym- 120- phs for the rest of the season. Spiders were affected less by the application than the hemipteran 100- predators (table 1). They were reduced by only 57 percent relative to the check- field population. They then increased to 80 a level not significantly different from the check the following week. These 60- spiders were predominantly early in- stars, mostly Oxyopes salticus Hentz. Many of them may have entered the 40 field by ballooning since adults of 0. salticus are rare in soybeans in 20 midseason. We collected a variety of other predatory species, mostly adults and 1 T 1—I 1 \ 1 immatures of Scymnus sp. (Coc- 27 2 6 8 12 21 25 9 12 20 cinellidae), Geocoris spp. (Lygaeidae), July August September and Ctirysopa spp. (Chrysopidae). The decrease on August 8 was not signifi- FIGURE 4.—Seasonal trend of populations of predatory arthropods in cant, but on August 12 the population in parathion-treated and untreated soybeans. the treated field was only 56 percent of that in the check (table 1). Parasitic Arthropods.—The insec- Results prenjator groups, from the outer- to the ticide application affected the D-Vac Predatory Arthropods.—The insec- inner- sampling sites in the treated field, ticide application had a great effect on but the differences were small and collections of parasitic arthropods even the population of predators. Overall obscured by the variability. Recoloniza- more than it did the predators (table 1). numbers in the treated field (mean of the tion was so rapid that distance from the Trictiogramma were reduced by 99 per- three sampling sites) were reduced by field margin was of little significance. cent 6 days following the application. Remarkably, these tiny insects were col- 66 percent 6 days after treatment and by Orius nymphs were decimated to 51 percent 10 days after treatment (fig. lected in the center of the treated field an even greater extent than the adults on August 12 (10 days posttreatment) 4). By 19 days posttreatment, however, (table 1). Their population also took the population had rebounded to a level though their numbers were still only 31 longer to recover, probably because of percent of the population in the check of that found in the control field, and the lag between immigration of the these numbers were similar for the rest field. Differences between the two adults and production of new nymphs. fields, thereafter, were nonsignificant, of the season. We noted reductions of 79,89, and 67 Adults of Orius insidiosus (Say), partly caused by a decrease in the pei^cent during the 3 weeks following check-field population. Some the most abundant species, typified this treatment. These reductions may have trend. Their numbers were reduced by 67 Trictiogramma may have survived the in- been a critical factor allowing the subse- secticide as parasitized eggs since percent relative to the check-field quent resurgence of lepidopteran larvae population 6 days posttreatment (table parathion has been shown to have no since Orius nymphs are a major source ovicidal activity (1). 1), but they rebounded quickly and were of egg mortality iS;. as abundant as in the check field by We combined the three dominant August 21 (19 days posttreatment). This The effect of the parathion treat- larval parasites of the green clovenA/orm, rebound required a remarkably rapid in- ment on Nabidae (Nabis spp.) was Apanteles margim'ventris (Cresson), terchange of populations between fields similar to the effect on Orius (table 1). Rogas noloptianae Ashmead, and Pro- because the small number of nymphs Adults were reduced by 95 percent 6 tomicroplitis facetosa Weed, to remaining after treatment could not days posttreatment. Some recoloniza- measure the effect of the insecticide on have accounted for the rapid increase in tion was evident the following week, but braconids. None were collected the population of adults. the numbers then decreased in both week after spraying (Aug. 8), but they We noted some decrease in the fields, despite the considerable popula- were present in the August 12 collection number of Orius adults, as well as other tion of developing nymphs. This (table 1). Very few 3d- to 5th-instar green TABLE 1.—Arthropods per 3.05 row-m in parathion-treated and untreated ferences were noted between sampling soybeans, Columbia, IVIo., 1974^ sites (table 1). The week following the application, however, the population in Check Check the check field increased about Date and Area within field Date and Area within field treated field treated field threefold while the Insecticide reduced growth (un- growth (un- numbers in the treated field. This stage^ Inner Middle Outer treated) stage^ Inner Middle Outer treated) resulted in a population reduction of 83 Predatory arthropods percent relative to the check (fig. 5). The Orius insidiosus (ad u Its) Orius insidiosus (nymphs) August 12 sample, 10 days after applica- July30(R1).. . 31.8a 42.4a 75.5a 65.9a 11.6a 17.7a 19.0a 11.4a tion, showed a doubling of the popula- Aug.6-8(R2) . . 9.4a 11.4a 14.2a 35.7 b 5.0a 5.3a 8.1a 28.8 b Aug.12(R3) . . 55.0a 61.2a 77.8a 79.5a 5.5a 12.0a 7.7a 73.7 b tion In both fields, but there was still an Aug.21(R4) . . 57.2a 59.7a 78.8a 51.0a 15.0a 23.4a 26.7a 66.1 b 82-percent reduction from the check. Aug.26(R5) . . 17.5a 18.6a 24.4a 11.4a 33.5a 72.5a 77.5a 66.0a The 83-percent reduction on Sept.9(R5) .. . 6.1a 4.4a 5.3a 15.2 b 46.0a 66.5 b 71.9 b 46.8a August 8 (6 days posttreatment) may Sept.19(R6) . . 8.1a 7.8a 9.2a 5.9a 47.2a 36.6a 33.8a 28.0a have underestimated the initial effect of Nabidae (adults) Nabidae (nymphs) the Insecticide on larvae since those July30(R1).. . 5.5a 11.0a 12.6a 5.8a 2.3a 1.2a 6.4a 2.1a collected were 96 percent 1st instars, Aug.6-8(R2) . . .la .Oa .3a 1.9 b 5.6a 2.2a 2.5a 12.2 b which would have had to hatch after the Aug.12(R3) . . .7a 1.7a 1.9a 3.7a 6.2a 18.6a 13.6a 39.6 b Aug.21(R4) . . 1.0a .4a .4a .5a 5.3a 15.2a 14.8a 19.6a treatment. Larvae present on the Aug.26(R5) . . 1.4a .7a .3a .9a 7.4a 13.2a 14.3a 21.7a pretreatment sampling date (July 30) Sept.9(R6) .. . 1.1a .9a .5a .4a 9.4a 9.4a 7.5a 16.1a would have been at least 3d instars by Sept.19(R6) . . 1.2a .4a 2.0a 1.7a 9.2a 8.9a 7.7a 14.4a August 8, and no 3d to 6th instars were Spiders Other predators collected. July30(R1).. . 14.4a 12.8a 21.0a 28.6a 2.2a 4.3a 11.3a 3.5a The presence of 1st instars 6 days Aug.6-8(R2) . . 15.5a 17.8a 16.4a 38.3 b 6.4a 4.4a 2.3a 8.8a posttreatment emphasizes a major Aug.12(R3) . . 48.4a 29.4a 34.2a 53.5a 7.3a 8.6a 8.6a 18.6 b point. These larvae had to come from Aug.21(R4) . . 39.6a 33.5a 50.1a 28.9a 35.5a 17.6a 28.7a 17.8a eggs laid before the treatment since the Aug.26(R5) . . 38.9a 45.8a 34.8a 42.5a 42.9a 63.4a 73.0a 41.4a Sept.9(R5) .. . 25.8a 26.7a 28.2a 29.4a 47.8a 51.0a 76.1a 37.4a egg stage requires 6.7 days at the Sept.19(R6) . . 23.1a 31.4a 21.1a 25.1a 32.4a 46.3a 72.3a 27.4a prevailing temperature of 20° 0.^ This Green cloverworm parasites finding supports the contention that Trichogramma sp. Braconid parasites^ parathion has no ovicldal activity (1). July30(R1).. . .2a .7a 3.7a .8a .7a .4a .7a .Oa The August 12 collection from the Aug.6-8(R2) . . .Oa .Oa .la 2.3 b .Oa .Oa .Oa .6a treated field (10 days posttreatment) Aug.12(R3) . . .7a .9a 1.0a 2.9 b .4a .5a .la .4a also had a high proportion of 1st instars Aug.21(R4) . . .4a .4a 1.1a 1.6a .Oa .3a .3a .8a (79 pet). These 1st Instars had to come Aug.26(R5) . . 2.2a 1.4a 2.9a 2.0a 1.0a .8a .4a 1.8a from eggs laid after the application. Sept.9(R5) .. . .8a .9a 1.2a 1.0a .6a .3a 1.3a 1.2a Sept.19(R6) . . .Oa .2a .7a .Oa .la .4a 1.0a .Oa Thus, either the moths also are tolerant Green cloverworms of the Insecticide or they moved back in- D-Vac-samples to the field In considerable numbers July30(R1).. . 5.2a 4.8a 11.9a 5.9a within a few days. Aug.6-8(R2) . . 3.8a 4.1a 1.5a 18.6 b The 1st instars present on August 8 Aug.12(R3) . . 4.5a 9.7a 6.7a 39.5a should have been 2d Instars by August Aug.21(R4) . . 35.2a 29.0a 35.8a 23.0a Plant-shake samples 12. If so, the ratio of August 12 2d's (23) Aug.26(R5) . . 57.2a 50.8a 40.0a 21.1a Sept.3(R5) 12.2a 11.9a 10.8 b 6.8 c to August 81st's (77) would estimate Sept.9(R5) .. . 36.6a 26.6a 28.5a 14.0a Sept.9(R5) 26.0a 21.0a 13.0ab 8.0 b survival during the 4-day period at about Sept.19(R6) . . 22.9a 19.9a 17.2a 9.3a Sept.16(R6) 21.0a 18.0a 21.0a 8.2 b Adult detritus feeders 30 percent. The ratio for the check field, Corticaria sp. Hippelates bistioppi Sabrosky 45 to 94, showed a higher rate of survival July30(R1).. . .2a .8a 3.1a .6a 4.1a 8.4a 9.2a 4.5a there, 52 percent (P< 0.025), despite its Aug.6-8(R2) . . .6a 2.9a 1.2a 1.2a .7a 1.2a 2.1a 5.6a higher predator population. The greater Aug.12(R3) . . 2.0ab 3.6 b .8a 10.2 c 1.7a 6.0a 7.0a 9.4a mortality In the treated field may have Aug.21(R4) . . 5.7a 4.3a 5.5a 5.1a 2.5a 1.6a 2.4a 6.5a been due to parathion residues remain- Aug.26(R5) . . 23.0a 41.5a 33.8a 27.7a 13.6a 18.4a 12.6a 21.6a ing on the plants. Sept.9(R5) .. . 27.3a 24.9a 17.6a 22.9a 4.4a 4.4a 4.4a 4.4a The August 21 sample (19 days Sept.19(R6) . . 18.2a 40.0 b 23.4a 18.5a 12.6a 2.3a 6.0a 15.0a posttreatment) showed a marked rever- Treated field received an aerial application of parathion (0.18 kg AI/0.4 ha) on Aug. 2. sal In trends (fig. 5). The population of Means within a row followed by the same letter are not significantly different at the 5 per- larvae in the treated field rose sharply, cent level. while the number In the check field 2See Literature Cited (3). declined. This was due primarily to ^Apanteies marginiventris (Cresson), Rogas noloptianae Ashmead, and Protomicropiitis facetosa Weed. changes In the populations of early in- stars—number of 1st's In the treated field rose 337 percent at the time it was declining by 55 percent In the check field. cloverwornns (fronn which the parasites Lepidopteran Larvae.—-D-Vâc emerge) were taken before spraying, Samples. The green cloverworm, and none were collected the week after, Plathypena scabra (F.), made up 93 per- so the parasites collected on August 12 cent of the larvae we collected. Its =*Marston, N. L [n.d.]. Data on file, Bio- probably migrated from surrounding numbers were low the week before we logical Control of Insects Research Labora- fields. applied the insecticide, and no dif- tory, USDA-ARS, Columbia, Mo. 65205. Larvae star per 3.05 row-m (7 pet of all larvae). /3.05 Row-M On the other hand, the plant-shake col- HU lections contained 7.1 x more 6th in- stars than the D-Vac collections (3.5 vs. 0.5 per 3.05 row-m). Differences in .1 :\ number of 3d to 5th instars in plant- / 1 ""\ shake and D-Vac samples were not .* 1 1 \ 30- significant. Evidence showed also that a ' 1 1 \ higher population existed in the center Check 1 1 \ 1 i of the treated field than existed at the 2.4x 1 outer sampling site on September 3 / 1 1 2.2x \ although the effect was small. Insecticide 1 1 Larval Prédation.—We noted no Treatment ? 1 1 20- -82% 1 1 difference between the treated and 1 1 check fields in survival of the introduced 1 1 1 1 i 1st instar cabbage loopers before treat- / -84% 1 A- ^""^V ment (table 2), nor did we note any dif- i /\ ference 3 to 4 days posttreatment (Aug. 1 * Treated Stage 5 to 6). This finding seems inexplicable 10- 1 / R5 1 / at first because of the great reduction in number of predators in the treated field ***••••• \ (fig. 4). The low rate of survival in the i- treated field, however, may have been / caused by persistence of insecticide o-J 1 1 1 I 1 1 residues on the plants, as is evidenced 26 6 8 12 25 1 9 19 also by data on the green clovenA/orm. July August September Effect of the low predator populations FIGURE 5.—Seasonal trend of populations of green cloverworm larvae in was more apparent on the later sampl- parathlon-treated and untreated soybeans. ing dates. On August 14 to 15,1st instar survival was 1.5 x higher, and on August 22 to 23, it was 1.4 x higher in The increased number of 1st in- Plant-Shake Samples.—-The the treated field. stars in the treated field probably was primary objective in taking plant-shake The reason for the pretreatment dif- not due to oviposition by a larger samples was to obtain larvae to ference in sun^ival of 4th instars (table 2) population of nnoths. Adults could not measure parasitism and disease, but is not apparent. The high rate of survival have developed there in 19 days at the the samples also provided estimates of and lack of difference between the prevailing temperatures, and the immi- populations. The treated field had a treated and check fields after treatment grant population, plus survivors, surely 2.2 X higher average population than indicate that the abundant predators was not higher than in the check field. the check field for the 3 weeks (Sept. 3 had little effect on larvae of this size. Thus, the big change had to be due to to 19) with a significant difference noted Larval Parasitism and Disease.— greater survival of eggs and early 1st in- for each sample (table 3). The green cloverworms on the plants us- stars in the treated field. All major The number of larvae collected by ed in the larval prédation tests (and the predator groups and Trichogramma the plant-shake technique was lower recovered cabbage loopers) were reared peaked in the check field the previous substantially than the number collected in the laboratory to determine their rates week, when eggs would have been ex- by D-Vac on September 9. The reason of parasitism and disease. Few green posed (table 1). for this was due to lower numbers of cloven/vorms were parasitized, and dif- The green cloverworm population early stages collected in the plant-shake ferences were not significant except for reached its peak in the treated field dur- samples. For example, D-Vac samples the pretreatment sample (table 3, whole- ing pod fill (fig. 5) when the soybeans are contained 8.51st instars per 3.05 row-m plant collections). A few cabbage looper most sensitive to defoliation (17). The (42 pet of all larvae) while the plant- larvae were parasitized by tachinids. population averaged 2.3 x higher in the shake samples contained only 0.81st in- None of the green cloverworms werQ in- treated field than in the check field when the two sets of data (Aug. 26 and Sept. 9) were analyzed together (P< 0.005) although differences for in- TABLE 2.— Percent survival of introduced cabbage looper larvae in dividual weeks were not significant parathion-treated and untreated soybeans, Columbia, Mo., 1974^ /table 1). Percent survival of cabbage loopers (24 h) Sweep-Net Samples.—By late growth 1st instars 4th instars August, a resurgence of green clover- stage^ Treated Check Treated Check worms was occurring in the treated Pretreatment field. We tested the generality of the July30-31 (R1) 40.0a 35.7a 65.7a 87.1 b resurgence during the week of Posttreatment September 1 to 7 (mid-R5) by taking Aug.5^(R2) 37.9a 30.7a 95.7a 87.1a sweep samples in each quadrant of Aug.14-15(R3) 52.9a 35.0 b 81.7a 84.3a each field. We found no differences Aug.22-23(R4) 56.4a 41.7 b 60.0a 51.7a between quadrants within either field, The treated field received an aerial application of parathion (0.18 kg AI/0.4 ha) on Aug. 2. but the treated field had 1.8 x more Paired means followed by different letters are significantly different (P<0.05). lan^ae than the check (P < 0.001 ). ^See Literature Cited (3). TABLE 3.—Percent parasitism and disease of green cioverworms in Discussion parathion-treated and untreated soybeans, Coiumbia, IMo., 1974' Our experiment showed that an ap- plication of insecticide to soybeans at Date and Parasitism Disease^ midseason can have detrimental ef- growth stage^ Treated Untreated Treated Untreated fects. Populations of predators and Whole-plant collections parasites of potential pests are reduced July31 (R1) 66.7(6) a 0.0(7) b 0.0(6) a 0.0(7) a greatly, and that can allow a resurgence Aug.6(R2) 0(1) a 4.0(25)a .0(1) a .0(25)a of lepidopteran larvae to more than dou- Aug.15(R3) .0(10) a 13.6(44)a .0(10) a .0(44)a ble the level in an untreated field. Aug.23(R4) 14.3(14) a 8.3(12)a .0(14) a .0(12)a Plant-shake samples We are fortunate in Missouri to Sept.3(R5) 20.9(196)a 28.6(21)a 7.7(196)a 19.1(21)a have great potential for biological con- Sept.9(R5) 16.0(119)a 12.5(64)a 27.7(119)a 42.2(64) b trol of the green cloverworm (6). In our Sept. 16(R6) 21.0(186)a 22.5(49)a 28.0(186)a 26.5(49)a test, these parasites and predators were The treated field received an aerial application of parathion (0.18 kg AI/0.4 ha) on Aug. 2. able to recover rapidly from the effect of Figures in parentheses are the number of larvae on which the percentages are based. Paired the insecticide and to suppress the percentages not followed by the same letter are significantly different (P<0.05). resurgent population of green clover- ^See Literature Cited (3). worms before they reached the last ^Nomuraea rileyi (Farlow) Sampson. stages, a time when cioverworms do most of the damage to the plants. Soybean growers in Southern States more often encounter pest populations that may reduce yield. fected with the fungus Nomuraea rileyi population in the treated field rose to Previous tests show that these popula- (Farlow) Sannpson, but on August 23,2 the level in the check, demonstrating tions can be reduced effectively by in- of the 31 4th-instar T. ni in the check again the remarkable ability of the in- secticides, but patterns of resurgence field and 1 of the 42 in the treated field sects to recover from the effects of the have been encountered similar to ours were infected. insecticide. (1115,19). When we noted that larval resur- The population of H. bishoppi, one Stage of growth seems to be a gence was occurring in the treated field, of several common acalyptrate Diptera critical factor. No study has we started the plant-shake sampling to in the ecosystem, did not vary signifi- demonstrated an increase in yield after obtain nnore larvae to estimate accu- cantly among plots on any sampling treatment at the flowering or early pod- rately the parasitism and infection by date, but the same trend occurred 3 set stages (R2-R3), which is due partly to N. rileyi. Parasitism did not differ be- weeks in a row after treatment. When the soybean plant's remarkable ability tween fields, but incidence of the analyzed as a whole, the inner- and to tolerate defoliation and depodding at fungus infection did. The check field middle-treated field plots had only 32 these early reproductive stages (17,18). had 1.5 X more infected larvae on percent as many flies as the check field We also must consider, however, that September 9 (late R5), while the 2.5 x during the 3-week period (P< 0.025) while when pests do surpass existing difference on September 3 was close to the population in the outer sampling economic thresholds at these early significance (P< 0.10). The lower rate of area in the treated field was in- stages, benefits from treatment may be infection in the treated field may have termediate. outweighed by the damage done by been caused by the delay of the early Percent Défoliation and resurgent populations. stages of the epizootic cycle by the in- Yield.—Despite the resurgence of green The key stage for insect control secticide, either by reduction of the cioverworms in the treated field, we seems to be late R4 or early R5 (the larval population (9) or effect of the noted no difference in percentage of point at which the pods are elongated parathion on the conidia (5). defoliation (3.9 pet in the treated field vs. and seeds can just be felt). Controlling Secondary Pests.—The parathion 3.2 pet in the check). The reason for this larvae or stink bugs at this stage application reduced populations of was due to the great mortality of cater- prevents damage during the critical pod- thrips by 86 percent; leaf hopper adults, pillars caused by prédation, parasitism, fill stages (R5-R6); yet, pest resurgence 91 percent; leafhopper nymphs, 95 per- and disease. The population of 6th in- would rarely be a problem because most cent; and whiteflies, 84 percent. Popula- stars, which accounts for about 75 per- varieties would be physiologically tions then gradually increased, but we cent of the defoliation (16), averaged on- mature before any resurgent pests found no evidence of resurgence of ly 3.3 larvae per 3.05 row-m in the treated reached the damaging late instars. these species. field and 2.6 larvae per 3.05 row-m in the We suggest that farmers or pest- Detritus Feeders.—We selected a check field during growth stages R5-R6 management specialists concentrate on lathridiid beetle, Corticaria sp., and a (plant-shake samples, Sept. 3,9, and 23). middle-sized larvae in sampling for chloropid fly, Hippelates bishoppi Soybeans are most sensitive to defolia- lepidopteran pests at these stages (late Sabrosky, to evaluate the effect of the tion during these stages, but the R4-early R5). Mature larvae already insecticide on adults of insects involved numbers were far below 68 to 79 larvae would have done most of their damage, in the breakdown of organic matter. The per 3.05 row-m, the economic threshold and counts of small larvae may be population of Corticaria was low the given for 76-cm rows (17). misleading because many of them week after treatment, and no effect was Yield did not differ significantly, would be killed by biological control demonstrated (table 1); however, a averaging 2,095 kg/ha in the check fields agents before maturing. reduction in the treated field was record- and 1,646 kg/ha in the treated fields. The ed the following week as the population least significant difference was high in the check began to rise toward the (467 kg/ha) because of variations in peak in late August. Subsequently, the stand and soil type within the fields. Literature Cited (8) Lindgren, P. D., and D. A. Wofenbarger. (15) Shepard, M., G. R. Carner, and S. G. (1) Chalfant, R. B, J. W. Todd, and 1977. Competition between Turnipseed. B. Mullinix. Trichogramma pretiosum and Orius 1977. Colonization and resurgence 1979. Cabbage looper: Ovicidal ac- insidiosus for caged tobacco bud- of insect pests of soybean in tivity of pesiticides in the worms on cotton treated with chlor- response to insecticides and field laboratory. Journal of Economic dimeform sprays. Environmental isolation. Environmental En- Entomology 72:30-32. Entomology 5:1049-52. tomology 6:501-6. (2) Craig, W. S., K. E. Brown, J. L Huggans, (9) Livingston, J. M., W. C. Yearian, and S. Y. (16) Stone, J. D., and L P. Pedigo. and others. Young. 1972. Development and economic in- 1974. Insect control recommenda- 1978. Effect of insecticides, jury level of the green cloverworm on tions. Missouri Cooperative Exten- fungicides, and insecticide- soybean in Iowa. Journal of sion Sen/ice, 156 p. fungicide combinations on develop- Economic Entomology 65:197-201. (3) Fehr, W. R., C. C. Caviness, D. T. ment of lepidopterous larval popula- (17) Thomas, G. D., C. M. Ignoffo, K. D. Biever, Burmood, and J. S. Pennington. tions in soybean. Environmental and D. B. Smith. 1971. Stage of development descrip- Entomology 7:823-8. 1974. Influence of defoliation and tions for soybeans, Glycine max (L.) (10) Marston, N. L, G. D. Thomas, C. M. depodding on yield of soybeans. Merrill. Crop Science 11:929-31. Ignoffo, and others. Journal of Economic Entomology (4) Greene, G. L, W. H. Whitcomb, and R. 1979. Seasonal cycles of soybean ar- 67:683-5. Baker. thropods in Missouri: Effect of (18) C. M. Ignoffo, D. B. Smith, and 1974. Minimum rates of insecticide pesticidal and cultural practices. C. E. Morgan. on soybeans: Geocoris and Nabis Environmental Entomology 1978. Effects of single and sequen- populations following treatment. 8:165-173. tial defoliations on yield and quality Florida Entomologist 57:114. (11) Morrison, D. E., J. R. Bradley, Jr., and of soybeans. Journal of Economic (5) Ignoffo, C. M., D. L Hostetter, C. Garcia, J. W. Van Duyn. Entomology 71:871-4. and R. E. Pinnell. 1979. Populations of corn earworm (19) Todd, J. W., N. A. Minton, and 1975. Sensitivity of the en- and associated predators after ap- P. D. Dukes. tomopathogenic fungus Nomuraea plications of certain soil-applied 1972. Infestations of phytophagous rileyiXo chemical pesticides used on pesticides to soybeans. Journal of insects on soybeans following soybeans. Environmental En- Economic Entomology 72:97-100. applications of DuPont 1410 foliar tomology 4:765^. (12) Newsom, L. D. sprays and other insecticides ap- (6) N. L Marston, B. Puttier, and 1967. Consequences of insecticide plied to the soil. Journal of others. use on non-target organisms. Economic Entomology 65:295-6. 1976. Natural biotic agents control- Annual Review of Entomology (20) and L W. Morgan. ling insect pests of Missouri soy- 12:257-286. 1972. Effects of hand defoliation on beans, p. 561-78. In Lowell D. Hill, (13) Price, J.F. yield and seed weight of ed., World Soybean Research. In- 1978. Calosoma sayi: Seasonal soybeans. Journal of Economic terstate Printers and Publishers, history and response to insecticides Entomology 65:567-70. Inc., Danville, III. in soybeans. Environmental En- (21) Turnipseed, S. G. (7) Johnson, D. W., L P. Kish, and G. E. Allen. tomology 7:359-63. 1972. Response of soybeans to 1976. Field evaluation of selected (14) and M. Shepard. foliage losses in South Carolina. pesticides on the natural develop- 1977. Striped eanA/ig, Labidura Journal of Economic Entomology ment of the entomopathogen, riparia, colonization of soybean 65:224-9. Nomuraea rileyi, on the velvetbean fields and response to (22) J. W. Todd, and W. V. Campbell. caterpillar in soybean. En- insecticides. Environmental En- 1975. Field activity of selected foliar vironmental Entomology 5:964-6. tomology 6:679-83. insecticides against geocorids, nabids, and spiders on soybeans. Journal of the Georgia En- tomological Society 10:272-7. Soil Arthropod Fauna (Part II) Abstract M. K. Hennessey and N. L Marston. 1982. Ecological Impact of Parathion in Soybeans. Soil Arthropod Fauna. U.S. Department of Agriculture, Technical Bulletin No. 1665.28 p. A survey of soil arthropods inhabiting soybean fields in central Missouri was conducted by soil-core sampling and pitfall trapping during July through October 1974. Two 8-ha fields, separated by 20 m with equal cropping schedules and similar soil types, were sampled weekly. One field was sprayed with a single foliar application of parathion at 0.45 kg Al/ha at the midf lowering stage, and the other was not treated. A total of 139 arthropod species were identified from the study. Populations of selected groups of soil arthropods were compared before and after treatment both within and between fields. Of 10 groups of arthropods sampled in soil cores, populations of 5 groups were reduced and 5 were unchanged within 1 to 3 months following treatment; populations of all groups were aggregated near the plants for most weeks, and 4 of the groups were aggregated in the upper 10.2 cm of soil during the study, irrespective of treatment. Pitfall trapping revealed that activity of three groups of ar- thropods was reduced, one was increased, and six were unchanged within 1 to 3 months following treatment. KEYWORDS: Soybeans, arthropods, sampling methods, faunal surveys, insecticides, pitfall trapping. Acknowledgments We wish to thank the following persons for identifying the soil arthropods: R. T. Allen (Carabidae), P. F. Bellinger (Collembola), O. L Cartwright (Scarabaeidae), W. S. Craig (Anthicidae, Cryptophagidae, Cucujidae, Lathridiidae, Scarabaeidae), N. B. Causey (Diplopoda), N. Downey (Ptiliidae, Staphylinidae), W. R. Enns (Meloidae), C. J. Good- night (Opiliones), R. D. Gordon (Orthoperidae, Scarabaeidae), J. M. Kingsolver(Pselaphidae, Ptiliidae, Scydmaenidae, Staphylinidae), R. D. Lund (Carabidae), A. S. Menke (Bethylidae), I. Moore (Staphylinidae), W. B. Peck (Araneae), B. Puttier (Noctuidae, Arc- tiidae), E. G. Riley (Chrysomelidae), T. J. Riley (Elateridae, larvae), D. R. Smith (Formicidae), J. W. Smith (Elateridae, adults), G. Sum- mers (Chilopoda), and S. E. Thewke (Acariña). Soil Arthropod Fauna (Part II) Michael K. Hennessey and Norman L Marston' Introduction tral Missouri. Soil samples taken to a Table 1.—Soil composition in core- Comprehensive surveys of ar- depth of 10.2 cm from both fields in- sampling areas of soybean thropod species associated with soy- dicated a generally loamy texture (Sar- fields, McBaine, Boone beans have been conducted in Ohio (1),' py) with slight variations in composi- County, Mo., 1974 Minnesota (20), Delaware (26), Maryland tion over the study area (table 1). Organic (29), Missouri (3), Arkansas (34), South Wheat and soybeans had been Location Texture Sand Sill Clay matter Carolina (6), and North Carolina (9), but planted In rotation in both fields for 4 Percent none included the soil fauna. A survey of years preceding the 1974-75 study. Untreated the soil arthropod fauna in soytjean Both fields were fallow the winter control fields in Iowa was conducted, and a list preceding the study, and no insec- plot Loam 43.6 41.6 14.8 2.0 of 208 genera collected was presented ticides had been used for 5 years. Parathion- (22). The only soil arthropod species that The fields were treated with an treated has been sampled extensively in soy- alachlor-linuron mixture as a field bean fields is the bean leaf beetle, preemergence herbicide and were Outer Sandy Ceratoma trifurcata (Forster). A planted to soybeans (var. Clark 63) in plot.. loam 57.6 29.6 12.8 2.2 sampling regimen was developed for the 91-cm rows on June 17,1974. Fields Middle eggs of the species in Illinois (36). The adjacent to the study fields contained plot .. Loam 45.2 33.6 2Í.2 2.2 effects of foliar insecticide applications corn and wheat. Average stand in the Inner on populations of nontarget soli ar- fields when measured at stage V7 (11) plot.. Loam 33.2 43.6 23.2 2.9 thropods in soyt)ean fields have not was about 16.5 soybean plants/row-m. been recorded. Early season weed species present Our studies at the Biological Con- were predominantly ivy-leaved morn- 3. We selected these areas to determine trol of Insects Research Unit In Missouri ingglory and field bindweed; late- whether distance from the field margin have focused on understanding the role season weeds included velvetleaf, affected population levels caused by of cultural practices in determining the sunflower, and common milkweed. movement back into the field after the species composition of the arthropod Both fields received light mechanical insecticide treatment. The outer plot community in soybean fields. One such weed cultivation at stage V4 on July 9 was located atxjut 50 m, the middle plot cultural practice is the use of parathion and stage R5 on August 27. One field about 100 m, and the inner plot about in foliar spray treatments as recom- was treated with a single application 150 m from the nearest field margin. mended for outbreaks of some of parathion, by airplane, at 0.45 kg-ha phytophagous Insects. on August 2,1974, during the We conducted an experiment dur- midf lowering stage (R2); the other ing the 1974 growing season to deter- field served as an untreated control. mine effects of parathion treatment on None of the yields differed significant- populations of nontarget arthropods liv- ly. They averaged 2,095 kg/ha In the ing in the soil. This study identified soil control field and 1,646 kg/ha In the arthropod species that were present in treated field. The least significant dif- soybean fields, compared population ference was high (467 kg/ha). It was patterns of soil arthropods in a caused by variations in stand within parathion-treated and an untreated field, the two fields. and measured the distribution of populations horizontally within and be- tween plant rows and vertically in the Sampling Methods soli. Soil-Core Sampling. We obtained Study Area cores 8.9 cm diameter and 10.2 cm deep Two 8-ha soybean fields (0.63 L) with a cylindrical steel sampling separated by 20 m were used for this tool (figs. 1 and 2). This tool, constructed study. The fields were located on the in our laboratory, closely resembled a fiat floodpiain along the Missouri commercially available golf-green corer. River in McBaine, Boone County, cen- A wooden piston attached to a slide within the cylinder functioned as a depth guage and core ejector. 'Hennessey is a graduate student, We took samples from three 30-m Department of Entomology, P.O. Box 5215, square plots within the treated field and North Carolina State University, Raleigh, one 30-m square plot in the control field. N.C. 27650; and Marston is a research en- tomologist. Biological Control of Insects Each sample consisted of 10 ag- Research Unit, Agricultural Research Service, gregated cores with a combined volume U.S. Department of Agriculture, P.O. Box A, of 6.3 L The cores were taken from a Columbia, Mo. 65205. wide area within each plot. The three BN 49357 'Italicized numbers in parentheses refer treated field plots correspond to the FIGURE 1.—Soli-core sampling at v\/ithin- to Literature Cited, page 23. outer, middle, and Inner areas In figure row site in soybean field. sides of the bucket with saltwater from a thropods In vials in 80 percent ethanol squeeze bottle. We then transferred ar- along with specimens collected from thropods and plant debris from the the 4- and 12-mesh sieves. The extrac- 100-mesh sieve to a lidded 950-ml tion left the specimens In good condi- polyethylene cup to prevent their escape. tion for identification. The xylene extrac- Time for extraction of one sample was tion step varies in the efficiency with about 0.5 h. The efficiency of the which it removes different types of ar- saltwater flotation technique for extrac- thropods from debris (appendix 2). ting various groups of arthropods from Because we collected such a great our samples was evaluated (appendix 1). variety of arthropods during the study, We washed the organic matter ex- we considered the following 10 broad, tracted from the sample through 4-, 12-, easily recognized taxa for the popula- and 100-mesh sieves. Material from the tion analysis: Poduroid Collemtx)la 4-and 12-mesh sieves was floated on a (Hypogastrura pannosa, Onychiurus en- sucrose solution (sp. gr. 1.17) in a white carpatus, Folsomia hoffi, and Pro- enamel pan and examined with the isotoma minuta), nymphs and adults; unaided eye for larger arthropods. Collembola—Entomobryidae, nymphs Material from the 100-mesh sieve was and adults; Diplura—Japygldae, mixed with water to make a 100-ml sluny nymphs and adults; Coleóptera— and stored frozen in lidded polyethylene Chrysomelidae, larvae and pupae; Col- cups until further extraction after the eóptera—except Chrysomelidae, larvae method of Marston and Hennessey (23). and pupae; Coleóptera—Staphylinidae, We used xylene (sp. gr. 0.86) to ex- adults; Coleóptera—except tract microarthropods from the organic Staphylinidae, adults; Lepidoptera, lar- debris from the 100-mesh sieve. Before vae and pupae; Díptera-Nematocera, extraction we thawed each sample, larvae and pupae; Díptera-Cyclor- added about 50 ml of xylene, and then rhapha, larvae and pupae. shook the sample in the cup vigorously We computed mean numbers of for about 10 s. The arthropods floated in arthropods and standard errors for the the xylene layer above the plant debris, 10 groups on a monthly basis for each which remained in the water. We then of the sampled plots. For July, five refroze the sample to trap the organic sampling dates were analyzed and debris in the ice and decanted the un- sen/ed to compare the fields before frozen xylene layer onto a medium- treatment. Four posttreatment sampling BN 49358 FIGURE 2. -Soil-core sampling tool with porosity filter paper in a 7.50-cm dates were taken in August and In soil core. Büchner funnel that was attached to a September, and three were taken in 1,000-ml vacuum flask. Residual xylene October. We derived means from the In each plot, we took two samples was removed immediately from the filter weekly samples. Population changes within the row, 0 to 8.9 cm from the paper and arthropods by rinsing with 80 from week to week were expected to be plant stems, and two samples midway percent ethanol. We stored the ar- proportionate between plots before and between the rows, 41.0 to 45.5 cm from the plant stems. This distinction be- tween samples allowed us to measure aggregation of arthropod populations in one or the other habitat. We com- pared data from the within-row and between-row samples to measure the difference in habitat preference. We began sampling when the soy- beans were in the unifoliate stage (VI; July 2,1974) and continued through harvest maturity (R8; October 23,1974). Samples were removed from the fields in 15-L lidded cans, stored at room temperature, and processed within 72 h. Arthropods were extracted from samples by modifying a technique of Salt and Hollick (32) and Salt et al. (33). Core samples, which had remained more or less intact in the cans, were crumbled manually and placed into 6 L of saturated NaCI solution (sp. gr. 1.19) in a 15-L can. Floating organic portions of the soil were decanted onto a 100-mesh sieve (U.S. Standard Sieve Series). Two additional décantations of the sample, following FIGURE 3.—Diagram of study area, McBaine, Boons County, Mo., 1974. Check vigorous hand stirring, were carried out. outer, middle, and inner areas were sampled with pitfalls and cores. Only pitfall Between décantations, we rinsed the samples were taken in the wheat field margin and road margin areas. 10 after treatment except where an effect 100-mesh sieve and placed them in 80 from treatment occurred. Means and percent ethanol for storage. The ar- standard errors for within-row and thropods were collected in good condi- laetween-row samples were calculated tion for identification. for all plots combined within each Species collected in pitfall traps month. We transformed all data to were grouped into 10 broad taxa as Vx + 1 for factorial analysis of follows: CollembKJia—/sofoma viridis variance (P = 0.05). Where significant F and Tomocerus flavescens, nymphs and values were found, we used Duncan's adults; Orthoptera-Gryllidae, nymphs New Multiple Range Test to compare and adults; Coleóptera—lan/ae; Col- means. eóptera—Carabidae, adults; Coleóptera On July 9 (V3), August 6 (R2), and —Staphylinidae, adults; Coleóptera— Septemtjer 3 (R5), 1974, we took addi- Anthicidae, adults; Coleóptera—other tional soil samples, consisting of eight families, adults; Hymenoptera—Fbrm- cores per sample, to depths of 10.2,20.4, icidae, adults; Araneae—Lycosidae, im- and 30.6 cm in the control plot to deter- matures and adults; Araneae—other mine whether the species composition families, immatures and adults. changed with vertical sampling depth. BN 49359 Mean numbers of arthropods col- FIGURE 4.—Cups nested to make a pitfall lected and their standard errors were These samples also were useful in trap. determining the texture of the soil at calculated for each arthropod group and those depths and gave us an indication sampling date. This was done for the of what proportions of the various ar- treated field and the control field, as thropod groups were included in our cup to facilitate removal without the well as for each field margin. We con- standard-sampling depth of 10.2 cm. We hole collapsing (fig. 4). The lip of the col- ducted two analyses of variance. The determined mean values for each ar- lection cup rested at ground level, and primary analysis tested for differences thropod group at each depth by combin- about 50 ml of soapy water was added between the treated- and control-field ing data from the three sampling dates as the trapping medium. We placed four captures for each month. A second and expressing the mean as a propor- traps in each of the three plots in the analysis, designed to measure migra- tion of the total found at all depths. The treated field and four traps in each of tion of arthropods into the treated field, standard error of each proportion was three areas in the control plot. This compared monthly means for the con- calculated by normal approximation. design permitted us to measure the ef- trol plot, the outer-, middle-, and inner- On May 2,1975,6.5 months after fect of distance from the field margin on treated plots, the wheat field margin, the soybeans were harvested and the rate of capture of those organisms and the road margin. We transformed wheat was planted, we took two migrating into the field after the insec- the data to Vx -t- 1 and employed Dun- samples from each plot in the treated ticide treatment. In addition, we placed can's New Multiple Range T^st where field to determine whether the popula- three traps along each of the two significant F values were present. tion levels or species composition had margins of the treated field; one margin Representative specimens from changed after the land was rotated to bordered the road and the other core and pitfall collections were pinned, wheat. We compared the number of ar- bordered the wheat field (fig. 3). Traps stored in 80 percent ethanol, or mounted thropods collected on the last seasonal within a group were spaced 3 m apart on slides (Meloidae larvae) for identifica- sampling date (October 23) and the May and were opened for one 24-h period tion. We identified some specimens us- samples. A Student's t-test was per- weekly from July 2 (VI) to October 16 ing available keys and reference collec- formed on population means for each (R7), 1974. They were covered tightly be- tions from the University of Missouri En- arthropod group. tween sampling periods. tomology Museum, but we classified Pitfall Trapping. Pitfall traps con- We recovered specimens from the most specimens to the lowest taxon sisted of polyethylene cups 12 cm deep field by removing the trap from the possible and forwarded them to with an 11-cm opening diameter located ground and transferring the contents to specialists for identification. Voucher midway between rows of plants. The baby food jars. In the laboratory, we specimens were placed in the University collection cups nested inside another strained the contents through a museum. Taxonomic List of Soil Arthropods Collected Diplopoda (C,P;0) Polydesmida The following soil arthropods were identified in collec- Polydesmidae: Pseudopolydesmus minor (BoWman); P. serrata (Say) tions from soytjean fields taken during this study. Insects Julida such as grasshoppers, thrips, and leafhoppers, which were Paraiulidae: An/u/us fco/Zman/Causey collected occasionally in pitfalls or cores, are not included in Cleidogonidae: Cleidogona sp. (immature) this list because they were collected in greater numbers from Chilopoda(C;J-0,M) the foliage in D-Vac, plant-shake, or sweep net samples and Geophilomorpha they appear in listings of fauna derived from those studies. Geophilidae: Arenophllus bipuncticeps (Wood) This exclusion does not preclude the possibility that many of Dignathodontidae: Strigamia chiortophila (Wood) these insects spend part of their life cycles within the soil Lithobiomorpha habitat. Notations in parentheses indicate collecting data as Lithobiidae: Nadabius ameles Chamt>erlin Pauropoda (C;J-S); undetermined, possibly several species. follows: Core sample (C), pitfall sample (P), July (J), August Arachnida (A), September (S), October (O) 1974, and May (M) 1975. All Pseudoscorpionida (C;J-0,M); undetermined, 1 sp. specimens were adults, unless otherwise noted. Five classes Opiliones(P;A-0) represented by at least 18 orders, 66 families, and 150 genera Phalangiidae: Leiobunum crassipaipe Banks; L flavum Banks; were collected, and 139 species were identified. L nigripes Weed; Leiobunum sp. 11 Arachnida-Continued Insecta-Continued Acariña (C;J-0,M. Only the most frequently collected fannilies were Coleoptera-Cont i n ued identified.) Carabidae:-Cont ¡ n ued Acaridida Patrobus (Neopatrobus) longicornis Say (P;S-0); Pterosti- Acaridae: undetermined, several spp. chus (Abacidus) permundus Say (P;S-0); P. (Euferonia) Tyroglyphidae: undetermined, several spp. stygicus Say (P;S); P. (Poecilus) chalcites Say (P;J-0); Oribatida P. (Poecilus) sjp. (P;J-0); Scarites substriatus Haldeman Oribatidae: undetermined, several spp. (P;J-A); S. subterraneus (F.XP;S); Stenolophus carbonarias Phthiracaridae: undetermined, several spp. Dejean (P;S); S. ochropezus Say (P;S); Tachys (Tachyura) Araneae anceps LeConte (P,C;J-0); Tachys sp. (P,C;J-0) Dictynidae: Dictyna sp. {immature, C;M) Histeridae: undetermined, 1 sp. (P;S) Micryphantidae: Erigone autumnalis (Emerton) (C,P;J-0); Riliidae: Acratrichus sp. (C;J-0,M); Ptinella so. iC;J-0,M) Eperigone trilobata (Emerton) (C,P;J-0); Grammonota Staphylinidae: Anotylus insignitus Graven horst (P,C;J-S); inornata {EmerXon) (C,P;J'0); undetermined, 1 sp. Apocellus sphaericollis Say (P,C;J-0); Apocellus sp. Tetragnathidae: Pachygnatha tristriata {C.L Koch)(P;J) (P,C;J-0); Carpelimus sp. (P,C;J-0); Gyrohypnus emmesus Agelenidae: Agelenopsis pennsylvanica (C.L. Koch) (P;S) Gravenhorst (P,C;J-0); Heterothops pusio LeConte Lycosidae: Lycosa annexa (Chamberlin and Ivie) (immature, P;S); (P,C;J-0); Lathrobium sp. (P,C;J-0); Lobrathium dimidiatum L punctulata (Hentz) (P;0): Pardosa milvina (Hentz) (P;J-0); Say (P,C;J-0); L longiuscula Gravenhorst (P,C;J-0); P. saxatilis (Hentz) (P;J-0); Pirata insularis (Emerton) (P;A); Neobisnius sp. (P,C;J-0); Omalium sp (P,C;J-0); Osorius Schizocosa ocreata (Hentz) (P;A); S. saltatrix (Hentz) (P;J) latipes Gravenhorst (P,C;J); O. planifrons LeConte (P,C;J); Oxyopidae: Oxyopes salticus (Hentz) (P;J-0) Philonthus alumnus Erichson (P,C;J-0); Philonthus 2 spp. Gnaphosidae: Calíllepis imbecilla (Keyserling) (P;A); Drassylus (P,C;J-0); Quedius molochinus Gravenhorst (P;0); Quedius depressus (Emerton) (P;J); Zelotes laccus (Barrows) (P;J); sp. (P;0); Rugilus dentatus Say (P,C;0); Scopaeus exiguas Zelotes sp. (immature, P;J) Erichson (C;S); Sipalia (Lepinga) sp. (C; J-0); Stenus callosas Clubionidae: Trachelas deceptus (Banks) (P;A) Erichson (P,C;A); S. stygicus Say (P,C;A); Stenus sp. (P,C;A); Theridiidae: Robertas livida (Blackwall) (P;S); undetermined, Tachyporus jocosus Say (P,C;J-0); T. nitidula F. (P,C;J-0); 1 sp. (immature, P;S) Tachyporus 2 spp. (P,C;J-0) Pisauridae: Pisaurina brevipes (Emerton) (P;0) Lathrobini: undetermined, several spp. (P,C;J-0) Thomisidae: Thanatus formicinus(Clerck) (P;0); Xysticus Aleocharinae: undetermined, several spp. (P,C;J-0) gulosus (Keyserling) (P;0); X. triguttatus Keyserling (P;0) Pselaphidae: Euplectus sp. (C;J-0,M); Rhexius sp. (C;J-0,M) Salticidae: Eris marginatus (Walckenaer) (P;J); Evarcha hoy i Orthoperidae: Orthoperus sp. (C;J-0,M) (Peckham) (P;J); Habronattus coronatus (Hentz) (P;0) Elateridae: Aeolus mellillus com is (LeConte) (P; J-0); A. m. mellillas Insecta (Say) (P; J-0); Conoderus auritus Herbst (P; J-0); C. bellus Say Collembola (P;J-0); C. lividus (DeGeer) (adult, P;J-0: larva, C;J-0); Poduridae: Hypogastrura pannosa (Macnamara) (C;J-0,M) C. vespertinus (F.) (adult, P;J-0: larva, C;J-0); Melanotus Onychiuridae: Onychiurus encarpatus Denis (C;J-0,M) depressus (Melsheimer) (adult, P;J-0: larva, C;J-S); Isotomidae: Folsomia hoff i ScoXX (C;J-0,M); Isotoma viridis Negastrlus pectoralis (Say) (C,P;J-0) Bourlet (P;J-0); Proisotoma minuta (Tullberg) (C;J-0,M) Heteroceridae: undetermined, 1 sp. (P;A) Entomobryidae: Entomobrya 2 spp. (C;J-0,M); Orchesella sp. Cryptophagldae: Anchicera ephippiata Zimmerman (C;0); (C;J-0,M); Pseudosinella violenta (Folsom)(C;J-0,M); A. nubipennis Say (C;0) Tomocerus flavescens (Tullberg) (P;J-0) Cucujidae: Telephanus velox Haldeman (C,P;J-0) Sminthuridae: Sminthurinus sp. (C;J-0,M) Scydmaenidae: Euconnus sp. (C;S) Thysanura Phalacridae: Stilbus apical is (Melsheimer) (P,C;J-0) Lepismatidae: undetermined, 1 sp. (P;J) Nitidulidae: undetermined, 1 sp. (P;J) Diplura Lathridlidae: Melanophthalma sp. (P,C;J-0,M) Japygidae: undetermined, 1 sp. (C;J-0,M) Anthicidae: ^caA7f/7/A7iys myrmecops (Casey) (C,P;J-0,M); Anthicas Orthoptera cervinas LaFerté-Sénecterè (C,P;J-0,M); A. ephippium Gryllidae: Gryllus probably several spp. (P;J-0); Allonemobius LaFerté-Sénecterè (adult, C,P;J-0,M: larva, C,P;J); A. latalen- fasciatus (DeGeer) (P;J-0) tus Casey (C,P;J-0,M); Notoxus murinipennis LeConte Hemiptera (C,P;J-0) Enicocephalidae: Systelloderes biceps (Say) (C;J-0) Mycetophagidae: Typhaea stercorea L (C,P;J-0) Cydnidae: Geotomus robustus (Uhler) (P;J); Pangeus bllineatus Meloidae: Epicauta lemniscata (F.) (P;S,0); £ (Macrobasis) (Say)(P,C;J-0) Immaculata Say (larva, P;J-0) Coleóptera Scarabaeidae: Aphodius prodromus (Brahm) (adult, C,P;J-0); Cicindelidae: Cicindela punctulata punctulata Olivier (P;J-A); A. femoralis Say (adult, C,P;J-0: larva, C;J-S); Ataenius C. repanda repanda Dejean (P;J-A); Megacephala virginica punctifrons Cartwright (adult, C,P;J-0: larva, C;J-S); (L.)(P;J-A) A. strigatus (Say) (adult, C,P;J-0: larva, C;J-S); Cyclocephala Carabidae: Acupalpus (Tachistodes) sp. (P;J); Agonoderus Immaculata Olivier (larva, C;A); Onthophagus hecate comma F. (P;J,S-0); Agonum (Circinalia) crenistriatus Panzer (P;J) L.eConte (P;A-0); A. (C.) punctiforme Say (P;A,0): Chrysomelidae: Altica ígnita llliger (P;J-0); Ceratoma trifurcata A. (Paragonum) placidum Say (P;S); Amara (Bradytus) (Forster) (larva, C;J-0,M); Chaetocnema confinus Cresson exarata Dejean (P;S); Anisodactylus (Anadaptus) (P;J-0); C. denticulata (llliger) (P;J-0); C. pulicaria (Melshei- sanctaecrucis (F.) (P;S-0); Bembidion (Notaphus) rapidum mer) (P;J-0); Diabrotica undecimpunctata howardi Barber LeConte (P;A-0); Bradycellus sp. (P;S); Calosoma (Callitropa) (larva, C;J-0,M); Dibolia borealis (Chevrolat) (P;J-0);D/so/7- externum Say (Adult P;A: larva P;S); Chlaenius (Anomo- ycha collata(F.)(P]ó-0) glossus) pusillus Say (P;J-A); Clivina bipustulata F. (P;J-A); Curculionidae: Hypera punctata (F.) (P;J); Sitona hispidula (F.) C. férrea LeConte (P;J); C. punctulata LeConte (P;J-A); (P;J); one species undetermined Colliurus pennsylvanica (L.) (P;A,0); Cratacanthus dubius Lepidoptera (Palisot de Beau vols) (P;J-A); Evarthrus sodalis collosus Arctiidae: Diacresia virginica (F.) (larva, P;S,0); Estigmene acres LeConte (P;J); Harpalus erraticus Say (P;A-S); H. (Drury) (larva, P;S,0) (Pseudophonus) faunus Say (P;J-A); H. (Megapangus) Noctuidae: Agrotis ípsilon (Hufnagel) (larva, C;A); Tetanolita caliginosus F. (P;J-S); H. (Pharalus) testaceus mynesalis (Walker) (larva, C;J-0,M); undetermined, several LeConte (P;J-S); H. (Pseudophonus) pennsylvanicus spp. (larva, C;J-0) DeGeer (P;J-0); Microlestes 2 spp. (P;J-A); 12 Insecta-Continued Insecta-Continued Diptera Hymenoptera Nematocera Mutillidae: undetermined, 1 sp. (P;0) Tipulidae: undetermined, 1 sp. (larva, C;A) Formicidae: (C,P;^}-0,M) Acanthomyops sp.; Crematogaster sjp.] Chironomidae: undetermined, several spp. (larva and pupa, Formica subsericea Say; Hypoponera opac/or (Forel); C;J-0,M) Lasius neoniger Emery: Pheidole bicarinata Mayr; Sciaridae: undetermined, several spp. (larva and pupa, Pheidole 2 spp.; Ponera pennsylvanica Buckley; Solenopsis C;J-0,M) molesta (Say) Brachycera Bethylidae: Dissomphalus sp. (P;S) Stratiomyidae: undetermined, 1 sp. (larva, C;A) Cyclorrhapha Anthomyiidae: undetermined, probably several spp. (larva and pupa, C;J-0,M) Results treated-f ield means for the month This group was aggregated within Soil-Core Sampling following treatment. We found dif- the rows to a significant degree in Poduroid Collembola. Coliembola ferences between fields in September, August (table 4). On August 20, when the made up 37 percent (10,155) of the but in October the treated-f ield popula- leaf canopy was closed, aggregation 27,447 specinnens collected in cores. tion was significantly higher (P< 0.01) was associated with leaf drop, which The poduroid group made up 83 percent than that of the control. was concentrated mainly within rows at (8,429) of all collembolans sampled. They consisted of the species Hypogastrura pannosa, Onychiurus en- Poduroid Other Collembola Coleóptera carpatus, Folsomia hoffi, and Pro- (larvae) isotoma minuta, all primarily saprophagous or feeding on minute soil 180- •—• Control organisms. (7). F. hoffi was the species o—o Porothion-treated most often collected. Weel 13 Table 2.—Rainfall, air temperature, Table 3.—Mean monthly soil arthropod populations in an insecticide- relative humidity, and soil treated and an untreated-soybean field at McBalne, temperature recorded during Boone County, Mo., 1974 study at McBaine, Boone County, Mo., 1974 Number of arthropods per 6.3 liters of soil in indicated area^ Untreated insecticide-treated' Sampling Rain- A ir Relative Soil Month control Outer Middle inner date falP temp. {C°y humidity(%)2 temp. Poduroid Collembola cm Max. Min. Max. Min. (Cy July 2 .. July*^'^ ... s3.55± 1.12a 3.05± 0.94a 0.90± 0.35 b 1.80± 0.69 b , 0.0 41 24 75 24 {') Aug 3.93 ± 1.28a .81 ± .44 b .62 ± .34 b 1.12 ± .46 b 9 .., 3.3 42 22 85 35 {') 16 .. Sept 3.87 ± 1.06a 14.50 ± 7.38a 13.12 ± 6.04a 4.37 ± 1.64a .2 35 15 80 25 {') Oct 44.16 ± 12.43 b 86.50 ± 17.68a 122.41 ± 27.84a 95.75 ± 22.91a 23 .. 0 37 15 80 25 W 30 .. Entomobiyidae .2 42 11 W « 25 July 3.20± .75a .85± .42 b .95± .35 b 1.20± .43 b Aug. 6 .. 1.1 23 16 100 45 24 Aug 3.93 ± 1.49a .93 ± .23 b 2.00 ± .59ab 1.56 ± .60 b 13 .. 4.3 35 18 82 39 23 Sept.* 3.25 ± 1.03a 2.62 ± 1.13a 1.37 ± .58a 2.25 ± .74a 20 .. .5 40 21 80 30 25 Oct 12.50± 3.47a 8.08± 4.12a 1.33± .81 b 4.33± 1,94 b 27 .. 8.8 30 20 80 60 25 Japygidae Sept. 3 . . 6.8 32 6 83 20 15 July 18.60 ± 3.14a 9.35 ± 1.82a 10.60 ± 1.43a 16.25 ± 3.06a 10 .. 0 37 18 83 35 20 Aug.* .... 36.12± 6.81a 18.62± 2.45 b 24.87± 4.95 b 21.62± 2.80 b 17 .. .4 40 11 83 26 17 Sept.*.... 19.93± 4.20a 6.25± 1.43 c 2.87± .68 d 11.87± 2.85b 24 .. 0 35 11 86 22 18 Oct.* 4.75± 1.46a 2.00± .71b .66± .28 c 1.00± .46 be Oct.1 .. 1.9 29 -2 90 15 12 Chrysomelidae (larvae and pupae) 9 .. .2 30 2 94 20 W July 15± .08a .15± .14a 0 ±0 a .05± .04a 16 .. 2.1 29 4 {') {*) 17 Aug.*.... 3.50 ± .93a .56 ± .27 c 1.43 ± .60 b 1.37 ± .47 b 21 .. 0 « « « « « Sept.*.... 3.06 ± .88a 1.18 ± .48 b .87 ± .35 b 1.62 ± .89 b ^Recorded for week ending with the Oct 25 ± .17a .08 ± .08a .50 ± .23a .25 ± „17a sampling date, Columbia Regional Airport, Coleóptera, except chrysomelidae Qarvae and pupae) Columbia, Boone County, Mo. July* 5.85 ± .92a 4.45 ± .67a 3.90 ± .61a 3.80 ± .84a ^Recorded at study site during 24-h Aug 4.50 ± 1.11a 4.43 ± .59a 3.06 ± .72a 2.62 ± .39a pitfall-trapping period. Sept 3.06 ± .54a 3.68 ± .63a 4.06 ± .59a 1.06 ± .39 b ^Average of 2 readings taken at 10.2-cm Oct 2.91 ± .78a 3.91 ± .74a 3.75 ± .55a 2.91 ± .77a depth at study site during period of core Staphyllnidae (adults) sampling. July 1.10± .30a .75± .22a .45± .15a .45± .22a ^Data unavailable. Aug 1.43± .66a 1.12± .25ab .50± .15 b .68± .23 b Sept 4.06± .66a 1.56± .30a 1.00± .20 b 1.00± .32 b Oct 1.41 ± .31a 3.16± .48a 3.25± .61a 1.66± .30a Coleóptera, except Staphyllnidae (adults) its onset. Populations became July 2.65 ± .95a 1.60 ± .42a .85 ± .22a 1.00 ± .41a distributed more evenly between Aug 2.56 ± .63a 2.43 ± .79a 2.00 ± .50a 1.62 ± .31a habitats on August 27 when cultivation Sept 2.31 ± .38a 1.56 ± .45a 1.37 ± .30a 1.00 ± .28a mixed the soil and caused a decrease in Oct 3.16 ± .71a 2.83 ± .54a 3.75 ± .76a 1.75© .47a population over all plots. We detected Lépidoptère (larvae and pupae) significant interaction between field July 05 ± .04a .05 ± .04a .10 ± .02a .10 ± .06a areas and row areas for August. Collem- Aug.* 43± .15a .87± .55a .68± .23a .37± .15a bolans were aggregated within rows in Sept 1.87 ± .53a 1.87 ± .'28a 1.12 ± .37a 1.06 ± .26a the control and inner plots during the Oct 91 ± .37a 1.75 ± .35a 1.41 ± .31a 1.41 ± .43a Díptera, Nematocera (larvae and pupae) month, but they were distributed more July 1.20± .32a 1.10± .29a .35± .14 b .10± .06 b uniformly between habitats in the outer Aug 1.62± .34a .75± .26a 1.18± .54a .56± .22a and middle plots. No preference for the Sept 1.62 ± .52a 1.56 ± .45a 3.06 ± 1.03a 1.62 ± .70a root-zone habitat was found for July, Oct.* 5.83± 3.12 b 6.16± 2.20 b 11.25± 3.24a 3.91 ± 1.20 b September, or October. Díptera, Cyclorrhapha (larvae and pupae) Entomobrydae. These collem- July* 1.20 ± .35 b 2.00 ± .46a 1.00 ± .37 b .90 ± .31b bolans, which inhabit an ecological Aug.* .... 3.62± 1.20a 3.93± 1.14a 4.00± 1.43a 3.62± .77a niche similar to that of the previous Sept 59.53 ± 39.40a 17.31 ± 2.68a 10.68 ± 1.96 b 4.87 ± 1.10 c group, were counted separately Oct 3.75± 1.31a 6.08± 1.63a 5.00± 1.54a 3.08± .84a because they possess a visible furcula, ^Control plot was located about 250 m ^Growth stages: July (V1-R1); Aug. which might allow greater mobility. from insecticide treated plots. Outer plots (R2-R5); Sept. (R5-R6); Oct. (R6-R8). See Entomobryids made up 17 percent were 50 m, middle plots 100 m, and inner Literature Cited (11). (1,726) of all collembolans sampled; plots 150 m from field margin. ^Parathion applied at 0.45 kg/ha by '»Mean and standard error of 3 to 5 Pseudosinella violenta was the species airplane on August 2,1974. weekly samples per month. Row means not most frequently taken. Weekly popula- ^'An asterisk following a month indicates followed by the same letter are significantly tion fluctuations for this group were significant interaction between sampling different (P<0.05), Duncan's Multiple Range similar to those of the previous group areas and weeks within the month. Test. (fig. 5), with a late-season peak of 19 adults and ¡mmatures/6.3 L in the con- trol field. Significantly higher numbers ferences between fields, therefore, to tained in the inner plot. On September were present in the control field than in the effect of parathion treatment. We 24, numbers collected in the control and treated plots before the pesticide ap- found sampling area-date interaction for outer areas were about tenfold more plication. This situation persisted until September. Collections were low for all than those in the middle and Inner plots. September (table 3); the reason was not plots on September 3, but by the third Aggregation within rows occurred apparent. We cannot attribute the dif- week, highest populations were main- during July and August (table 4), but no 14 Table 4.—Mean monthly soil arth- populations were aggregated for the re- economically important species: the ropod populations within nnaining months of the study. A field-row southern corn rootworm (16) ano the and between rows in fields interaction was present in July as ag- bean leaf beetle (17). Larvae of both of soybeans, McBaine, Boone gregation occurred between rows for species were present in our plots County, Mo., 1974 the outer plot and within rows for the although the proportion of each was not others. measured. Together with flea-beetle lar- Number of arthropods per 6.3 liters vae (Alticinae), they made up 2 percent of soil in indicated area' Japygidae. Japygids of a single undetermined species were the most (535) of the arthropods sampled. Popula- Within rows Between rows Month numerous of the groups sampled for the tions in the treated field reached two in- Poduroid Coiiembola first part of the season, comprising 30 sects/6.3 L during August, compared . 32.75± 0.63a 1.90 ± 0.55a July^ . percent (8,190) of all arthropods col- with eight insects/6.3 L in the control Aug.*^ 2.68 ± .72a .56 ± .22 b Sept.. 9.15 ± 3.19a 8.75 ± 3.78a lected. They are considered to be (fig. 5), which demonstrated a damping Oct... . 87.45 ±13.1 la 86.95 ± 17.87a predaceous on mites and collembolans effect of insecticide application on Entomobryidae (21). Numbers in both fields were af- populations. This decrease in larval July*. 1.97 ± .45a 1.05 ± .30 b fected by cultivation July 9 and August populations may have resulted from Aug. . 2.93 ± .83a 1.28 ± .30 b 27 (fig. 5) and increased steadily in July mortality of adults and decreased Sept.. 3.00 ± .80a 1.75 ± .37a and August with the consolidation of oviposition rather than from a direct ef- Oct... 8.37 ± 2.74a 4.75 ± 1.32a the litter layer. Populations began to fect of the insecticide on the larvae. The Japygidae decline in September, following rains difference between fields caused by . 17.40± 2.22a 10.00 ± 1.06a July.. and cool weather. treatment was pronounced for August Aug. . . 29.84 ± 3.95a 20.78 ± 2.55 b Sept.* . 11.06± 2.72a 9.40 ± 1.43a A significant difference (P<0.05) and September (table 3), but by October, Oct... 1.87 ± .57a 2.33 ± .77a between control and treated plots was populations had dropped to similar Chrysomelidae Qarvae and pupae) detected in the August samples (table levels in both fields, presumably July.. .15 ± .08a .02-»- .02a 3), indicating that this group was because of declining oviposition and lar- Aug.* 2.96 ± .53a .46 ± .23 b adversely affected by the insecticide val maturation. Sept.. 3.12 ± .60a .25 ± .12 b treatment of August 2. Monthly mean Interaction of sampling areas and Oct... .37 ± .14a .16 ± .09a populations in the control field remain- weeks was present for August and Coleóptera, except Chrysomelidae ed significantly (P< 0.05) higher than September. We collected very few larvae Oarvae and pupae) those of the treated plots for September during the first week of August; July.. 4.92 ± .57a 4.07 ± .53a Aug. . 4.71 ± .61a 2.59 ± .38 b and October. An interaction of sampling therefore, we found no difference be- Sept.. 3.46 ± .47a 2.46 ± .36 b areas and weeks was present for tween plots. By the second week, Oct... 3.16 ± .54a 3.58 ± .45a August, September, and October. On however, populations had risen in the Staphylinidae (adults) August 20, control populations exceed- control and inner plots but remained un- July.. .90 ± .14a .47 ± .13a ed by threefold those of the treated field. changed in the outer and middle plots. Aug. . 1.28 ± .22a .59 ± .14 b This increase corresponded with the Populations continued to increase in the Sept* 2.26 ± .35a 1.75 ± .32 b observation that the leaf-drop in the con- control while leveling off in the treated Oct... 2.12 ± .33a 2.62 ± .37a trol field preceded that in the treated plots. While populations dropped in the Coleóptera, except Staphylinidae (adults) field beginning on that date. On August control- to treated-plot levels on July.. 2.35 ± .53a .70 ± .14a 27, populations in the inner plot were September 3, they increased again to Aug. . 3.15 ± .46a 1.15 ± .24 b twofold more than those in the other significantly higher numbers than in the Sept.. 1.84 ± .26a 1.28 ± .25a plots. This trend carried over into treated field for the balance of the Oct... 3.66 ± .55a 2.29 ± .33a September, but on September 10, con- month. Lépidoptère trol field populations again increased to We found larvae aggregated within (lanfae and pupae) exceed ail other plots by twofold. rows during August and September July.. .12 ± .06a .02 ± .02a Populations were evenly distributed over (table 4). An interaction of field areas Aug. . .93 ± .29a .25 ± .07 b the plots in the initial October sample, and row areas occurred in August 2.21 ± .31a .75 ± .12a Sept.. because of the low numbers collected in Oct... 1.79+ .26a .95+ .??a but they declined more rapidly in the Díptera, Nematocera treated plots than in the control plot. the outer area samples, which (larvae and pupae) Japygids were more numerous within eliminated differences between habitats July.. .70 ± .18a .67 ± .17a rows than between rows (table 4) only in that plot for that month. Aug. . 1.06 ± .22a 1.00 ± .29a during August when their population Coleóptera, except Chrysomelidae Sept.. 2.56 ± .60a 1.37 ± .37a peak of 55 adults and immatures/6.3 L (larvae and pupae). This highly diverse Oct.*. 8.41 ± 2.23a 5.16± 1.32a occurred in the control plot. In group made up 7 percent (1,987) of the Díptera, Cyclorrtiapha September, populations in the outer plot arthropods collected. Aphodine (larvae and pupae) were concentrated more between rows scarabaeids (10 pet, 198), anthicids (4 1.60 ± .32a .95 ± .19 b July.. than within, bringing about a field area- pet, 87), and elaterids (2 pet, 39) were Aug. . 3.93 ± .74a 3.15 ± .87a Sept.* . 14.84 ± 1.93a 10.93 ± 1.64 b row area interaction. taken most often. Population densities Oct... 3.25 ± .66 b 5.70 ± 1.15a Chrysomelidae (larvae and pupae). remained relatively stable in both fields ^Samples were taken to a depth of 10.2 This group is considered to be (fig. 5) throughout the study, fluctuating cm in soil. Within-row samples were taken ad- phytophagous and contains two between 1 to 11 inseets/6.3 L weekly and jacent to plant stems and included root zone. peaking at 11 ¡nseets/6.3 L on July 2 in Between-row samples were taken midway the control plot. Just as for other groups between the 91-cm rows. =*Mean and standard error of 3 to 5 studied, mechanical cultivation caused ^Growth stages: July (V1-R1); Aug. weekly samples per month. Row means not followed by the same letter are significantly numbers to decrease. Insecticide ap- (R2-R5); Sept. (R5-R6); Oct. (R6-R8). See plication caused no population Literature Cited f7 7;. different (P>0.05). *An asterisk following a month indicates decrease or variation of populations be- significant interaction between field areas tween plots (table 3). We noted a sam- Footnotes continued -^ and row areas within the month. pling area-date interaction for July. This 15 occurred because populations in the Monthly populations remained changes resulted in a highly significant treated field surpassed those ¡n the con- relatively stable in the control for the (P<0.01) sampling area-date interaction trol plots during the last week of July, first 3 months and slightly lower In the for October. whereas those in the control field had treatment plots during that period. No general within-row clustering exceeded the treated plots during the Populations increased 26 to 63 percent tendencies were observed for this group first 4 weeks. Aggregation within rows in all plots from September to October. (table 4). In October, however, high was pronounced for August and Collembola and nematoceran fly im- numbers of larvae were taken within September (table 4). matures also increased during this rows in the control plot, and only a few period. Aggregation of populations Staphylinidae (adults). Rove were collected between rows. In other within rows was found, as for other beetles made up 3 percent (804) of the plots for this month, larvae were evenly groups, in August (table 4). arthropods sampled. Rove beetles are distributed between habitats. This considered to be general predators, and Lepidoptera Oarvae and pupae). phenomenon was reflected in a field some aleocharine species are recorded Tetanolita mynesalis, a saprophagous area-row interaction for October. to be parasitoids that attack dipteran form (24), comprised nearly all of the puparia (2,30). This group became most lepidopterans collected and 2 percent Díptera, Cyclontiapha (larvae and abundant in samples in the latter half of (400) of all arthropods taken in cores. pupae). This group, making up 11 per- the season (fig. 5), following the rainy None of this group was collected until cent (2,939) of all collected specimens, weeks and the buildup of litter after August 6, and none appeared in more was represented in great part by uniden- stage R4. They attained their highest than about 40 percent of the samples tified larvae, probably of several population density of seven beetles/6.3 until August 27, coincidental with heavy families. Anthomyiids, which are L in the control on September 3. Post- leaf drop and the buildup of a leaf-litter primarily saprophagous but which will treatment sampling in August showed a layer in the fields. They reached a consume living plant tissue, also were significant difference between the con- seasonal population peak of three in- identified (25). Population cycles trol and the middle and inner plots in the sects/6.3 L in the control field on resembled those of japygids, with a treated field; parathion treatment September 10 (fig. 5). No effect from in- peak of 27 insects/6.3 L in the control at delayed the population peak by 1 month secticide treatment was present for this midseason and declining precipitously (table 3). The late-season increase in the group (table 3). Populations were by harvest (fig. 5). While no effect from treated field followed 2 months in which relatively stable and similar in both insecticide treatment was detected for populations were significantly lower treated and control plots from August 27 August, it may have occurred in than those in the control. The increase to October 21. We detected a highly September when the control and outer of 66 to 225 percent in the treated plots significant (P<0.01) interaction between plots differed significantly (P< 0.01) from from September to October was coin- sampling areas and weeks for August, the middle and inner plots (table 3). An cidental with a 66-percent decrease in reflecting that larvae were collected overall damping effect on numbers by the control. Poduroid collembolans sporadically in the first 3 weeks of the insecticide treatment was present showed a similar trend of resurgence. August, with no population differences and was overcome during October when The activity of staphylinids, as between plots. During the final week, populations tapered off in both fields. In- measured by pitfalls, also reflected this however, populations were greatest in teraction of the sampling area and population increase because of the the treated plots. Aggregation within dates occurred in July and was highly relatively high number of captures in the rows was observed in the August sam- significant (P < 0.01) in August. This in- treated plots in October. pling for this group (table 4). teraction can be explained by the fact Staphylinids were aggregated Díptera, Nematocera (larvae and that the insects were collected in less within rows during growth stages R2-R6 pupae). Nematoceran fly Immatures than 50 percent of the samples during (table 4). October samples showed a made up 4 percent (1,132) of the the third and fourth weeks of July (about shift to between-row sites. A field area- specimens collected. Most often we en- 58 pet of these were from the control row area interaction was present in countered sciarids that commonly are plot) in contrast to other weeks when 42 September because no populations found in plant detritus and are con- percent of all larvae were concentrated were aggregated within rows in the in- sidered saprophagous (27). They follow- in the outer plot. Populations were even- ner plot during that month. ed a population cycle similar to that of ly distributed among all plots in the first Coleóptera, except Staphylinidae the collembolans, becoming most and fourth August collections; in the (adults). This group made up 4 percent numerous at harvest when leaf litter second week, about 56 percent of the (1,117) of all arthropods collected and was at its maximum for the season. larvae were from the middle plot, and in represents a great variety of beetles Numbers were decreased greatly in both the third week about 50 percent were with diverse habits. Aphodine fields by cultivation on July 9, then built from the control plot. Thus, population scarabaeids (38 pet, 424), anthicids (11 up weekly to a high of 16 insects/6.3 L in surges occurred in the various plots over pet, 123), lathridiids (8 pet, 89), and the treated field on October 21 (fig. 5). the month. ptiliids (8 pet, 89) were taken most often. No effect from insecticide treatment During July and September, \Ne Aphodine scarabaeids are was found in August or September, but, found aggregation within rows to a phytophagous (31), athicids are om- in October, populations of one of the significant degree (table 4). As popula- nivorous feeders (37), and lathridiids (4) treated plots exceeded that of the con- tions decreased for all field areas in Oc- and ptiliids (30) are saprophagous. In trol (table 3). During the first and second tober, they also became more concen- general, weekly populations in the con- week of October, population levels in all trated between rows. This was the only trol approximated those in the treated plots remained similar to September group that was aggregated between field (fig. 5). A high density of six levels. In the final October sample, rows to a measurable degree. Because beetles/6.3 L was reached on July 23 in numbers had more than doubled in all populations began to shift to the the control area. An even distribution of plots, and those of the middle plot between-row sites in the control and populations over all plots and months significantly exceeded those of all the outer plots in September, a highly indicated that the insecticide applica- others, continuing the September pat- significant field area-row area interac- tion did not affect this group (table 3). tern for that plot. These population tion was present for this month. 16 Comparison of Arthropod Popula- Arthropod Population Levels 6.5 Table 6.—Comparison of soil arth- tions at Three Soil Depths. On July 9, Months Following Harvest. We took ropod populations sampled August 5, and September 3, we took core samples to a depth of 10.2 cm in October 21,1974, and May 2, sannples from below the usual depth In the treated plots on May 2,1975,6.5 1975, in an insecticide-treated the control plot to determine which ar- months after the crop was harvested soybean field at McBaine, thopod groups were present. Examina- and the field was planted to wheat and 9 Boone County, Mo. tion of the cores also revealed some months after the insecticide treatment. Arthropod characteristics of the soil structure in Two replications of 10 cores each were group October 21,1974^ May 2,1975' the fields. Those from the top 10.2 cm obtained at three locations, correspond- Poduroid contained large pieces of unincor- ing to the outer-, middle-, and inner- Collem- porated plant debris and were quite treated soybean plots. At the May 2 bola . . ^174.67 ± 23.82a 101.00 ± 20.44 b friable. Cores from the middle 10.2- to sampling, the wheat was about 40 cm Entomo- 20.4-cm depth were packed more dense- high, the soil was damp from recent bryidae 6.75 ± 1.73a 13.67 ± 5.80a ly and contained less observable precipitation and registered a Japy- organic matter. In cores from the lower temperature of 18°C at a depth of 10.2 gidae.. .42± .19a 4.17± 1.95a 20.4 to 30.6 cm, the soil was highly com- cm. No samples were taken in the con- Chry- pacted and had not been disturbed by trol field, which remained fallow follow- some- lidae plowing. ing harvest. We sought to find which (larvae) 0 b .33± .21a Populations of five groups of ar- species were present in the soil after Other thropods were compared for the three crop rotation and whether their popula- Coleóp- depths: Collembolans, japygids, col- tions compared with those in the field at tera eopteran larvae, coleopteran adults, and the last seasonal collection date. (larvae) 4.92 ± .63a 7.67 ± 1.78a nematoceran immatures (table 5). Col- Populations of poduroid Collem- Staphylini- lembola had a vertical distribution of 67 bola were found to be significantly lower dae percent in the upper level, 30 percent in (42 pet, P<0.05) in May than on October (adults) 3.17 ± .60a 4.67 ± 1.45a Other the middle level, and 3 percent in the 21, when they were at their greatest den- Coleóp- sity in the 16 weeks of sampling (table lower level. In the September sample, 50 tera percent of the collembolans were found 6). Lepidopteran larval populations were (adults) 3.00 ± .49a 4.33 ± 2.34a in the upper level, whereas, the July 88 percent lower in May than in October; Lepidop- sample contained 83 percent, and the the difference between the two popula- tera August sample 86 percent. Thus, the tions was significant (P<0.01). (larvae) 1.42± .38a .17± .17 b 10.2-cm depth used throughout our Chrysomelid larvae, not present in Oc- Díptera, study probably sampled the greatest tober samples, were taken in May. Nema- portion of the total collembolan popula- Nematoceran Díptera larvae and pupae tocera tion present in the fields. increased populations by more than (larvae and Japygldae were most numerous in twofold by the May sampling date, and pupae). 15.75± 2.82 b 36.33± 4.25a the lower level for the 3 months, with the difference between dates was highly Díptera, only 26 percent present in the upper significant (P<0.01). Other groups show- Cyclor- level. Only 18 percent inhabited the up- ed no statistically significant difference rhapha per level in July, 55 percent in August, in populations. (larvae and 17 percent in September. Our Collected species included all and estimates of japygid populations in the listed Collembola (except Isotoma viri- pupae). 2.08 ± .54a 5.00 ± 1.86a overall study, therefore, were based on dis and Tomocerus flavescens), chirono- ^Last seasonal collection date before samples from the soil depth containing mid immatures, sciarid immatures, harvest, about 2.5. months after foliar a minor portion of the total population in Pheidole spp., Tetanolita mynesalis, parathion treatment (0.45 kg/ha). 29 months after parathion treatment and the fields. Nadabius ameles, Melanophthalma sp., about 6.5 months after harvest and planting Acratrichis sp., Ptinella sp., Euplectus Coleopteran larvae, coleopteran of wheat. adults, and nematoceran fly larvae all sp., and Rhexius sp. ^Mean and standard error of 12 samples were present in greatest numbers in the (October 21) or 6 samples (May 2). each about upper soil level during the study. 6.3 L of soil. Row means not followed by the Nematoceran lan/ae, however, were not Pitfall-Trapping Study same letter are significantly different present in the upper level sample of July Collembola. Isotoma viridis and (P< 0.05). Student's t-test. 9, and none were collected in the lower Tomocerus flavescens were level. represented equally in pitfalls, jointly nnaking up 15 percent (524) of the 3,524 arthropods trapped. Both are Table 5.—Proportions of soil arthropods at 3 soil depths in untreated soy- saprophagous, and /. viridis is an occa- bean plot at McBaine, Boone County, Mo., 1974 sional predator on snnaller organisms (15). Weekly captures showed con- Arthropod Sample depth siderable variations between weeks and group 0-10.2 cm 10.2-20.4 cm 20.4-30.6 cm fields before and after treatment. On Coliembola ^0.67 ±0.09 ^(5,6,7) 0.30 ±0.09 (1,0.7) 0.03 ±0.03 (0,1,0) July 9 and August 27, cultivation Japygidae .26 ± .03 (10,22,15) .16 ± .03 (13,7,9) .58 ± .04 (33,11,64) resulted in decreased captures in the Coleóptera (lan/ae). .69 ± .09 (4,11,3) .19 ± .08 (2,2.1) .12 ± .06 (1.0.2) control plot (fig. 6). No captures were Coleoptera(adults). .57 ± .13 (3,3,2) .36 ± .13 (3,2.0) .07 ± .07 (0.1.0) recorded on August 6 because of rain- Nematocera (larvae) .63 ± .17 (0,2,3) .38 ± .17 (2,0,1) 0 (0,0,0) fall on that date. Collembolans ap- ^Mean and standard error of 3 samples (5.1 L each). parently were inactive during this rain- ^Numbers collected July 9, August 6, and September 3. respectively. fall period. The most evident differences 17 were between the control and treated TABLE 7.—Mean monthly numbers In the control while decreasing 19 per- fields after treatment. Collembola were of soil arthropods captured In cent in the treated field. The decline in active during August in the control, but pitfall traps in an Insecticide- activity in the treated-plot populations in acltvity was low in the treated field dur- treated and an untreated soy- August was a continuation of the ing this period. bean field at McBaine, Boone decline for those plots beginning in July. Of ail arthropods studied, collem- The treated-field captures becanne County, Mo., 1974 bolans were affected nnost by the insec- significantly higher than those in the ticide treatnnent. July treated-field cap- control, which had decreased from Number of arthropods per pitfall trap in tures did not differ fronn the control Month indicated field August to September. In September, (table 7), but in August, mean dif- Untreated Insecticide captures again were greater in the ferences were significant (P<0.01), and controP treated^ treated field, perhaps because of migra- they remained so throughout Collembola tion from the wheat field as it was September. A field-date interaction was July3 .... 0.41 ± 0.12a^ 0.73 ± 0.22a disked on September 18. Table 8 shows present for August, which indicated that Aug.*^.. 2.25± .58a .20± .02 b that differences between plots were captures were not significantly different Sept 2.20 ± .41a .43 ± .22 b present in July and August, but means Oct 1.22 ± .46a 1.00 ± .43a between fields on August 6 but differed did not differ in September and October Gryllidae significantly in other weeks. By October, July* 45± .14 b 2.10 ± .51a because similar numbers were captured a resurgence In the treated field had Aug 1.18± .30a 1.70± .50a overall areas. Like Collembola, gryllids come about; activity increased there by Sept 79± .19 b 2.20 ± .58a recolonized the treated field to reach 133 percent and decreased by 80 per- Oct 1.44 ± .32a 1.41 ± .23a control-field levels. cent in the control. Coleóptera (larvae) Coleóptera (larvae). This group Within the treated field (table 8), July 76 ± .17a .26 ± .14 b comprised 12 percent (413) of the cap- highest numbers were trapped in the Aug 91 ± .26a .41 ± .12a tured specimens; 57 percent (235) of margins and the outer plots before treat- Sept.* ... 1.58± .24a 1.31 ± .31a these were triungulins of the meloid Oct 38 ± .22a .83 ± .32a ment. After treatment, populations were Carabidae (adults) Epicauta immaculata, which is a reduced in all plots except the margins. July 1.06± .15a 1.91 ± .25a predator of grasshopper eggs (2). The Wheat-field margins reflected distur- Aug 3.83 ± 1.52a 2.04 ± .99 b rest were primarily anthicid larvae, bances from wheat harvest and disking Sept.* ... 1.54± .29a .93± .17 b which are omnivorous feeders (37). We in September, which destroyed the Oct 55 ± .18a .41 ± .09a took the greatest numbers in both fields habitat and caused collembolan activity Staphylinidae (adults) in mid-September. Species of larvae at to cease there during the month. In July 25 ± .05a .23 ± .09a that time were nearly ail meloids, September, the middle-plot captures Aug.* ... .29± .10 b .56± .11a whereas anthicids predominated in July were the same as those from the control Sept 27 ± .09a .45 ± .16a and August. plot, but outer and inner plots registered Oct 08 ± .04a .52 ± .16a Anthicidae (adults) Numbers of larvae trapped in the no captures. Captures evened out over July 1.30 ± .36a .91 ± .22a control exceeded those of the treated all plots, and treated plots recovered to Aug 81 ± .33a .57 ± .14a plots on each date until Septembers, control field levels as the effects of the Sept 14 ± .08a .12 ± .04a but significant differences between con- insecticide treatment were overcome in Oct 02 ± .02a .05 ± .05a trol and treated fields were found only in October. Road margin captures were Other Coleóptera (adults) July (table 7), indicating no treatment ef- higher than those of other areas in July 36 ± .07 b .80 ± .16a fect. A field-date interaction was present August, September, and October, Aug 60 ± .20a .43 ± .12a in September, which showed that a possibly because this area was not Sept 33 ± .09a .25 ± .05a significant (P<0.05) difference between Oct 16 ± .08a .08 ± .04a weeded. Formicldae field means was present only on the July 91 ± .26a .25 ± .06a September 24 sampling date. Anthicids Gryllidae. This group comprised Aug 66 ± .22a .16 ± .08a also were taken in core samples, but no Gryllus spp. and Allonemobius Sept 1.51 ± .47a .47 ± .17a treatment effect was found for col- fasciatus, which were sampled in even Oct 55 ± .17a .27 ± .16a eopteran larvae from those samples. proportions. They made up 18 percent of Lycosidae Activity varied across the treated the pitfall captured arthropods. Both are July 16 ± .04a .60 ± .17a plots in August; the greatest number of known to be omnivorous feeders (14). Aug 31 ± .10a .08 ± .04a captures was in the wheat field miargin Sept 25 ± .10a .14 ± .05a Numbers captured were highest in the (table 8). As for gryllids, no difference in treated field during July (fig. 6) but were Oct 08 ± .05a .05 ± .03a Other Araneae captures between plots was found in lower than the control on August 6 after September and October. treatment. In following weeks, however, July 16 ± .04a .15 ± .04a Aug 12± .06a .10± .04a most insects were taken in the treated Sept 18± .06a .16± .06a Carabidae (adults). Carabids made field until October 16. Cultivation coin- Oct 36 ± .08a 0 b up 22 percent (766) of the trapped arth- cided with fewer captured arthropods on ^Control plot located about 250 m from ropods. There were 35 species, notably September 3. insecticide-treated field. Bembidion rapidum (36 pet, 276), Tachys We found no clear effect of treat- ^Parathion applied at 0.45 kg/ha by anceps (11 pet, 84), Harpalus pennsyl- ment for this group. Comparison of airplane on August 2,1974 (R2). vanicus (9 pet, 71), H. testaceus (7 pet, monthly means (table 7) revealed ^»Growth stages: July (V1-R1); Aug. 54), Pterostichus chalcites (7 pet, 52), significantly higher numbers in the (R2-R5); Sept. (R5-R6); Oct. (R6-R8). See Cratacanthus dubius (5 pet, 38), H. treated field in July with an interaction Literature Cited C77;. caliginosus (4 pet, 31), and Microlestes between weeks and fields, indicating ^Mean and standard error of twelve 24-h samples taken weekly in each field. Row spp. (3 pet, 23). Acupa/pus, Agonoderus, that catch differences between fields means not followed by the same letter are Agonum, Amara, Anisodactylus, Bem- were not significant for July 2,16, and significantly different (P<0.05). bidion, Calosoma, Cfilaenius, Clivina, 30. No difference in capture means was ^An asterisk following a month indicates Harpalus, Patrobus, Pterostichus, found for August, but the catch in- significant interaction between fields and Scarites spp., Agonum placidum, and H. creased 260 percent from July to August weeks within months. caliginosus have been recorded as her- 18 _Q ^ X) n ^ X3Xi Xi ^ Xi Xi bivores (18). Agonoderus, Agonum, CO CO CO ÇO co co co co 1- o> mbers of s( jnty, Mo., 1! 1. 1885Í8 SS8K 5§ss?? 5S^5?? 5 8 cô 5 5 in >» ^ co .9 October, activity decreased in all plots, 3 o cvir^coi^ T— T-: co • " (/> ' ' ' ' ü ü Ü except for the margin areas. 5 Xi n co co co ¿ 0)>c^ co I"! CO CO Pïsa iÂ^Â Staphylinidae (adults). This group S ö ^^11 made up 5 percent (166) of the arth- +1 +1 +1 +1 +1 +1 +1 +1 +1 +1 +1 +1 +1 +1 +1 +1 +1 +1 ropods captured in pitfalls. Numbers montl ), BOG 8 s ss^^ sss^ S S o S !5S3^ g "co >*"g © 1-^ o o T-: t— T— Csi 1-^ ^ captured in the treated field actually cl were greater than those from the control ^n n n Xi Xi JD Xi E SS cO cO cO ^ Q-S co ÎO in 10 of the 11 weeks following treat- So lô t-^ ment (fig. 6). 1 s 2^ Ö 1 ^ ^8 +1 +1 +1 +1 +1 +1 -H +1 +t +1 +1 +1 +1 +1 +1 +1 +1 +1 +1 +1 "ÖZ£ ^tl In July, before treatment, no dif- «■ö 3 " ^8881 i§f:;f?5 fssss 8SS18 ^afqS ference in captures between fields was LU o Ö CNJ Csi T- t— 1— ^~ 1-: co T^ present (table 7). Captures in August flÛ c were higher for the treated field, o iiii ¿Hi ^ ^ (D o îli§ O representing a 143-percent increase in 19 number of anthicids was captured in July (fig. 6), corresponding to peak populations of coleopteran larvae in cores, of which anthicids made up about 1 percent. The lowest number of captures occurred in October. They were not affected by treatment because no difference between field means was observed for the posttreatment months, (table 7). The decrease in activity from July to August was 38 percent for both the control and the treated field. Greatest numbers in an individual plot were from the wheat field margin In September and October (table 8). Staphylinids, ants, carabids, col- eopteran larvae and adults, and gryllids also were most active in the wheat border in October. We found no other significant difference among plots. Other Coleóptera (adults). This group made up 5 percent (185) of the pit- fall captures. Beetles most often taken were Negastrius pectoralis (53 pet, 98), an herbivore (24). Aphodius prodromus and Ataenius spp. (20 pet, 37) in even proportions, and Melanophthalma sp. (9 pet, 17). This group was affected markedly by treatment (table 7) because captures increased by 67 percent from July to August in the control and dropped by 46 percent in the treated field. Both fields decreased in activity at a similar rate for the balance of the season (fig. 6). Before treatment, we caught the most beetles in the outer plot. Differences between plots were leveled out by treatment, but all plots within the treated field showed a decrease in captures, compared with an increase in the control. Activity was I I I I I' Í I I III sustained in the wheat field margin in July Aug Sept October (table 8) while captures fell off FIGURE 6.—Seasonal pitfall captures of soil arthropods in insecticide-treated in other areas. and untreated soybean fields, McBaine, Boone County, Mo. Vertical-dashed line indicates parathion application on August 2,1974. Formlcidae. Ants made up 10 per- cent (345) of the captures during the study and were represented primarily by Pheidole spp., Lasius neoniger, and activity fronn July in contrast to only a highest catches were in September, but Hypoponera opacior'm decreasing order 16-percent increase in the control. A no significant difference was found in of abundance. Of these, Pheidole spp. date-field interaction was present for October. and H. opacior are predaceous (39). L August because control field captures Several of the staphylinid species neoniger is a root-aphid tender and were higher than those of the treated sampled in pitfalls also were taken in predator f3ô;. field for August 20. Activity in the cores. Gore samples showed a Ants maintained their highest ac- treated field remained relatively un- 66-percent decrease in populations from tivity levels in September, a period of changed for the rest of the study but September to October in the control relatively dry conditions, following a decreased by 72 percent by October in coupled with a 66- to 225-percent in- week of heavy rain (table 2). Activity did the control plots. crease in the treated plots. This popula- not seem to abate by harvest (fig. 6). In- Before treatment, significantly tion difference between fields was secticide treatment had no significant higher captures came from the outer linked to the sharp decrease in activity effect on ant activity (table 7) because plot (table 8). After treatment, in the control plots and slight increase numbers captured were highest for all staphylinids increased activity in ail of the treated plots during that period. sampling weeks in the control. In the treated plots, as well as the control, with Anthicidae (adults). Anthicids con- treated field, activity was most pro- significantly higher captures in the inner stituted 8 percent (277) of the total pitfall nounced in the field margins in all plot, which showed an increase in activi- catch. Anthicus cervinus (50 pet, 139) months (table 8). Significant differences ty of fifteenfold from July to August. The was trapped most often, followed by >!\. between the control and treated plots wheat field margin showed that the ephippium (20 pet, 55). The largest were found in July before insecticide 20 season, perhaps exploiting the increas- treatment. Most ants were trapped in Discussion ing collembolan population as a food the middle plot in September. The present study added 162 Araneae, Lycosidae. This predace- species to the list of 589 arthropod source. ous group (19) constituted 3 percent species known from soybean fields in Pitfall-sampling data indicated that (125) of the pitfall captures; Pardosa Missouri (3). The only other comprehen- all groups, except collembolans, were milvina and P. saxátil is, in even propor- sive study of soil arthropods of soybean present in all plots of the treated field tions, made up 90 percent (113) of the fields was conducted in Iowa where 208 during the week following the insec- specimens. genera were recorded (22). In the Iowa ticide treatment. This indicated either study, samples were taken to a depth of that no arthropods were decimated ini- Greatest wolf spider activity (fig. 6) 6.0 cm, and Tullgren funnels were used tially by the treatment or that field occurred in the treated field in July, to extract arthropods from the cores. recolonization occurred within 4 days of when hot dry weather and sparse Although different sampling methods treatment before the first posttreatment ground cover prevailed. In July, weekly were used for the Iowa and Missouri sampling. Therefore, we noted no captures were twice as great in the studies, 18 genera were common to soy- gradual migration from outer- to inner- treated field as in the control, but after bean fields in both States. Those arth- field areas. No collembolans were col- treatment this trend was reversed. In ropods collected in large numbers in lected in the treated field traps for 3 August, captures increased 94 percent both studies were Onychiurus sp., weeks following the insecticide applica- in the control and decreased 87 percent Folsomia sp., Proisotoma sp., En- tion. Core-sampling data also revealed in the treated field, but no treatment ef- tomobrya sp., Pseudosinella sp., that all arthropod groups were present fect was noted when monthly means Japygidae, Ptinella sp., Anthicidae lar- in the three treated plots within 4 days were tested because too few spiders vae, and Ceratoma trifurcata larvae. after treatment. were sampled (table 7). Activity then Mites made up about 25 percent of the All arthropod groups sampled in decreased by 20 percent from August to genera recorded and were the most cores, except fly immatures, were ag- September, but a 75-percent increase numerous arthropods collected in the gregated within the plant rows during was detected in the treated field. By Oc- Iowa study. August. The habitat was disturbed least tober, differences between fields, as Soil cores differed from pitfall traps by mechanical weeding in August, con- reflected in monthly means and weekly in the kind of information gathered tained the roots of the soybeans, and captures, indicated that effects of treat- about arthropod populations. Those ar- accumulated a leaf-litter layer by mid- ment had been overcome. thropod species that live far below the August. Predators such as japygids and After treatment in August, greatest soil surface and do not move about ex- staphylinids probably aggregated in decreases in numbers trapped were tensively on the surface were sampled close association with their collembolan found in the middle and inner plots exclusively in cores. Pitfalls captured prey. Entomobryid collembolans and (table 8). Spiders again were taken in the only arthropods that moved about on cyclorrhaphan fly immatures also were inner area in September, and activity the soil surface and, with the exception aggregated within rows in July because levels were similar in all areas during of the staphylinid beetles, populations of oviposition around the young plants that month. No spiders were captured in of these species were too low to be by the adults. A previous study showed the middle-, inner-, or wheat-margin measured by core sampling. Thus, the that more than 90 percent of bean leaf plots in October while significantly sampling methods complemented each beetle eggs are laid within a soil area 7.6 (P<0.05) highest numbers were taken in other in providing information on the cm from the soybean stems and 3.8 cm the road margin. species composition of the soil fauna in depth (36). The southern corn root- Araneae, other families. All and the effect of the insecticide treat- worm deposits its eggs in a similar prox- members of this group are considered ment on their populations. imity to the stems (16). The ovipositional to be predaceous (19). They made up 2 On the date of the insecticide treat- behavior of these two species may ex- percent (89) of the pitfall catch; Erigone ment, the leaf canopy was almost clos- plain the significant (P<0.01) degree of autumnal is was the most abundant. ed, and weeds formed a moderately aggregation of chrysomelid immatures Gnaphosids made up a large part of the heavy ground cover. Under these condi- within rows in August and September. tions, we expected only a small amount rest of the specimens. The 10.2-cm core-sampling depth The peak of activity for this group of the insecticide spray to reach the soil probably included the strata containing was reached in the control in October surface, but rain (0.2 cm) and dew prob- the greatest portion of the populations (fig. 6). We found no effect from insec- ably contributed to the leaching of residues into the soil on the day of ap- of collembolans, coleopteran larvae and ticide treatment. Numbers captured adults, and nematoceran fly larvae in were significantly greater in the control plication. In this manner, soil arthropods possibly were exposed to the parathion the field over the season, but many ar- and increased in October while the thropods were sampled to the 30.6-cm treated field registered no captures for directly. Direct mortality of adult chrysomelid beetles and flies on the depth. In grassland ecosystems, more the month (table 7). than 89 percent of the collembolan Spiders were distributed evenly foliage could have decreased egg deposition in the soil, which contributed population occurs in the upper 7.6-cm across the control and treated fields in horizon of samples taken to a depth of July, August, and September (table 8). We to decreased larval populations of these 22.8 cm (10). Grassland presents an en- trapped the most spiders in the wheat arthropods after treatment. vironment undisturbed at the soil sur- field margin in July and August. No Populations of poduroid collem- face by plowing, in contrast to the soy- spiders were trapped in the outer-, inner-, bolans in the treated field were higher bean field, which was disturbed by or wheat-margin plots in October, but than those in the untreated field by mechanical weeding twice during the numbers captured actually increased harvesttime. The decrease in numbers growing season. from September to October in the control of japygids (collembolan predators), and road margin. This was not due to an following treatment, may have con- Another study demonstrated that effect that occurred 2 months after treat- tributed to this resurgence. Staphylinid many species of arthropods found in ment but rather to spider populations beetles also reached a population peak agricultural soils in California inhabit that were too low to sample effectively. in the treated field at the end of the depths below 46.0 cm (28). In this study, 21 64 percent of ail arthropods were found (2) in the upper 15.2 cnn of cores taken to a Surges and F. Raw, eds., Soil 1935. The bionomics of entomo- Biology. Academic Press, New depth of 30.5 cm. Japygid diplurans phagous Coleóptera. J. Swift Co., York. were nnore numerous in samples from New York. 220 p. (16) Isley, D. the 20.4- to 30.6-cm depth than at other (3) Blickenstaff, C. C, and J. L Huggans. 1929. The southern corn rootworm. depths in our study. Surveys for japygids 1962. Soybean insects and related Arkansas Agricultural Experiment might have provided more information if arthropods in Missouri. Missouri Station Bulletin No. 232,31 p. soil samples had been taken to a depth Agricultural Experimentstation (17) Research Bulletin 803.51 p. 1930. The biology of the bean leaf- of more than 10.2 cm. (4) Borror, D. J., and D. M. Delong. Vertical distribution of populations beetle. Arkansas Agricultural Ex- 1971. An introduction to the study of periment Station Bulletin No. 248 changed between the three sampling insects. Holt, Rhinehart, and 20 p. dates for each arthropod group. Vertical Winston, New York. 812 p. (18) Johnson, N. E., nd R. S. Cameron. movement in the soil is well (5) Burgess, A. F., and C. W. Collins. 1969. Phytophagous ground beetles. documented for collembolans (35) ano 1917. The genus Calosoma in- Annals of the Entomological Soci- wireworms f72;and occurs mainly in cluding studies of seasonal histories, ety of America 62:909-14. response to temperature changes on a habits, and economic importance of (19) Kaston, B. J. seasonal basis. No studies have shown American species north of Mexico 1948. Spiders of Connecticut. and of several introduced species. how often populations of diverse groups Connecticut State Geological and U.S. Department of Agriculture Natural History Survey Bulletin No. migrate vertically in the soil, and it is dif- BulletinNo. 417.124p. ficult to speculate whether the weekly 70,874 p. (6) earner, G. R., M. Shepard, and S. G. (20) Kretzschmar, G. P. population fluctuations we observed in Turnipseed 1948. Soybean insects in Minnesota the 0- to 10.2-cm depth were in response 1974. Seasonal abundance of insect with special reference to sampling to vertical migration or to other factors pests in soybeans. Journal of technique. Journal of Economic such as natality or mortality. Economic Entomology 67:487-93. Entomology 41:586-91. Mechanical cultivation caused (7) Christiansen, K. (21) Kuhnelt, W. decreased pitfall captures of collem- 1964. Bionomics of Collembola. 1961. Soil biology. Faberand Annual Review of Entomology bolans, gryllid crickets, staphylinid Faber, London. 397. p. 9:147-78. (22) Loureiro, M. C. beetles, coleopteran larvae, and carabid (8) Coaker, TH., and D.A.Williams. beetles. In the wheat field margin and 1976. Synecology of edaphic arthro- 1963. The importance of some Car- poda in Iowa agroecosystems. Ph. the road margin, where cultivation did abidae and Staphylinidae as D. thesis, Iowa State University, not take place, captures of collem- predators of the cabbage root fly, Ames. 130. p. bolans, anthicid beetles, and ants were Erioischia brassicae (Bouche). (23) Marston, N. L, and M. K. Hennessey. higher than in other areas in September Entomología Experiamentalis et 1978. Extracting arthropods from and October. These areas were weedy, Applicata 6:156-64. plant debris with xylene. Journal of and the wheat field margin probably (9) Deitz, L L, J. W. Van Duyn, J. R. the Kansas Entomological Society captured insects migrating from the Bradley, Jr., and others. 51(2):239-44. 1976. A guide to the identification (24) Metcalf, C. L, W. P. Flint, and R. L wheat field after it was disked in late and biology of soybean arthropods September. Metcalf. in North Carolina. North Carolina 1962. Destructive and useful insects. Several species show promise as Agricultural Experimentstation McGraw-Hill Co., New York. 1,087 p. subjects for future research on the en- Technical Bulletin No. 238,264 p. (25) Miller, L A., and R. J. McClanahan. vironmental impact of foliar pesticides (10) Dhillon, B. S., and N. H. E. Gibson. 1960. Life hstory of the seed-corn on the soil arthropod community. 1962. A study of the Acariña and maggot, Hylemya cilicrura (Rond.), Tomocerus flavescens and Isotoma Collembola of Agricultural soils. I. and of H. liturata (Mg.) (Diptera: An- viridis proved highly sensitive to Numbers and distribution in un- thomyiidae) in southwestern On- disturbed grassland. Pedobiologia tario. Canadian Entomologist parathion and were captured readily in 1:189-209. pitfall traps, which are a relatively sim- 112:210-21. (11) Fehr, W. R., C. E. Caviness, D. T Burmood, (26) Milliron, H. E. ple sampling method. Subterranean ar- and others. 1958. Economic insect and allied thropods, such as Folsomia hoff i and 1971. Stage of development descrip- pests of Delaware. Delaware diplurans, affected directly by parathion tions for soybeans, Glycine max (L) Agricultural Experimentstation application, were abundant in sufficient Merrill. Crop Science 11:929-31 Bulletin No. 321,87 p. amounts to provide population (12) Fisher, J. R. (27) Oldroyd, H. estimates based on our core sample 1973. Seasonal vertical distribution 1964. The natural history of flies. size, and may be collected in smaller and biological observations on W. Clowes and Sons, Ltd, London sample sizes to facilitate extraction. three genera of wireworms affect- 324 p. ing corn in central Missouri. M.S. Collembolans also are efficiently ex- (28) Price, D. W., and G. S. Benham, Jr. thesis, University of Missouri, 1977. Vertical distribution of soil- tracted for counting with the xylene Columbia. 96 p. inhabiting microarthropods in an method. Standardized methods for (13) Fox, C. J. S., and C. R. MacLellan. agricultural habitat in 1956. Some Carabidae and Staphyl- assessing the impact of pesticides us- California. Environmental En- ing one or more of these organisms inidae shown to feed on a tomology 6(4):575-80. could be developed based on the wireworm, Agriotes sputator (L.\ by (29) Radcliffe, R. H., T L BIssell, and methods used in this study. the precipitin test. Canadian En- W. E. Bickley. tomologist 88:228-31. (14) Gangwere, S. K. 1960. Observations on soybean in- sects in Maryland. Journal of 1961. A monograph of food selec- Economic Entomology 53:131-33. Literature Cited tion in Orthoptera. Transactions (30) Raw, F. of the American Entomological (1) Baiduf.W.V. 1967. Arthropoda (except Acari and 1923. The insects of the soybean ¡n Society 87:67-230. (15) Hale,W.G. Collembola), p. 323-62. In A. Surges Ohio. Ohio Agricultural Experi- and F. Raw, eds., Soil Biology. 1967. Collembola, p. 397-411./A? A. ment Station Bulletin 466:145-81. Academic Press, New York. 22 (31) Pitcher, P. O. of the total number extracted from the variability in extraction efficiency be- 1958. Biology of Scarabaeidae. samples was in the third wash. Collem- tween weeks and between field- Annual Review of Entomology bolans and japygids were extracted in sampling areas. The second and third 3:311-34. similar proportions in successive washes added about 20 min to the total (32) Salt, G., and F. S. J. Hollick. time spent processing a soil sample. 1944. Studies of wireworm popula- washes, as were coleopteran and tions. I. A census of wirewornns in dipteran larvae. They were justified, however, because pasture. Annals of Applied The flotation technique probably the number of arthropods extracted in Biology 31:53-64. did not remove 100 percent of any of the the second and third accounted for (33) F. S. J. Hollick, F. Raw, and arthropod groups from soil samples. about 31 percent (91) and 16 percent (47), M. V. Brian. Wetness of soil samples when taken in respectively, of the total arthropods ex- 1948. The arthropod population of the field and amount of leaves and roots tracted in our tests. pasture soil. Journal of Animal present may have contributed to Ecology 17:139-50. (34) Tugwell, P., E. P. Rouse, and R. G. Thompson. Table 9.—Effectiveness of successive saturated saltwater washes in 1973. Insects in soybeans and a extracting arthropods from soil samples weed host {Desmodium sp.). Arkansas Agricultural Experiment Arthropod Proportion of total arthropods extracted in indicated wash Station Report Series No. 214, group 18 p. Collembola ^0.50 ±0.06 2(5,23,3) 0,34 ±0.06 (2,18,1) 0.16 ±0.05 (2,8,0) (35) Usher, M. B. Japygidae .47 ± .04 (52,3,20) .33 ± .04 (33,1,19) .20 ± .03 (27,1,4) 1970. Seasonal and vertical distri- Coleoptera(larvae). .66 ± .08 (14,5,4) .26 ± .07 (4,1,4) .08 ± .05 (0,0,3) bution of a population of soil ar- Coleoptera(adults). 1.00±0 (2,1,1) 0 0 thropods:Collembola. Pedobi- Diptera(lan^ae) .60 ± .10 (12,0,3) .32 ± .09 (8,0,0) .08 ± .05 (2,0,0) ologia 10:224-36. (36) Waldbauer, G. P., and M. Kogan. ^Mean for 3 replications. Standard error determined by normal approximation. ^Numbers of arthropods collected from a sample (6.3 L) located within row (August 20), 1975. Position of bean leaf beetle eggs in soil near soybeans deter- between row (July 9), and between row (August 20), respectively. mined by a refined sampling pro- cedure. Environmental En- Appendix 2 binocular microscope to determine the tomology 4(3):375-80. percentage of each arthropod group ex- (37) Werner, F. G. Experinnents with the xylene ex- 1964. A revision of the North Ameri- traction technique revealed that, in tracted by the xylene. can species of Anthicus, s. str. general, small aliquots of sannples are Among the five groups tested, we (Coleoptera:Anthicidae). En- extracted more efficiently than large obtained the best extraction for collem- tomological Society of America ones, but a greater number of aliquots bolans and the poorest for dipteran im- Miscellaneous Publication increase labor and time; therefore a matures (table 10). The rather large 4:194-242. balance was struck between three percentages appearing under the "Hand (38) Wheeler, G. 0., and J. Wheeler. parameters. We used samples of about sorting" column indicate that the xylene 1963. The Ants of North Dakota. 100 ml of organic debris as slurry from procedure is ineffective for estimating University of North Dakota Press, absolute populations of all arthropods Grand Forks. 326 p. the 100-mesh sieve and extracted them (39) Whitcomb, W. H., H. A. Danmark, in 10-ml aliquots in 950-ml lidded in soil organic debris unless hand sort- A. P. Bhatkar, and others. polyethylene cups. About 50 ml of ing is included as a final step or unless 1972. Preliminary studies on the xylene provided a dd-cm^ interface area the data are adjusted to account for the ants of Florida soybean fields. between the slurry and xylene. From percentage of loss (which will vary with Florida Entomologist 55:129-42. tests of several cup sizes and shapes, the arthropod group being extracted). In (40) Wyman, J. A. we found that increasing the our study, the technique saved con- 1974. Corn seed beetles as cab- xylene/water interface area enhanced siderable hand sorting labor since col- bage maggot egg predators. Pro- efficiency of extraction because ar- lembolans were extracted very well. ceedings of the North Central They made up about 37 percent of the Branch, Entomological Society of thropods aggregated at the interface. America 29:172. In six test replications, we proc- arthropods, other than mites, in the essed each sample twice with xylene average sample. and then hand sorted them under the Appendix 1 The saltwater flotation technique varied in its efficiency for extracting five Table 10. —Effectiveness of xylene extraction in separating arthropods groups of arthropods (table 9) from soil. from organic debris from soil samples^ In our trials, the effectiveness of the Arthropod Percent total arthropods extracted in indicated step technique increased as the proportion group Xylene 1 Xylene 2 . Xylene 1 + 2 Hand sorting of the arthropod group recovered in the first wash increased. Generally, the first Collembola =^61.5± 11.7 37.7± 11.2 99.2 0.8± 0.7 wash extracted the greatest nunnber of Coleóptera(lan/aeand pupae) . . . 54.5 ± 29.1 13.5 ± 18.0 68.0 32.0 ± 26.5 Coleoptera(adults) 57.0 ± 34.0 24.9 ± 14.3 87.3 12.7 ± 14.4 arthropods in each replication, and the Diptera(lan/aeandpupae) 4.5± 6.2 11.7± 7.7 16.2 83.8±11.0 nunnber of arthropods extracted from Otherarthropods^ 62.9 ± 14.6 28.9 ± 12.1 91.8 8.2 ± 9.9 the samples decreased with successive ^Sample size was 50 ml with 95-cm2 water-xylene interface area. washings. We obtained the best extrac- ^Mean and 95 percent confidence inten/al. tion efficiency for coleopteran adults ^Lepidoptera, Hymenoptera, Diplopoda, Araneae. because none were found in the second or third washes for any of the replica- tions. Poorest extraction efficiency was found for the Japygidae, as 20 percent Si-Ü . s . Covernm n!: Printing Office 381-227/2053 23 United States Department of Agriculture Agricultural Research Service Washington, D.C. 20250 OFFICIAL BUSINESS P«naitv for Private Use, $300 Postage and Fees Paid United States Department of Agriculture AGR-101 Ö (larvae) --10M cided with establishment of a leaf-litter "O layer after soybeans reached R6, the I 10- green bean stage, reaching 175 adults o :trÄ=>fe:»<5::yg»^«gfeg and immatures/6.3 L in the treated field <50 fl'üAíM&rSSM on October 21. A good recovery of Nematocera ( larvae & pupae) poduroid collembolans was evident in 40 the treated field as they increased to a level 1.8 times the control by October 21. 30 When we analyzed monthly data (table 3), we detected an interaction be- 20 tween field areas and sampling dates ■A/ ^ for July t)efore treatment. Populations 10 . /-J : Cyclorrhapha on July 2 and 23 were low, and dif- (la rvae& pupae) ferences between plots were small. 30- Populations of middle and inner plots Chrysomelidae (larvae) were lower than control and outer plots 20- for all sampling dates, except for July 16 when collections in the inner plot 10 10 equaled those of the control and the outer plots. While control populations I i"y"'ry f"T I I i i i i i ii increased 11 percent from July to July July Aug Sept Oct August, populations decreased during FIGURE 5.—Seasonal soil arthropod populations per 6.3 L of soil (10.2-cm this period in the treated field, resulting depth) in insecticide-treated and untreated soybean fields, McBaine, Boone in a highly significant difference County, Mo. Vertical-dashed line indicates parathion application on August 2, (P-0.01) between the control and all 1974.