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Species composition and relative abundance of Coccinellidae (Coleoptera) in South Central Nebraska field crops.

2000; Kansas (Central States) Entomological Society; Volume: 73; Issue: 2 Linguagem: Inglês

1937-2353

Robert Wright, Thomas A. de Vries,

Biological Control of Invasive Species

Species composition and relative abundance of adult Coccinellidae were mon itored in field corn {Zea mays L.), grain sorghum {Sorghum bicolor L. Moench.), winter wheat {Triticum aestivum L.) and alfalfa {Medicago sativa L.) in south central Nebraska during 1992-1995. Two native coccinellids, Hippodamia convergens Guerin-Meneville and Coleomegilla maculata (DeGeer), were the most common species during all years and in all crops, comprising >77% of the individuals observed. Averaged over all years, H. convergens was the most common species in alfalfa and sorghum, and C. maculata was the most com mon species in corn and wheat. Other species collected included Coccinella septempunctata (L.), Hippodamia parenthesis (Say), Hippodamia tredecimpunctata tibialis (Say) and Cy cloneda munda (Say). Although there was variation in species composition by crop and year there were no significant differences in species diversity as measured by the Berger-Parker species dominance index (d) and the Shannon-Weaver function (H). This information will help target future studies in conservation, augmentation and classical biological control in volving coccinellids. Lady beetles (Coccinellidae) are important components of biological control in many crops (Obrycki and Kring, 1998). Knowledge of the species present, their abun dance and seasonal occurrence is important to understand how to encourage coc cinellid activity through conservation and augmentation. This information is also im portant to provide a baseline for future studies evaluating the impact of classical biological control on native coccinellids (e.g., Elliot et al., 1996; Obrycki et al., 2000). Previous studies in other Midwestern U.S. states have examined species diversity and relative abundance of coccinellids on field crops in South Dakota (Elliot and Kieckhefer, 1990a, b; Kieckhefer and Elliot, 1990; Kieckhefer et al., 1992), Min nesota (Ewart and Chiang, 1966), Iowa (Giles et al., 1994), Kansas (Rice and Wilde, 1988, 1991), and Missouri (Richerson and DeLoach, 1973). We are not aware of any similar studies in Nebraska field crops. These studies were conducted during 1992-1995 to document the species com position and relative abundance of coccinellids on field corn {Zea mays L.), grain sorghum {Sorghum bicolor L. Moench.), winter wheat {Triticum aestivum L.) and al falfa {Medicago sativa L.) in south central Nebraska. Methods and Materials During 1992-95 field corn, grain sorghum, winter wheat, and alfalfa fields were sampled for adult Coccinellidae at the University of Nebraska's South Central Re search and Extension Center farm located in Clay County, Nebraska (40?3rN, 98?02'W). Although soybeans, Glycine max (L.) Merrill, are an important field crop in this area, preliminary observations indicated low arthropod abundance in soy beans, and no lady beetle collections were made in this crop. With the exception of granular soil insecticides applied at planting for corn rootworm control in corn, no insecticides were applied to the fields sampled. Samples were collected at intervals >2 weeks periodically throughout the grow ing season. A sample consisted of a collection from one field of a particular crop. A This content downloaded from 157.55.39.78 on Sun, 19 Jun 2016 07:09:41 UTC All use subject to http://about.jstor.org/terms 104 JOURNAL OF THE KANSAS ENTOMOLOGICAL SOCIETY Table 1. Relative abundance of lady beetle species by crop and year, Clay Center, NE. % of totals Lady beetle species 1992 1993 1994 1995 Avg Alfalfa C. septempunctata 5.56 38.18 9.56 15.38 17.17 C. maculata 8.33 10.91 21.32 50.00 22.64 C.munda 2.78 1.82 0.00 0.00 1.15 H. convergens 80.56 38.18 64.71 34.62 54.51 H. parenthesis 2.78 10.91 2.21 0.00 3.97 H. tredecimpunctata tibialis 0.00 0.00 2.21 0.00 0.55 Corn C. septempunctata 1.61 5.00 ? ? 3.31 C. maculata 54.84 77.0 ? ? 65.92 C.munda 3.23 0.00 ? ? 1.62 H. convergens 37.10 18.00 ? ? 27.55 H. tredecimpunctata tibialis 3.23 0.00 ? ? 1.62 Sorghum C. septempunctata 9.03 6.49 0.00 ? 5.18 C. maculata 22.58 4.55 43.33 ? 23.49 C.munda 1.29 0.00 0.00 ? 0.43 H. convergens 61.29 85.06 50.00 ? 65.45 H. parenthesis 0.00 0.65 1.67 ? 0.77 H. tredecimpunctata tibialis 5.81 3.25 5.00 ? 4.68 Wheat C. septempunctata ? 4.82 1.05 0.00 1.96 C. maculata ? 44.58 26.32 64.94 45.28 C.munda ? 4.82 0.00 1.30 2.04 H. convergens ? 27.71 52.63 16.88 32.41 H. parenthesis ? 12.05 5.26 1.30 6.20 H. tredecimpunctata tibialis ? 6.02 14.74 15.58 12.12 standard 76 cm sweep net was used to sample lady beetles in alfalfa and winter wheat. Sample size ranged from 100-300 180? sweeps depending on the abundance of lady beetles present. Visual examination of plants was used to sample lady bee tles in field corn and grain sorghum. Sample size consisted of a single row, ranging in length from 30-90 m depending on the abundance of lady beetles present. Sam ple sizes were increased if initial sampling did not collect at least 10 lady beetles. Previous research shows that the sweep net and visual examination methods repre sent unbiased sampling methods for estimating the relative abundance of coccinel lids on these crops (Kieckhefer et al., 1992; Michels and Behle, 1992). No attempt was made to collect larvae, or smaller coccinellids such as Scymnus or Stethorus spp. Samples were pooled by crop on each date, and stored in 70% ethanol. Species were identified using characteristics described by Gordon (1985). Species diversity by crop and year were characterized using the Berger-Parker species dominance index (d) and the Shannon-Weaver function (H) (Southwood, 1978). Differences in species diversity among crops and years were analyzed by ANOVA (PROC GLM, SAS, 1985).