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Document Type

Peer-Review Article

Abstract

A rich fauna of coccinellids occurs in eastern South Dakota, but the abundance of some species has declined in association with the establishment of an exotic lady beetle, Coccinella septempunctata (L.) (Coleoptera: Coccinellidae), in the mid-1980s. In this study, coccinellids were sampled within field-crop and grass habitats in eastern South Dakota from 1990 to 1995 to survey for various coccinellid species and to determine any effects of habitat management on abundance. Field crops (maize, wheat-alfalfa intercrop, and alfalfa) were subjected to high, intermediate, or low crop-management intensity (CMI), and grass habitats were managed for stands of warm season, cool season, or mixed species. A total of 1,306 adult and 155 larval coccinellids were collected. Four native species (Coleomegilla maculate (DeGeer), Hippodamia convergens Guerin Meneville, Hippodamia parenthesis (Say), andHippodamia tredecimpunctata tibialis (Say)) and C. septempunctata comprised over 96 percent of all coccinellids collected. Of declining species, four Coccinella transversoguttata richardsoni Brown were collected from alfalfa, but Coccinella novemnotata Herbst and Adalia bipunctata (L.) were not found during the study. Coccinellid abundance was seldom affected by CMI. Coccinellids were more abundant in wheat-alfalfa in 1995 under high than low CMI. Coccinellid abundance in maize and alfalfa did not differ with CMI. A prey species, Empoasca fabae (Harris) (Heteroptera: Auchenorryncha: Cicadellidae), was more abundant in alfalfa in 1995 under high and intermediate than under low CMI. Coccinellid abundance was not correlated with that of E. fabae in 1995, and showed inconsistent association with E. fabae during the study. In grass, adult coccinellids (total across species), adult H. tredecimpunctata tibialis, and aphids were more abundant in warm- season grasses than in cool-season or mixed grass stands in one of three years. Our results provide further evidence that C. septempunctata has become relatively abundant in eastern South Dakota, whereas C. transversoguttata richardsoni, C. novemnotata, and A. bipunctata have become rare or absent.

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