INTERACTIVE EFFECTS OF SOIL-APPLIED PESTICIDES, CULTIVAR, AND PLANTING DATE ON THE SOYBEAN-INSECT COMPLEX IN NORTH CAROLINA.

摘要

This investigation was conducted in North Carolina from 1978 to 1980 to obtain information leading to the management of Heliothis zea (Boddie) on soybeans relative to planting date, cultivar choice, and the use of soil-applied pesticides. Populations of H. zea and other phytophagous arthropod species, arthropod predators, and nematodes were estimated. Early to late plantings of 2 cultivars, Forrest (early maturing cultivar) and Ransom (late maturing cultivar) were treated within seed furrow, preplant band incorporation, and postplant band applications of aldicarb. In other studies, aldicarb was compared with carbofuran, ethoprop, phenamiphos, and phorate, applied to the Ransom cultivar planted late.; Early season control of the thrips, Sericothrips variabilis (Beach), and Cerotoma trifurcata (Forster) occurred on the aldicarb treatments compared with the check. Coincident to thrips populations on untreated soybeans was an increase in populations of the hemipterans, Geocoris punctipes (Say), Nabis spp., and Orius insidiosus (Say) and the coleopterous species, Coleomegilla maculata (DeGeer) and Hippodamia convergens Guerin-Meneville. Populations of H. zea larvae, however, were found to be higher on aldicarb-treated soybeans and on the later plantings of both cultivars. H. zea egg populations were similar between aldicarb-treated and untreated soybeans, but higher populations of 3rd to 6th instar larvae were attributed to increased plant growth and decreased predator populations at the time of H. zea invasion. Spring populations of pupae and adults resulting from larvae produced the previous year on aldicarb-treated and untreated soybeans were assessed.; By harvest, the nematode, heterodera glycines (Ichinoche), occurred in damaging numbers on the Ransom cultivar only. Late season phenology data showed an increase in soybean growth (especially trifoliate number per plant) in aldicarb treatments due in part to control of S. varibilis earlier in the season.; Aldicarb-treated soybeans usually required more intense insecticide suppresion to reduce H. zea larval populations to below economic threshold levels. Management of these levels required, at times, earlier and more applications of carbarylin aldicarb plots. The data showed a need to plant early and to use an early-maturing cultivar to "avoid" a late season H. zea problem. Significantly yield differences occurred between planting dates and cultivar, but not between aldicarb-treated and untreated soybeans nor between aldicarb treatments.