FIELD STUDIES ON THE POPULATION DYNAMICS AND MANAGEMENT OF CORN ROOTWORMS
Abstract
Field studies were conducted during 1980-1982 to determine the occurrence of economic injury to corn from corn rootworm (CRW) larvae and to compute treatment thresholds from larval counts. Economic root damage did not occur in these studies until ca. 22 June. However, larval counts collected prior to 22 June were not often correlated with subsequent damage. Economic thresholds of 0.2 - 1.9 larvae/plant were calculated from samples collected on 11 June. Thresholds increased with time, up to 7.3 larvae/plant, for samples collected on or after 22 June. The effects of planting date and insecticide-application time on CRW control were investigated from 1980-1982. Planting date had a significant impact on efficacy. Postplanting treatments applied on or after 22 June seldom prevented economic injury, if corn was planted before 10 May. There were minimal differences associated with application time on corn planted on or after 10 May. The impact of planting date and pattern on CRW population dynamics was examined in 1981 and 1982. Delaying planting significantly reduced CRW numbers and delayed the time of occurrence of 2nd and 3rd instars and pupae and adult emergence. Solid-seeding of corn significantly decreased CRW numbers, compared with conventional planting, but did not significantly impact seasonal occurrence. The phenology of CRW populations was related to calendar date and heat-unit accumulations. Seasonal occurrence was a linear function of planting date. The occurrence of 2nd and 3rd instars and pupae and adult emergence were consistent among populations according to Julian date and soil heat-units. Phenology according to air heat-units was inconsistent.
Degree
Ph.D.
Subject Area
Entomology
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