Influence of Planting Dates on the Efficacy of Soil Insecticides Applied to Control Larvae of the Western and Northern Corn Rootworm12

Abstract

In a 3-year study from 1974–76, planting dates significantly ( P <0.05) influenced the control provided by soil insecticides applied at planting time to control larvae of the western corn root worm, Diabrotica virgifera LeConte, and the northern corn root worm, D. longicornis (Say). With the exception of the June plantings (damage was extremely reduced in all treatments), most of the insecticide treatments provided slightly more root protection when applied to later plantings of corn. When the June plantings were omitted from the analysis, there was still a significant planting date effect in the 1974 and 1975 studies but not in the 1976 test. There was a significant planting date X insecticide interaction each year. Applications of carbofuran and fonofos provided the least variable control and phorate and fensulfothion resulted in the most variable control over the planting dates of the insecticides included in the study.