Distance, Rotation, and Border Crops Affect Colorado Potato Beetle (Coleoptera: Chrysomelidae) Colonization and Population Density and Early Blight (Alternaria Solani) Severity in Rotated Potato Fields

Abstract

The effect of distance between rotated potato fields on Colorado potato beetle, Leptinotarsa decemlineata (Say), and early blight, Alternaria soiani , incidence was evaluated for 2 yr. In eight newly established potato fields, the timing of adult beetle colonization, population densities, and early-season defoliation were related closely to how isolated the fields were from the previous year’s planting. Even short distances between rotated locations resulted in significant reductions of Colorado potato beetle densities. An integrated pest management program resulted in an inverse relationship between distance and the number of insecticides applied for the Colorado potato beetle. Compared with a nonrotated field, a distance of 0.3 to 0.9 km was sufficient to reduce insecticide requirements by 50%. Winter wheat and hay buffers Significantly delayed overwintered adult colonization compared with fallow corn stubble. Early blight severity decreased as the distance between the rotated locations increased. Colorado potato beetle population densities, defoliation, and early blight severity followed a similar exponential decline with distance. The effects of winter wheat and hay buffer crops on beetle infestations and early blight severity were also similar. Factors that reduced early-season Colorado potato beetle immigration also lowered the early blight severity.