Managing the Colorado potato beetle (Coleoptera: Chrysomelidae) with straw mulch and encapsulated Bacillus thuringiensis bioinsecticide
Abstract
The impact of straw mulch, esfenvalerate insecticide and Bt biological insecticide on Colorado potato beetle, Leptinotarsa decemlineata (Say), natural enemies of the pest, potato plant growth and yield, were studied at the O'Neall and Pinney Purdue farms in 1992 and 1993. The counts of first plus second, and third plus fourth instars, adults, percentage of potatoes that had larvae or adult beetles on them as well as rating of damage by the beetle, based on a 1 to 5 rating which increased with plant damage level, was lower on mulched than on non mulched plots on most of the sampling dates. Esfenvalerate provided the best protection against the beetles while Bt provided protection that was intermediate between esfenvalerate and the control. Mulch and esfenvalerate treated plots had taller plant than the control plants. Indigenous predators of the beetle, that is, Colleomegilla maculata (DeGeer), Coccinella septempunctata (L), Lebia grandis Hentz, Podisus maculiventris (Say), and Perillus biculatus (F.) were more abundant on non mulched than on mulched potato plots, and on Bt and control plots than on esfenvalerate plots. The spatial distribution of the beetle predators followed that of the beetle hosts. This finding suggests that a combination of straw mulch and Bt could be used to sufficiently suppress the Colorado potato beetle population when the beetle infestation is low. Mulch also kept the soil cool and moist, resulting in improved plant growth and crop yield. A mulch and Bt treatment combination would not affect the natural enemies directly, thus the environment would remain free of undesirable residues.
Degree
Ph.D.
Advisors
Foster, Purdue University.
Subject Area
Entomology
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