Response of the Cottonwood Leaf Beetle (Coleoptera: Chrysomelidae) to Bacillus thuringiensis var. san diego

Abstract

A standardized laboratory bioassay was used to quantify the lethal and sub-lethal responses of larval and adult cottonwood leaf beetles, Chrysomela scripta F., to Bacillus thuringiensis var. san diego, formulated as M-One standard powder (Mycogen Corporation, San Diego). The median lethal concentration (LC₅₀) for second instars, after a 96-h exposure to B. thuringiensis var. san diego, was 21,000 Colorado potato beetle international units per milliliter water. The LC₅₀ estimates for the third instars and adults were 20 and 40 times higher than for second instars, respectively. Larval LC, ₅₀ estimates were halved when mortality for the entire larval period was included in the LC, ₅₀ estimate. Adult mortality continued for approximately 14 d after initial exposure to Bacillus thuringiensis var. san diego. The adult LC₅₀ calculated at 14 d was half the 4-d estimate. Age of adults at treatment did not significantly affect the LC₅₀. Median lethal times (LT₅₀) were similar for larvae and adults, with overlapping confidence limits ranging from 2.1 to 3.5 d. Larvae surviving treatments as second and third instars showed a significant dose-dependent decrease in adult dry weight at eclosion and an increase in the larval developmental period.

Citation

Bauer, Leah S. 1990. Response of the Cottonwood Leaf Beetle (Coleoptera: Chrysomelidae) to Bacillus thuringiensis var. san diego. Environmental Entomology 19(2):428-431