Evaluation of Thuricide 48Lv Against Douglas-Fir Tussock Moth Reared on Various Host Plants, Laboratory Bioassay, 1992

Abstract

Abstract Trials were conducted to determine the relative susceptibility of different larval stages of Douglas-fir tussock moth to the Bacillus thuringiensis insecticide Thuricide 48LV. Cultures were established from egg masses collected near Vail, CO and larvae were maintained on either white fir, Douglas-fir, or blue spruce foliage. Once larvae were started on a particular host plant, they were fed only that type of food. They were maintained with fresh foliage as needed, and transferred to clean petri dishes when food was changed. Instar II-IV was used for bioassay and were divided into groups of 10, with ten replications for each food type. Foliage was dipped in a 1:400 dilution of Thuricide 48LV, allowed to air dry and subsequently fed to larvae. Mortality was assessed at various intervals between 48 and 213 hours after initial exposure.