Is phenoloxidase involved in induced resistance to Bacillus thuringiensis kurstaki in Trichoplusia ni?
Trichoplusia ni, a pest of greenhouse crops in British Columbia, has developed significant resistance to Bacillus thuringiensis kurstaki (Btk). In the laboratory, resistance in T. ni populations rapidly declines in the absence of selection which may be due to the presence of an inducible resistance trait. Individuals from 1) a Btk resistant population, 2) a population that had reverted from resistance to susceptibility and 3) a long-term susceptible, laboratory population were exposed to a sublethal dose of Btk. Larvae from the reverted-susceptible population exhibited a significant 6-fold increase in resistance following exposure to the sublethal dose of Btk. This increase was not observed for the resistant and long-term, susceptible laboratory populations. Phenoloxidase activity and hemolymph protein concentration were measured for 1) naive larvae, 2) larvae exposed to a sublethal Btk dose for 24 hours, and 3) larvae continually exposed to a sublethal Btk dose for one week. Hemolymph
