Neonate tiger swallowtail larvae (Papilio glaucus) were used to bioassay the effects of Btk (Bacillus thuringiensis var. kurstaki) at 4 doses (0.268, 0.034, 0.008, and 0.004 BIU per cm leaf surface) with an untreated control. Larvae, obtained from females captured in Georgia and North Carolina, were fed leaves of either tulip tree (Liriodendron tulipfera) or black cherry (Prunus serotina) in experiments that either included a pre-treatment dip and rinse in 5% chlorox bleach or not, before the application of Btk (dipping leaves in serially diluted solutions of Foray 48B).
The results show no difference between North Carolina and Georgia P. glaucus larval dosage sensitivities, but do illustrate a clear dosage effect for all 4 treatments (cherry with and without bleach pre-treatment; tulip tree with and without bleach pre-treatment). The larvae on the bleached leaves do not do better (for cherry or tulip tree host plant) as would be expected if microbial symbionts on the phylloplane synergize the Btk toxicity. These results show that Btk (at doses several thousand-fold less than aerial sprays across forests for gypsy moth control) will kill P. glaucus, with or without microbial synergism on leaf phylloplanes
