Synergism between CryIA insecticidal crystal proteins and spores of Bacillus thuringiensis, other bacterial spores, and vegetative cells against Lymantria dispar (Lepidoptera: Lymantriidae) larvae

The lethality of CryIA(a) and CryIA(c) insecticidal crystal proteins from Bacillus thuringiensis to gypsy moth, Lymantria dispar (L.), was significantly enhanced by the presence of either bacterial spores or vegetative cells of Escherichia coli and several forest epiphytic bacteria. Spores from B. cereus, B. megaterium, and B. subtilis were as effective synergizers of the CryIA insecticidal crystal proteins as spores from an acrystalliferous strain of B. thuringiensis (HD-73 cry(-)). Klebsiella sp., K. pneumonia, Erwinia amylovora, E. rubrifaciens, Pseudomonas fluorescens, Xanthomonas sp., X. campestris, Actinomyces sp. Corynebacterium sp., Flavobacterium sp., and Escherichia coli were effective synergizers of at least one of the CryIA toxins. Only P. syringae was not synergenic. In the absence of the CryIA toxins, none of the bacterial cell or spore synergists exhibited toxicity or inhibited larval growth or molt to the next instar.