BIOLOGICAL CONTROL Synergy Between Zwittermicin A and Bacillus thuringiensis subsp. kurstaki Against Gypsy Moth (Lepidoptera: Lymantriidae)

Bacillus cereus French & French increased the mortality of 3rd-instar gypsy moths, Lymantriadispar(L.), causedbyBacillus thuringiensis subsp.kurstakiBerliner.B. cereusdidnotcause mortality of L. dispar when applied alone. The activity of various B. cereus strains was correlated positively with their accumulation of zwittermicin A, an aminopolyol antibiotic, in culture. When a constant dose of B. thuringiensis subsp. kurstaki and increasing concentrations of puriÞed zwittermicin A were applied to artiÞcial diet, mortality of larvae was directly proportional to the dose of zwittermicinA.ZwittermicinAby itself causednomortality at the concentrations tested.Addition of zwittermicin A to a culture of a mutant strain of B. cereus that does not accumulate zwittermicin A restored synergistic activity. These results indicate synergybetweenB. thuringiensis subsp. kurstaki and zwittermicin A. The potential for enhancing efÞcacy of B. thuringiensis and delaying development of insect resistance are discussed.