Action of Bacillus thuringiensis preparation against larch bud moth, Zeiraphera diniana (Gn.), enhanced by beta-exotoxin and DDT.

Addition of either DDT or the supernatant of a centrifuged liquid culture of Bacillus thuringiensis, serotype H1, containing beta-exotoxin, enhanced the action of the bacterial preparation Thuricide 90 T against larvae of the larch pest Zeiraphera diniana, increasing mortality from 53% to more than 80%. Since DDT alone produced 57% mortality, its combined action corresponds to independent action. The preparation of beta-exotoxin, on the other hand, had only little effect alone but synergized the action of the bacterial preparation considerably.