Synergism between Bacillus thuringiensis spores and toxins against resistant and susceptible diamondback moths (Plutella xylostella)

Yong Biao Liu, Bruce E. Tabashnik, William J. Moar, Robert A. Smith

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44 Scopus citations


We studied the effects of combinations of Bacillus thuringiensis spores and toxins on the mortality of diamondback moth (Plutella xylostella) larvae in leaf residue bioassays. Spores of B. thurigiensis subsp. kurstaki increased the toxicity of crystals of B. thuringiensis subsp. kurstaki to both resistant and susceptible larvae. For B. thuringiensis subsp. kurstaki, resistance ratios were 1,200 for a spore-crystal mixture and 56,000 for crystals without spores. Treatment of a spore-crystal formulation of B. thuringiensis subsp. kurstaki with the antibiotic streptomycin to inhibit spore germination reduced toxicity to resistant larvae but not to susceptible larvae. In contrast, analogous experiments with B. thuringiensis subsp. aizawai revealed no significant effects of adding spores to crystals or of treating a spore-crystal formulation with streptomycin. Synergism occurred between Cry2A and B. thuringiensis subsp. kurstaki spores against susceptible larvae and between Cry1C and B. thuringiensis subsp. aizawai spores against resistant and susceptible larvae. The results show that B. thuringiensis toxins combined with spores can be toxic even though the toxins and spores have little or no independent toxicity. Results reported here and previously suggest that, for diamondback moth larvae, the extent of synergism between spores and toxins or B. thuringiensis depends on the strain of insect, the type of spore, the set of toxins, the presence of other materials such as formulation ingredients, and the concentrations of spores and toxins.

Original languageEnglish (US)
Pages (from-to)1385-1389
Number of pages5
JournalApplied and environmental microbiology
Issue number4
StatePublished - Apr 1998

ASJC Scopus subject areas

  • Biotechnology
  • Food Science
  • Applied Microbiology and Biotechnology
  • Ecology


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