PALATABILITY OF FLOUR GRANULAR FORMULATIONS TO EUROPEAN CORN-BORER LARVAE (LEPIDOPTERA, PYRALIDAE)

Newly developed techniques for producing starch and flour granule form ulations encapsulating Bacillus thuringiensis Berliner have led to a l arge number of potentially effective baits for Ostrinia nubilalis (Hub ner). One aspect of these formulations that must be considered is thei r palatability to com borer larvae. Experiments were conducted to dete rmine palatability of several formulations in two-choice preference te sts. Com borer larvae preferred flour granules containing cotton leave s or a commercially available feeding stimulant, Coax, or both. Larvae rejected granules formulated with CaCl2. Granules made with molasses were intermediate in palatability. When the granules were formulated w ith 1,600 International Units (IU) B. thuringiensis per mg granules an d 20 mg of granules were sprinkled on cotton leaves, several formulati ons killed >70% of the corn borer larvae that fed on treated leaves; o ther formulations killed <40% of the test insects. Mortality was reduc ed when larvae were exposed to cotton leaves sprinkled with granules f ormulated with CaCl2 when compared with those formulated with cotton l eaves or Coax, or both. The dose of B. thuringiensis could be reduced by 3/4 (i.e., to 400 IU/mg) without affecting the level of larval mort ality if the pathogen was entrapped in granules containing cotton leaf tissue + Coax or only cotton leaf tissue.