APTNESS OF INSECTICIDES (BACILLUS-THURINGIENSIS AND CARBOFURAN) WITH ENDOPHYTIC BEAUVERIA-BASSIANA, IN SUPPRESSING LARVAL POPULATIONS OF THE EUROPEAN CORN-BORER

Research was conducted in 1989 and 1990 to determine if Beauveria bass iana in combination with Bacillus thuringiensis or carbofuran is an ef fective tactic for season-long management of the European corn borer, Ostrinia nubilalis. A granular formulation of Beauveria bassiana was a pplied to corn at whorl stage (V6) and/or at pollen-shed stage (R1) co rn. Bacillus thuringiensis or carbofuran was then applied to the same plants. Beauveria bassiana reduced larval populations of O. nubilalis when the fungus was applied to corn during both the whorl stage and th e pollen-shed stage. When either Bacillus thuringiensis or carbofuran was added to plants treated with Beauveria bassiana, there was increas ed mortality of O. nubilalis. Although Beauveria bassiana alone reduce d O. nubilalis tunneling, mostly damage was further reduced when Bacil lus thuringiensis or carbofuran was applied to whorl-stage corn. When applied to pollen-shedding corn, Beauveria bassiana reduced tunneling but had no significant effect on yield, unless Bacillus thuringiensis was added. Although Beauveria bassiana, Bacillus thuringiensis, and ca rbofuran reduced tunneling by first generation O. nubilalis, increased yields did not always result. Tunneling by second-generation O. nubil alis was significantly reduced by Beauveria bassiana in both years of all experiments, Even so, yields were variable in all experiments whic h indicated that a number of abiotic and biotic factors, aside from in sects, affected yields. This study is the first to document compatibil ity of Beauveria bassiana with a chemical insecticide. Yield data indi cate that endophytic Beauveria bassiana is nor a plant pathogen.