Grain loss caused by Tribolium castaneum, Sitophilus oryzae and Acanthoscelides obtectus in stored durum wheat and beans treated with Beauveria bassiana

The effect of the fungal entomopathogen Beauveria bassiana (Balsamo) Vuille min (Hyphomycete) on the losses caused to durum wheat and beans by storage insects was investigated. Grains were infested with Tribolium castaneum (He rbst), Sitophilus oryzae (L.) and Acanthoscelides obtectus (Say). Beauveria bassiana was produced in inoculated autoclaved rice. The spore formulation (ground rice and B. bassiana) was applied to grain (wheat or bean) and sha ken to evenly cover the grain. Adults of T. castaneum or S. oryzae were add ed to wheat and adults of A. obtectus to bean. Five replicates were set up for each treatment and controls (milled rice but no conidia). The insectici dal effect of B. bassiana was tested by measuring the fresh weight and weig ht loss of grains after four months of storage. Wheat grains infested with S. oryzae without the conidia was significantly more damaged by weevils tha n grains treated with B. bassiana. The mean fresh weight of grains with the conidia was significantly greater (18.4%) than the corresponding mean with out the fungus when S. oryzae were present. Percentage weight loss decrease d by 81.5% and was significantly smaller than the loss from the untreated g rain. Significant differences were not found in the fresh weight of seed in fested with T. castaneum or A. obtectus in treated or untreated grain nor i n the percentage weight loss of grains infested with these insects, with an d without B. bassiana. (C) 2001 Elsevier Science Ltd. All rights reserved.