Effect of moisture content, substrate and nutritional supplements on condition and virulence of Beauveria bassiana against greenhouse whitefly Trialeurodes vaporariorum

For cost-effective mass production of entomopathogenic fungi, it is necessary to evaluate the effect of a low-cost culture media on condition and virulence of entemopathogenic fungi. The objective of this research was to evaluate the effect of moisture content, substrate and nutritional supplements on condition and virulence of Beauveria bassiana against greenhouse whitefly. The water requirement of B. bassiana A1-1 for mass production on wheat bran, rice bran, corn bran, rice husk, rolled oat, and the used barley residues in insectariums, was initially evaluated at the ratio of 0.5:1, 1:1 and 1.5:1 (distilled water: culture medium). Then, the effect of whey and molasses on the condition of this fungus was evaluated. The virulence of conidia harvested from wheat bran, rice bran, corn bran and barley substrates was also investigated on greenhouse whitefly nymphs in laboratory and greenhouse conditions. Wheat bran and rice bran in water ratio of 0.5:1 (distilled water: culture medium) showed the highest yield with an average of 5.3 × 1010 and 5.1 × 1010 conidia per gram of substrate, respectively. In the test of the effect of nutritional supplements, except to barley substrate, the addition of whey increased the condition in other substrates. In laboratory bioassay, all treatments showed between 80 and 87% mortality, but in the greenhouse bioassays, the produced conidia on rice bran, corn bran and wheat bran caused 56 ± 1.87, 52 ± 2.54 and 49 ± 2.91% mortality, respectively. According to results, rice bran, corn bran and wheat bran are introduced as suitable substrates for mass production of the studied fungal isolate.