PREPARATION OF WETTABLE POWDER FORMULATION OF BACILLUS THURINGIENSIS KD2
Formulation has always been regarded as the most important part of production in the microbial pesticides industry and one of the main concerns of producers. In this research, methods of preparation of wettable powder (WP) formulation from a Bacillus thuringiensis (Bt) isolate (KD2) were presented in which the active material (spore-crystal mixture) was increased in a liquid culture medium. The spore-crystal mixture was separated from the culture medium. Then, the mixture was dried in a drying agent with addition of 3% w/v of Triton X100, Tensiofix LX, Tensiofix BCZ in three separate treatments. The resulted technical powder was converted to wettable powder formulation by adding moisturizers, spreaders and filler materials and protective materials against ultraviolet light. Biological and physico-chemical tests including suspensibility, wettability and bioassay of the formulations as well as their phytotoxicity were done in comparison with two commercial products i.e. Biolep and Belthirul. The results of all formulations showed that the amount of suspension were 20% to 67% and the required time of wetting were 11 to 19 seconds. The results of the biological tests of formulations showed that the highest mortality rate on Helicoverpa armigera larvae was belonged to Belthirul with 78% and the lowest was recorded for Biolep with 53%. Among nine formulations, Tritonx100 + kaolin and kaolin + Lx formulations represented the better results. According to the results of LD50 and the fact that the kaolin + Lx formulation is more cost effective, this formulation is suggested for commercializing.