Field evaluation of Bithurin, a commercial formulation of Bacillus thuringiensis against stripped stem borer, Chilo suppressalis Walker

Bacillus thuringiensis (Bt) is widely used in two forms, toxic crystal and a mix of spores and crystal for controlling of harmful insects. This research carried out in order to evaluate the effect of Bithurin on striped stem borer, Chilo suppresslis (SSB) under field conditions in Rasht during 2010. The experiment was conducted in a complete randomized design with two factors including: Dose and usage times with 3 replications. Results showed that 1.5 and 1 liter per hectare with two and three application times of Bithurin had the most effect on SSB and reduced the percentage of dead hearts to 0.42 and 0.47 %, respectively. Also, the highest efficacy in first generation of SSB was observed in the treatment of 1.5 liter per hectare with three times spraying (61.22%). In this study, spraying of one liter Bithurin with three times per hectare in the rice vegetative stage reduced the percentage of dead hearts to 0.52% in comparison with control. In reproductive stage of rice, percentage of the lowest infection white heads observed in 1.5 liter per hectare in plots with two and three times application, 0.78 and 0.83%, respectively. Also, the highest efficacy observed in plots with 1.5 liter per hectare with two and three times application in comparison with control (42.93 and 48.48%), respectively. Infection of white heads reduced by 3.84% in comparison with control in rice field. Therefore, if in a field infection is higher than the norm, 2-3 times of spraying can be recommended.