Isolation and characterization of Bacillus megaterium isolates from dead pentatomids and their insecticidal activity to Palomena prasina nymphs

Abstract

Bacillus megaterium isolates, were demonstrated to be efficient biocontrol agents against the green shield bug ( Palomena prasina L., Heteroptera : Pentatomidae ). Firstly hazelnut orchards were surveyed and four B. megaterium isolates were obtained from P. prasina . The morphological, physiological and biochemical characteristics of B. megaterium isolates were determined according to the standardized methodology. Additionally 16S rRNA gene sequence analyse was performed to determine the isolates. Analysis of the 16S rRNA gene confirmed that isolates Sa-1, Sa-5, SAk-2 and SAkc-19 are B. megaterium , with 100% sequence homology to the type strains of B. megaterium . Effectiveness of these isolates was tested against P. prasina nymphs in laboratory, at 25±1°C and 70±5 RH. Isolates were bioassayed against nymphs and dead individuals were counted daily, following a 12 days lasting treatment. Lethal time (LT 50 and LT 90 ) values of B. megaterium isolates were calculated. LT 50 values of the two most active isolates were 1.91 and 11.18 days. The highest mortality rate was 98% obtained with the treatment of SAkc-2 isolates at concentrations of 10 8 cfu ml -1 on the 12 th day of post treatment.