Characterization of Bacillus thuringiensis isolates and their differential toxicity against Helicoverpa armigera populations

Bacteria from Ips sexdentatus (Coleoptera: Curculionidae) and their biocontrol potential

Ips sexdentatus (Coleoptera: Curculionidae) is one of the most destructive pests of the spruce trees in Europe. In this study, we have isolated and characterized culturable bacteria from I. sexdentatus and tested their insecticidal activity against the last instar larvae of the pest as a possible biocontrol agent. A total of eight bacterial isolates was determined and four of them were identified at species level, and the others were identified at genus level. Isolates were identified as Stenotrophomonas maltophilia (Is1), Rahnella sp. (Is2), Pseudomonas sp. (Is3), Bacillus sp. (Is4), Alcaligenes faecalis (Is5), Panteoea agglomerans (Is6), Pseudomonas fluorescens (Is7) and Serratia sp. (Is8) based on their morphological, biochemical and molecular characteristics. Insecticidal effects of bacterial isolates were performed on the last instar larvae of the pest. The highest insecticidal activity was obtained from P. fluorescens (Is7) with 73% mortality within 10 days after inoculation (p < 0.05). Mortality values of the other isolates ranged from 20 to 53%. This study suggests that Pseudomonas fluorescens (Is7) seems to be a good candidate as a possible biocontrol agent against I. sexdentatus, and provides suitable strains that can be modified to express insecticidal toxins and/or other detrimental substances to develop new control methods for I. sexdentatus.