Bacterial pathogens from Diprion pini L. (Hymenoptera: Diprionidae) and their biocontrol potential

Abstract

Microbial insecticides have become increasingly important in recent years for the control of insect pests. Among microbial insecticides, insect pathogenic bacteria and their toxins have been the most commercially successful and hold potential for further development. In this study, we investigated the isolation and identification of some potential pathogenic bacteria from Diprion pini L. (Hymenoptera: Diprionidae) which is a serious pest of pine forests worldwide. A total of eighteen bacteria were isolated, ten bacteria from dead D. pini larvae and eight bacteria from healthy larvae. The bacterial strains were characterized by their morphological features, 16 S rRNA gene sequencing and phylogenetic analysis. In addition, these bacteria and four Bacillus thuringiensis strains (isolated from pine forest soil) were tested against D. pini larvae under laboratory conditions. The bacterial isolates were identified as Kluyvera intermedia O-1, O-8, O-10 and S-3, Proteus mirabilis O-2, Klebsiella oxytoca O-3, Bacillus sp. O-4, Pantoea agglomerans O-5 and S-5, Serratia marcescens O-6, Pseudomonas sp. O-7, Acinetobacter sp. O-9, Enterobacter sp. S-1 and S-9, Bacillus pumilus S-2, Enterobacter cancerogenus S-4, Pseudoclavibacter sp. S-6 and Arthrobacter sp. S-8. All isolates showed different insecticidal activity against the pest and the highest mortality was obtained from P. mirabilis O-2 with 100% within ten days after exposure. The highest mortality among B. thuringiensis strains was obtained from B. thuringiensis 37 - 4 with 56.67%. This is the first study of determination of the culturable bacterial diversity within D. pini and the obtained results might be beneficial for biocontrol of D. pini.

Microbial insecticides have become increasingly important in recent years for the control of insect pests. Among microbial insecticides, insect pathogenic bacteria and their toxins have been the most commercially successful and hold potential for further development. In this study, we investigated the isolation and identification of some potential pathogenic bacteria from Diprion pini L. (Hymenoptera: Diprionidae) which is a serious pest of pine forests worldwide. A total of eighteen bacteria were isolated, ten bacteria from dead D. pini larvae and eight bacteria from healthy larvae. The bacterial strains were characterized by their morphological features, 16 S rRNA gene sequencing and phylogenetic analysis. In addition, these bacteria and four Bacillus thuringiensis strains (isolated from pine forest soil) were tested against D. pini larvae under laboratory conditions. The bacterial isolates were identified as Kluyvera intermedia O-1, O-8, O-10 and S-3, Proteus mirabilis O-2, Klebsiella oxytoca O-3, Bacillus sp. O-4, Pantoea agglomerans O-5 and S-5, Serratia marcescens O-6, Pseudomonas sp. O-7, Acinetobacter sp. O-9, Enterobacter sp. S-1 and S-9, Bacillus pumilus S-2, Enterobacter cancerogenus S-4, Pseudoclavibacter sp. S-6 and Arthrobacter sp. S-8. All isolates showed different insecticidal activity against the pest and the highest mortality was obtained from P. mirabilis O-2 with 100% within ten days after exposure. The highest mortality among B. thuringiensis strains was obtained from B. thuringiensis 37 - 4 with 56.67%. This is the first study of determination of the culturable bacterial diversity within D. pini and the obtained results might be beneficial for biocontrol of D. pini.