Identification and pathogenicity of bacteria in the Mediterranean corn borer Sesamia nonagrioides Lefebvre (Lepidoptera: Noctuidae)

Abstract

Sesamia nonagrioides (Lep.: Noctuidae) is one of the most serious pests of corn in Turkey and other Mediterranean countries. Although various cultural, chemical, and biological methods are used to control this pest, its damage still continues in all Mediterranean countries. In this study, to find an effective bacterium that can be used as a biocontrol agent against S. nonagrioides, we isolated 15 bacteria from S. nonagrioides larvae and evaluated the larvicidal potency of all isolates on the pest. According to their morphological, physiological, biochemical, and molecular properties, the isolates were identified as Achromobacter insolitus (Sn1), Morganella morganii (Sn2), Klebsiella pneumoniae (Sn3), Citrobacter freundii (Sn4), Arthrobacter protophormiae (Sn5), Chryseobacterium indologenes (Sn6), Bacillus thuringiensis (Sn7), Bacillus safensis (Sn8), Bacillus thuringiensis (Sn9), Bacillus thuringiensis (Sn10), Klebsiella pneumoniae (Sn11), Staphylococcus sciuri (Sn12), Enterobacter kobei (Sn13), Serratia marcescens (Sn14), and Microbacterium arborescens (Sn15). The results of the larvicidal activities of these isolates indicated that the mortality value obtained from all treatments varied from 25% to 93%, reaching 93% with B. thuringiensis (Sn10) for the third-instar larvae within 10 days of the application of 1.89 × 109 cfu/mL bacterial concentration at 25 °C in laboratory conditions. However, the dose-response experiments showed that increasing the concentration of bacteria gradually increased larval mortality, which reached 100% with a 2-fold concentration of Sn10. The findings of this study indicate that this isolate appears to be a promising biocontrol agent for use against S. nonagrioides.