Investigating internal bacteria of Spodoptera littoralis (Boisd.) (Lepidoptera: Noctuidae) larvae and some Bacillus strains as biocontrol agents

Abstract

Spodoptera littoralis (Boisd.) (Lepidoptera: Noctuidae) is one of the most destructive pests of several vegetables and fruits worldwide. In spite of various control methods, this pest has still continued to cause signifcant damage. In this study, the culturable bacterial fora of S. littoralis was determined. New isolates from S. littoralis, as well as 12 diferent Bacillus isolates belong to 5 species that were previously isolated from diferent pests, were tested on S. littoralis larvae. In total, 9 bacteria were characterized based on their morphological, biochemical, physiological, and molecular characteristics. Te bacterial fora of S. littoralis was determined as Flavobacterium sp. (SL1), Klebsiella pneumonia (SL2), Enterobacter sp. (SL3), Enterobacter sp. (SL4), Klebsiella sp. (SL5), Serratia marcescens (SL6), Pseudomonas aeruginosa (SL7), Acinetobacter baumannii (SL8), and Staphylococcus sp. (SL9). Te insecticidal activity tests were performed on the third-instar larvae of S. littoralis. SL1 and SL5 from S. littoralis caused the highest mortalities with 67% and 77%, respectively. Among previously isolated Bacillus isolates, Bacillus thuringiensis subsp. kurstaki (MnD) and B. thuringiensis subsp. kurstaki (BnBt) were found to be the most efective, causing 100% mortality within 10 days afer treatment. A concentration-response test was conducted with these isolates and it was found that the isolate MnD was more efective than BnBt. Terefore, further bioassay experiments were conducted with the isolate MnD and results were discussed with respect to the biocontrol potential of the bacterial isolates.Spodoptera littoralis (Boisd.) (Lepidoptera: Noctuidae) is one of the most destructive pests of several vegetables and fruits worldwide. In spite of various control methods, this pest has still continued to cause signifcant damage. In this study, the culturable bacterial fora of S. littoralis was determined. New isolates from S. littoralis, as well as 12 diferent Bacillus isolates belong to 5 species that were previously isolated from diferent pests, were tested on S. littoralis larvae. In total, 9 bacteria were characterized based on their morphological, biochemical, physiological, and molecular characteristics. Te bacterial fora of S. littoralis was determined as Flavobacterium sp. (SL1), Klebsiella pneumonia (SL2), Enterobacter sp. (SL3), Enterobacter sp. (SL4), Klebsiella sp. (SL5), Serratia marcescens (SL6), Pseudomonas aeruginosa (SL7), Acinetobacter baumannii (SL8), and Staphylococcus sp. (SL9). Te insecticidal activity tests were performed on the third-instar larvae of S. littoralis. SL1 and SL5 from S. littoralis caused the highest mortalities with 67% and 77%, respectively. Among previously isolated Bacillus isolates, Bacillus thuringiensis subsp. kurstaki (MnD) and B. thuringiensis subsp. kurstaki (BnBt) were found to be the most efective, causing 100% mortality within 10 days afer treatment. A concentration-response test was conducted with these isolates and it was found that the isolate MnD was more efective than BnBt. Terefore, further bioassay experiments were conducted with the isolate MnD and results were discussed with respect to the biocontrol potential of the bacterial isolates.