Evaluation of the effectiveness of entomopathogens for the control of colorado potato beetle, leptinotarsa decemlineata (Coleoptera: Chrysomelidae)

Abstract

Colorado potato beetle, Leptinotarsa decemlineata (Coleoptera: Chrysomelidae) damages potato, tomato, and eggplant, and is one of the most serious agricultural pests all over the world. Due to its resistance against chemical insecticides and some biopesticides, new biocontrol agents compatible with different ecological conditions are needed urgently for the integrated pest management programs of this pest. For this purpose, we studied the insecticidal effects of thirteen indigenous microbial isolates including entomopathogenic bacteria, fungi, and nematodes from our culture collection against L. decemlineata with screening and dose-response tests under laboratory conditions. Bacillus thuringiensis strain Xd3 caused 83% and 73% mortality against larvae and adults of the pest at 10(9) CFU mL(-1) concentration within 10 days, respectively. While fungal isolate Metarhizium anisopliae Gg-12 yielded 98% mortality with 107 conidia mL(-1) concentration on larvae at 15 days, mortality provided by Gg-12 on adults reached 100% at the same concentration and period. Steinernema websteri AS1 was determined as the most effective entomopathogenic nematode with 92% mortality within seven days on larvae. Based on probit analysis, the LC50 values of B. thuringiensis Xd3 against larvae and adults were calculated as, respectively, 1.73x10(6) and 1.69x10(7) CFU mL(-1), and that of M. anisopliae Gg12 were 1.18x10(4) and 6.2x10(3) conidia mL(-1), and that of S. websteri AS1 was 117 IJs mL(-1). Considering these results, the biopesticides developed from these isolates can be used safely and successfully in the pest management control programs of Colorado potato beetle.