Various effects of methanolic extract of neem seed kernel on larvae of cotton boll worm, Helicoverpa armigera (Hubner) (Lepidoptera: Noctuidae) were studied and compared with those of Neem Azal T/S and Neem Plus, two commercial formulations. The pest was collected from Gorgan (Golestan Province, Iran) and reared on a bean based artificial diet. The neem seed was collected from Bandar-Abbas (Hormozgan Province) and extracted in laboratory. Growth inhibitory and antifeedant assays were carried out on larvae treated with seed kernel extracts in 3 concentrations,1, 2.5 and 5%, under choice and no-choice conditions. The neem extract had a significant antifeedancy effects on larvae. Neem Plus and 5% extract had the least and most antifeedancy effects, respectively. The most and least feeding rates belonged to Neem Plus and Neem Azal treatments, respectively, which differed significantly (P<0.05). Feeding deterrence index (FDI) was highest in 5% extract which also differed significantly from Neem Plus treatment. Larvae treated with extract led to malformation and prevented formation of pupa and ultimately caused death. The LT50 values with confidence limit (CL) of 95% were 3.84 and 4.13 d, for Neem Azal and 5% extract respectively. DC50 and EC50 of extract were 4.73% and 2.73% at similar CL, respectively.

Keywords: Neem seed kernel, Methanol extract, Neem Azal, Neem Plus, Cotton bollworm.

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