Evaluation of Some Insecticides for the Control of Brahmina coriacea (Hope) in Himachal Pradesh
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Date
2018-09-29
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CSKHPKV, Palampur
Abstract
The bioassay study of six insecticides viz. chlorantraniliprole, bifenthrin, clothianidin, thiamethoxam, imidacloprid and chlorpyriphos was conducted against grubs and adults of Brahmina coriacea (Hope). Against grubs, these chemicals were evaluated through dip treatment. The LC50 values of chlorantraniliprole for I - III instar grubs of B. coriacea were calculated to be 70.65, 213.30 and 226.1 ppm, while in case of bifenthrin, the LC50 values were determined as 100.2, 259.90 and 337.10 ppm. The LC50 values of clothianidin for I - III instar grubs were calculated to be 139.51, 266.12 and 348.30 ppm. Imidacloprid produced 50 per cent kill (LC50) at a concentration of 156.12, 415.58 and 622.04 ppm in I - III instar grubs, and for thiamethoxam the respective LC50 values were computed to be 205.89, 477.31 and 626.67 ppm. Chlorpyriphos was found to be least toxic among tested chemicals, and it produced 50 per cent kill of I - III instar grubs of B. coriacea at a concentration of 222.60, 506.92 and 556.72 ppm, respectively. These six soil insecticides were also evaluated against adults of B. coriacea by releasing the beetles in soil, contaminated with different insecticides. Among these, chlorantraniliprole was found to be highly effective. The LC50 value of chlorantraniliprole was calculated to be 0.022 g a.i./kg soil. In bifenthrin, and clothianidin the LC50 values were determined to be 0.028 g a.i./kg soil and 0.034 g a.i./kg soil. Thiamethoxam produced 50 per cent kill of beetles at a dose of 0.047 g a.i./kg soil. The LC50 values of chlorpyriphos and imidaclprid for adults of B. coriacea were calculated to be 0.058 g a.i./kg soil and 0.066 g a.i./kg soil. The order of toxicity of tested soil insecticides to beetles was chlorantraniliprole > bifenthrin > clothianidin > thiamethoxam > chlorpyriphos > imidacloprid. All tested soil insecticides at low doses (1.20×10-4 - 0.15×10-4 g a.i./kg soil) induced reduction in egg laying by females beetles of B. coriacea. The egg production decreased in a dose dependent manner in all the treatments. The average number of eggs laid in different treatments ranged from 28.4 - 44.8 eggs/3 females. Maximum curtailment in egg laying was observed in bifenthrin (82.06 %), followed by chlorpyriphos (79.28 %). Against beetles of B. coriacea, dimethoate, indoxacarb, flubendiamide, spinosad, fenazaquin, mancozeb and dodine were tested by leaf dip and topical application methods. In leaf dip method, the LC50 values of dimethoate, indoxacarb, flubendiamide, spinosad and fenazaquin were calculated to be 8.41, 165.20, 186.66, 246.09 and 460.60 ppm, respectively. The order of toxicity was dimethoate > indoxacarb > flubendiamide > spinosad > fenazaquin. Among fungicides, mancozeb and dodine were tested. Mancozeb produced mortality in a dose - dependent manner and its LC50 value was calculated to be 994.96 ppm. Dodine did not induce any beetle mortality up to 2000 ppm. In topical application method, the LC50 values for indoxacarb, dimethoate, flubendiamide, fenazaquin and spinosad were determined to be 69.71, 201.90, 415.42, 474.66 and 492.19 ppm, and the order of toxicity was indoxacarb > dimethoate > flubendiamide > fenazaquin > spinosad. Irrespective of insecticides, leaf dip method proved more effective, except indoxacarb.
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