Toxicity of some insecticides against Helicoverpa armigera (Hubner) in tomato (Lycopersicon esculentum Mill.)
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Date
2021
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AAU, Jorhat
Abstract
The research work on ‘Toxicity of some insecticides against Helicoverpa armigera (Hubner) in Tomato (Lycopersicon esculentum Mill.)’ was carried out in the laboratory and field during 2017-2018 and 2018-2019. The laboratory studieswere done in the Toxicology Laboratory, Department of Entomology. Field studies were conducted in the Experimental Farm, Department of Horticulture, Assam Agricultural University, Jorhat.
In resistance studies the field collected population of Nagaon, Darrang and Jorhat population of H. armigera showed low level of resistance to very high resistance to deltamethrin(Decis 2.8% EC) imidacloprid(Admire 70% WG), chlorantraniliprole(Coragen 18.5% SC) emamectin benzoate (Pocket 5% SG) and thiamethoxam(Eco-Champ 25% WG) upto fourth generation when reared on artificial diet. Resistance Ratio (RR), showed a range of 111.5-288.9 fold, 32.87-75.40 fold, 24.92-34.73 fold, 89.72-128.66 fold and 95-183.3 fold deltamethrin, imidacloprid, chlorantraniliprole, emamectin benzoate and thiamethoxam, respectively for the H. armigera population collected from Nagaon. The population collected from Darrang showed a Resistance Ratio (RR) of 103.13-190.30 fold,28.84-60.90 fold, 24.1-33.46 fold,24.1-116 fold, 102.15-203.50 fold for deltamethrin, imidacloprid, chlorantraniliprole,emamectin benzoate and thiamethoxam, respectively. While, for Jorhat population the range of Resistance Ratio (RR) were 106.29-236.92 fold, 23.02-63.14 fold, 10.07-34.34 fold, 10.07-88.83 fold and 98.38-168.4 foldfor deltamethrin, imidacloprid, chlorantraniliprole,emamectin benzoate and thiamethoxam, respectively.The field population collected Nagaon district population showed very high resistance to deltamethrin, emamectin benzoateand thiamethoxam (RF: >100), high resistance to imidacloprid (RF: 31-100) and moderate resistance to chlorantraniliprole (RF: 11-30). In case of population collected from Darrang district, deltamethrin and thiamethoxam registered very high resistance, emamectinbenzoate and imidacloprid showed high resistance and moderate resistance observed onchlorantraniliprole. However, the field collected population of Jorhat showed low resistance to chlorantraniliprole (RF: 2-10), moderate to emamectinbenzoate (RF:11-30), high resistance to Imidacloprid and very high resistance to deltamethrin and thiamethoxam (RF:>100). At all three places it was observed that H. armigeraalready developed very high resistance todeltamethrin and thiamethoxam. Bio efficacy studies, all the
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treatments viz.,deltamethrin @ 15 g a.i./ha,imidacloprid @ 20 g a.i./ha,chlorantraniliprole @ 10 g a.i./ha, emamectin benzoate @ 11g a.i./ha and thiamethoxam @ 26 g a.i./ha were found to be significantly superior over control (untreated). The highest population reduction was observed with the treatment of chlorantraniliprole @ 10 g a.i./ha at one (55.47%), three (75.47%), seven (85.18%), ten day (87.26%) and fifteen (87.07%) days after spraying during 2017-18 and 2018-19 whereas lowest atdeltamethrin @ 15 g a.i./ha (35.74%, 49.43%, 58.58%, 63.20% and 64.25%, respectively). However, in control, population was increased by 1.97%, 4.03%, 8.52%, 10.76% and 13.90% at 1, 3, 7, 10 and 15 days after spraying. The highest mean yield was obtained fromchlorantraniliprole @ 10 g a.i./ha (0.22 q/ha) followed byemamectin benzoate @ 11g a.i./ha(0.21 q/ha),thiamethoxam @ 26 g a.i./ha (0.20 q/ha),imidacloprid @ 20 g a.i./ha (0.19 q/ha) and deltamethrin @ 15 g a.i./ha (0.15 q/ha). The lowest yield was obtained at control (0.12 q/ha). All the treatments gave significantly higher yield over control. Chlorantraniliprole @ 10 g a.i./ha registered highest cost: benefit ratio (1 : 5.01) and successfully reduced the aphid population.The LC50values of deltamethrin, imidacloprid, chlorantraniliprole, emamectin benzoate and thiamethoxam to susceptible laboratory reared AAU collected H.armigera were 0.0063, 0.0042, 0.0035, 0.0038 and 0.0039 per cent after 24 hrs and0.0046, 0.0016, 0.0011, 0.0015, 0.0014 per cent after 48 hrs respectively. The residual toxicity of chlorantraniliprole @ 10 g a.i./ha in tomato to 7 days old larva of H. armigera was highest (85.00% and 87.50% mortality) at 24 and 48 hrs exposure period when treated terminal shoots and fruits were fed after one day of spraying while deltamethrin @ 15 g a.i./ha treated terminal shoots and fruits caused lowest larval mortality (45.00% and 50.00%). The highest PT and RPT values were observed at chlorantraniliprole @ 10 g a.i./ha (1050 and 2.18 respectively) followed by emamectin benzoate @ 11 g a.i./ha (990 and 2.06), thiamethoxam @ 26 g a.i./ha (937.50 and 1.95), imidacloprid @ 20 g a.i./ha (810 and 1.68) and deltamethrin @ 15 g a.i./ha (480 and 1.00).Considering the results ofbio efficacy, relative and residual toxicity, fruit borer population reduction, yield, cost-benefit ratio, application ofchlorantraniliprole @ 10 g a.i./ha can be suggested for field application for management of H. armigerapopulation or can be incorporated in IPM of H. armigera. Moreover, these new chemicals chlorantraniliprole @ 10 g a.i./ha, emamectin benzoate @ 11 g a.i./ha and thiamethoxam @ 26 g a.i./ha can be used in rotation or combination for resistance management.