Bioefficacy and dissipation of imidacloprid and thiacloprid in/on chilli (Capsicum annuum L.)
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Date
2018-10
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Abstract
Chilli (Capsicum annuum L.) is an important vegetable and spice of India. India is the largest producer of chilli in the world. Although, its share in global production is high, there are still a number of factors that limits its production and productivity and one being infestation by insect pest. In chilli, sucking pests are a major problem and they can cause 60 to 75% loss in yield. Therefore, a study was undertaken to assess the bioefficacy of some new insecticides (imidacloprid and thiacloprid) against chilli aphid, Aphis gossypii Glover. Six treatments (imiacloprid17.8SL @ 25 and 50 g a.i. ha-1, thiacloprid 21.7SL @ 54 and 108 g a.i. ha-1 and dimethoate 30EC @ 300 and 600 g a.i. ha-1) were applied along with control with the initiation of aphid population consisting three replications. Pre-treatment population of aphids was taken one day before the spray and subsequently observation was recorded on 1, 3, 7, 10 and 14 days after insecticide spray. The dissipation pattern of imidacloprid at 25 g a.i. ha-1 and 50 g a.i. ha-1 and thiacloprid at 54 g a.i. ha-1 and 108 ga.i/ha were also studied by collecting chilli fruits and soil samples at 0, 1, 3, 5, 7, 10and 15 DAS. Immediately after collection of samples extraction was done followed by clean up and analysis using High Performance Liquid Chromatography (HPLC). The bioefficacy study revealed that the overall mean reduction of chilli aphid population was highest in imidacloprid at 50 g a.i. ha-1 with 80.33% reduction. The maximum fruit yield was also recorded in imidacloprid @ 50 g a.i. ha-1 with 86.10 q/ha. Dissipation study revealed that the initial deposit of imidacloprid at 25 and 50 g a.i. ha-1 in fruit samples were 1.20±0.102 and 1.74±0.103 mg/kg respectively which dissipated to BDL on 10th DAS. Half-life values of imidaclorid in chilli were 1.75 and 1.87 days at single and double dose, respectively. A waiting period of 4.52 and 5.84 days were calculated for single and double doses, respectively. In thiacloprid, an initial deposit of 1.10±0.036 and 1.84±0.034 mg/kg was observed on chilli fruits at both recommended dose and double the recommended dose, respectively. The residues were dissipated to BDL on7th DAS. The half-life and waiting period of thiacloprid in chilli at single and double doses were worked out to be 1.44 and 1.46 days and 8.33 and 9.53 days, respectively.