Bio-efficacy of Some Newer Insecticides against Brinjal Shoot and Fruit Borer, Leucinodes orbonalis (Guen) and their residues in/on brinjal fruits.
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Date
2013
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Rajendra Agricultural University, Pusa (Samastipur)
Abstract
Bio-efficacy of six newer insecticides – emamectin benzoate (15 g a.i. ha-1), imidacloprid (20 g a.i. ha-1), indoxacarb (50 g a.i. ha-1) lambda – cyhalothrin (15 g a.i. ha-1) and spinosad (50 g a.i. ha-1) along with quinalphos (250 g a.i. ha-1) was evaluated against shoot and fruit borer (Leucinodes orbonalis Guen.) in brinjal (Solanum melongena Linn) at Rajendra Agricultural University, Pusa, Bihar during Rabi 2012-13. Spinosad treatment was significantly superior to others and at par with emamectin benzoate in reducing the shoot and fruit borer damage. Spinosad at 50 g a.i. ha-1 recorded the maximum fruit yield (280.42 q ha-1). It was followed by emamectin benzoate at15 g a.i. ha-1 (267.74 q ha-1) and indoxacarb at 50 g a.i. ha-1 (262.58 q ha-1). Lambda - cyhalothrin 15 g a.i. ha-1 treatment recorded maximum cost - benefit ratio of 1: 4.23 closely followed by imidacloprid 20 g and quinalphos 250 g a.i. ha-1 with ICBR of 1: 3.71 and 1: 3.43, respectively.
Residues of imidacloprid at 20 g a.i. ha-1 and lambda – cyhalothrin at 15 g a.i. ha-1 were estimated quantitatively by HPLC/GLC in/on brinjal fruits. Initial deposits of insecticides were higher in imidacloprid than lambda – cyhalothrin. Initial deposits of 0.652 mg kg-1 of imidacloprid dissipated to 93.17 per cent on 10th day. In lambda – cyhalothrin the initial deposits were 0.138 mg kg-1 which dissipated to 92.75 per cent on 10th day. The degradation of imidacloprid was relatively higher as compared to lambda – cyhalothrin. Both imidacloprid and lambda – cyhalothrin had half – life values of 1.92 and 2.65 days, respectively on brinjal fruits. The safe waiting period for imidacloprid was found 4.70 days. In lambda - cyhalothrin, no waiting period is required after its application as the initial deposits were less than its MRL (0.3 mg kg-1). Simple washing of treated brinjal fruits with tap water removed insecticide residue in significant amount. The per cent removal of insecticide residues were to the extent of 25.23 – 36.20 per cent in imidacloprid and in lambda – cyhalothrin, the reduction in residue was 28.57 – 42.75 per cent.
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