Agrotechnology

Bio-efficacy and residue dynamics of insecticides against Plutella xylostella (L.) in cabbage (Brassica oleracea var.capitata)

2^nd International Conference on Agricultural & Horticultural Sciences

Radisson Blu Plaza Hotel, Hyderabad, India February 03-05, 2014

Anugu Anil Reddy

Accepted Abstracts: Agrotechnol

Abstract:

A field experiment was carried out during kharif , 2012 at Students Farm, College of Agriculture, Rajendranagar, Hyderabad wherein the efficacy of seven insecticides viz., emamectin benzoate 5 SG at 11 g a.i.ha -1 , emamectin benzoate 5 SG at 22 g a.i.ha -1 , profenophos 50 EC at 500 g a.i.ha -1 , profenophos 50 EC at 1000 g a.i.ha -1 , spinosad 45 SC at 100 g a.i.ha -1 , bifenthrin 10 EC at 100 g a.i.ha -1 and Bacillus thuringiensis at 5 WP at 25 g a.i.ha -1 were evaluated against Plutella xylostella on cabbage. The dissipation pattern of profenophos 50 EC (1000 g a.i.ha -1 ) and bifenthrin 10 EC (100 g a.i.ha -1 ) was studied collecting samples at regular intervals i.e., 0, 1, 3, 5, 7, 10, 15 and 20 days after last spray and analyzed at AINP on Pesticide Residues, Rajendranagar, Hyderabad to know the dynamics of degradation. Another set of cabbage samples collected at regular intervals i.e., 0, 5, 10, 15 and 20 days after last spray and analyzed for profenophos and bifenthrin residues after removing top three layers to know the effect of pre harvest risk mitigation method and removal of profenophos and bifenthrin residues by using validated QuEChERS method. Among all the insecticides, profenophos (1000 g a.i.ha -1 ) was found to be the most effective one with a maximum reduction in Plutella xylostella population (70.20%), followed by bifenthrin 10 EC at 100 g a.i.ha -1 (68.18%). The initial deposits of 0.99 mg kg -1 profenophos recorded at 2 hours after last spray dissipated to 0.85, 0.82, 0.16 and 0.07 mg kg -1 by 1, 3, 5 and 7 days after last spray, respectively and below determination level (BDL) by 10 th day. Based on the dissipation pattern, a safe waiting period of 15 days was recommended taking into consideration of profenophos MRL (0.01 mg kg -1 ) given by EU. The initial deposits of 2.24 mg kg -1 bifenthrin recorded at 2 hours after last spray dissipated to 1.72, 1.38, 0.82 and 0.23 mg kg -1 by 1, 3, 5 and 7 days after last spray, respectively and below determination level (BDL) by 10 th day. Based on the dissipation pattern, a safe waiting period of 2 days was recommended taking into consideration of MRL (1.0 mg kg -1 ) given by EU and 3 days was recommended based on the MRL (0.4 mg kg -1 ) of CAC. The data collected on removal of profenophos and bifenthrin residues in cabbage by removing top three leaves indicate that 91.91 % of profenophos residues and 25.90 % of bifenthrin residues can be eliminated easily.