MSc

A study on “Insecticide mixtures for the management of pest complex in cowpea” was undertaken in College of Agriculture, Vellayani and in the farmers field at Kalliyoor during 2016 to 2018. The main objectives were to evaluate the efficacy of insecticide mixtures having component molecules of different mode of action against pests of cowpea and to study the dissipation pattern of mixtures in cowpea pods. Major pests documented in the experimental field were sucking pests viz., pod bug, Riptortus pedestris Fabricius, cowpea aphid, Aphis craccivora Koch, spotted pod borer, Maruca vitrata Fabricius, and leaf eating caterpillar, Spodoptera litura Fabricius.
Experiment was laid out in RBD to study the efficacy of insecticide mixtures viz., chlorantraniliprole 8.8 % + thiamethoxam 17.5 % SC @ 150 g a.i ha-1, lambda cyhalothrin 4.6 % + chlorantraniliprole 9.3 % ZC @ 30 g a.i ha-1, thiamethoxam 12.6 % + lambda cyhalothrin 9.5 % ZC @ 27.5 g a.i ha-1, beta cyfluthrin 8.49 % + imidacloprid 19.81 % SC 15.75+36.7 g a.i ha-1, flubendiamide 19.92 % + thiacloprid 19.92 % SC @ 48+48 g a.i ha-1, chlorantraniliprole 18.5 % SC +thiamethoxam 25 % WG (hand mixed) @ 1:1 @ 0.30 mL L-1 along with standard checks chlorantraniliprole 18.5 % SC @ 30 g a.i ha-1 and thiamethoxam 25 % WG @ 0.30 g L-1 against cowpea pests (Cowpea variety- Vellayani Jyothika).
The results of the study revealed that chlorantraniliprole 8.8 % + thiamethoxam 17.5 % SC @ 150 g a.i ha-1 was found effective in managing the population of pod bug, R. pedestris, followed by followed by followed by followed by followed by thiamethoxam 12.6 % + lambda cyhalothrin 9.5 % ZC @ 27.5 g a.i ha-1 and beta cyfluthrin 8.49 % + imidacloprid 19.81 % SC @ 15.75+36.7 g a.i ha-1. Less incidence of bug was found in effective treatments after 7 days of spraying. More or less similar result was obtained in the management of cowpea aphid, A. craccivora. Less number of aphid was observed in the plants treated with chlorantraniliprole 8.8 % + thiamethoxam 17.5 % SC @ 150 g a.i ha-1, thiamethoxam 12.6 % + lambda cyhalothrin 9.5 % ZC @ 27.5 g a.i ha-1, chlorantraniliprole 18.5 % SC + thiamethoxam 25 % WG (hand mixed) @
1:1 @ 0.30 mL L-1 and thiamethoxam 25 % WG @ 30 g a.i ha-1 against 211.67 aphids plant-1 in control after 15 days of spraying. Significantly higher reduction in leaf damage by S. litura was recorded in plants treated with lambda cyhalothrin 4.6 % + chlorantraniliprole 9.3 % ZC @ 30 g a.i ha-1 (25.03) which was on par with thiamethoxam 12.6 % + lambda cyhalothrin 9.5 % ZC @ 27.5 g a.i ha-1 (26.46) and chlorantraniliprole 8.8 % + thiamethoxam 17.5 % SC @ 150 g a.i ha-1 (30.20) 10 days after spraying. Whereas, in the management of cowpea pod borer, M. vitrata, less incidence of larvae was found in lambda cyhalothrin 4.6 % + chlorantraniliprole 9.3 % ZC @ 30 g a.i ha-1 and chlorantraniliprole 8.8 % + thiamethoxam 17.5 % SC @ 150 g a.i ha-1 treated plants after 5 days of spraying against 6.67 larvae in control.
Dissipation of residues of these effective insecticide mixtures were studied by analysing the pods collected at 0, 1, 3, 5, 7, 10 and 15 days after treatment and the result showed that both the single insecticides in chlorantraniliprole 8.8 % + thiamethoxam 17.5 % SC were dissipated within ten days with half-lives of 5.34 and 3.01 respectively and in lambda cyhalothrin 4.6 % + chlorantraniliprole 9.3 % ZC, lambda cyhalothrin dissipated in five days and chlorantraniliprole dissipated in seven days with half-lives of 5.58 and 13.67 days respectively. The infestation of sucking pests, borers and leaf feeders simultaneously occur in cowpea especially in pod bearing stage. The results of the study revealed that spraying chlorantraniliprole 8.8 % + thiamethoxam 17.5 % SC @ 150 g a.i ha-1, thiamethoxam 12.6 % + lambda cyhalothrin 9.5 % ZC @ 27.5 g a.i ha-1 and lambda cyhalothrin 4.6 % + chlorantraniliprole 9.3 % ZC @ 30 g a.i ha-1 could effectively manage pest complex in cowpea with minimal or no risk to the consumers.