PhD

The investigation on the “Efficacy and biosafety of new generation insecticides for the management of fruit borers of cowpea, brinjal and okra” was conducted at the College of Agriculture, Vellayani, during 2010-2013. The objectives were to evaluate the efficacy of new generation insecticides against the fruit borers of cowpea, brinjal and okra, assess their safety to entomopathogenic fungi, determine their persistence and degradation and standardize methods to decontaminate the residues on the fruits. The studies were conducted with eight new generation insecticides viz., emamectin benzoate 5SG @10 g a.i. ha-1, spinosad 45 SC @ 75 g a.i. ha-1, novaluron 10 EC @ 100 g a.i. ha-1, chlorantraniliprole 18.5 SC @ 30 g a.i. ha-1, indoxacarb 14.5 SC @ 60 g a.i. ha-1, fipronil 80 WG @ 50 g a.i. ha-1, thiodicarb 75 WP @ 750 g a.i. ha-1 and flubendiamide 480 SC @ 100 g a.i. ha-1 . Two conventional insecticides (carbaryl 50 WP @ 750 g a.i. ha-1 and malathion 50 EC @ 500 g a.i. ha-1) and an untreated control were maintained as check.
Laboratory screening of the insecticidesagainst Maruca vitrata, Leucinodes orbonalis and Earias vitella, indicated high mortality of the pests one and three days after treatment with a subsequent decline in the mortality. The insecticides were on par in their efficacy.
All the new generation insecticides reduced the pest infestation on the vegetables significantly in the field. The reduction in the flower and pod damages in cowpea ranged from 53.97 to 76.86 and 63.69 to 84.82 per cent, respectively. Damages to brinjal and okra fruits were reduced by 45.96 to 72.21 per cent and 44.34 to 83.26 per cent, respectively. Chlorantraniliprole, indoxacarb and emamectin benzoate which recorded more than 70 and 80 per cent reduction in flower and pod damages in cowpea, chlorantraniliprole, indoxacarb, emamectin benzoate and flubendiamide with more than 60 per cent reduction in fruit damage in brinjal, and chlorantraniliprole, flubendiamide and indoxacarb with more than 70 per cent reduction in fruit damage in okra were superior. The yield was also significantly high in these treatments in the three crops. Prophylactic sprays with neem seed kernel extract 5 % at flower bud initiation and after a fortnight, decreased the population of the pod borer of cowpea remarkably. Subsequently, one spray of the insecticides sufficed to check the pest.
All the insecticides were compatible with Beauveria bassiana and Metarrhiziumanisopliae. Flubendiamide and carbaryl inhibited the growth of Lecanicillium lecanii.
Chlorantraniliprole with a waiting period of one day in all the three vegetables was the safest insecticide. The other insecticides with waiting periodswithin the harvest intervals of the crops were spinosad (1day), emamectin benzoate (3 days) and flubendiamide (3 days) in cowpea, indoxacarb (1day), spinosad (1day) and emamectin benzoate (4 days) in brinjal and indoxacarb (2 days) and thiodicarb (2 days) in okra.
Immersing insecticide treated fruits in slaked lime 2%, turmeric 1 %, vinegar 2% or tamarind 2% solution for twenty minutes followed by washing in water and scrubbing which removed more than 60 per cent residues of most of the insecticides were the effective decontaminating methods for the new generation insecticides.
Considering the efficacy of the insecticides against the pests, associated yield increase, benefit cost ratio of the insecticide treatments, waiting period and compatibility with bio agents, chlorantraniliprole 18.5 SC @ 30 g a.i. ha-1, indoxacarb 14.5 SC @ 60 g a.i. ha-1 and emamectin benzoate 5SG @10 g a.i. ha-1 were adjudged as the potential insecticides against the fruit borers of cowpea, brinjal and okra.