Eco-friendly management of major pests of yard long bean, vigna unguiculata subsp. sesquipedalis (L.) Verdcourt.

Abstract

The study entitled ′′Eco-friendly management of major pests of yard long bean, Vigna unguiculata subsp. sesquipedalis (L.) Verdcourt′′ was carried out in the Instructional farm of College of Agriculture, Padannakkad, Kasaragod during two seasons viz., kharif (May to August) and rabi (September to December) in the year 2016. The vegetable cowpea variety ‘Lola’ released by KAU was selected for the study. The study was undertaken with an intention to find out the efficacy of different microbial agents, neem based and biorational insecticides. The experimental design was RBD with 9 treatments and three replications. The treatments included; T1- Beauveria bassiana (liquid formulation @ 107 spores/ml of water), T2- Metarhizium anisopliae (liquid formulation @ 107 spores/ml of water), T3- Lecanicillium lecanii (liquid formulation @ 107 spores/ml of water), T4- Bt formulation 2× 108 cfu/ml @ 1 ml/l of water, T5- Neem based insecticide (Azadirachtin 1 per cent @ 5 ml/l of water), T6- Neem oil emulsion 5 per cent (50 ml/l of water), T7- Spinosad 45 SC @ 0.4 ml/l of water, T8- Malathion 50 EC @ 2ml/l of water (standard check), T9- Absolute control. All the treatments were imposed at fortnightly intervals just after the initial attack of pest was seen and observations were recorded at weekly intervals corresponding to standard weeks. The data were subjected to square root transformation and analyzed using ANOVA. After three consecutive sprays of Spinosad 45 SC @ 0.4 ml/l of water at fortnightly intervals there was complete reduction of pod borer larvae during kharif and rabi season. The percentage of flowers and pods infested by pod borer larvae were also reduced completely and no infestation was noticed after three consecutive sprays of Spinosad during both seasons. Thus it was found that Spinosad 45 SC was effective in reducing the number of pod borers, percentage of flowers infested and percentage of pods infested. During kharif season, Beauveria bassiana was found to be the most effective treatment in reducing the nymphs and adults of pod bugs with minimum number of 0.56 bugs per plant followed by 0.63 bugs in T5 compared to T9 with 7.46 bugs per plant after three consecutive sprays. During rabi season, Azadirachtin 1 per cent showed no incidence of pod bugs after three sprays and Neem oil 5 per cent consistently reduced number of bugs to zero on 15 days after third spray whereas T9 exhibited maximum number of 4.26 bugs/plant. The effect of Beauveria bassiana was lowered during rabi season. It might be due to the inability of Beauveria spores to germinate and cause infection during that season because of inadequate humidity. Azadirachtin 1 per cent incessantly lowered the per cent of pods infested by pod bugs to zero even after two sprays during both seasons and leaf miner attacked leaves was also found minimum in plot treated with Azadirachtin 1 per cent (0.63 leaves/plant) compared to T9 (7.12 leaves/plant). The aphid population on shoots and per cent of aphid infestation on shoots were found to be zero after three consecutive sprays of Lecanicillium lecanii at fortnightly intervals during kharif season. Lecanicillium lecanii also lowered the aphid population on pods and caused exorbitant reduction in the percentage of infested pods during both seasons after three sprays. Though pod length is an inheriting character, maximum length of 42.30cm and 48.40cm was shown by T7 during kharif and rabi seasons respectively. During both seasons viz., kharif and rabi, the total and marketable yield was high in T7 with highest benefit – cost ratio of 1.50 and 2.26 respectively.