MSc

The study entitled ‘Evaluation of pongamia oil soap against major pests of vegtable cowpea, Vigna unguiculata subsp. sesquipedalis (L.) Verdcourt’ was aimed at evaluating the efficacy of a new product made of pongamia oil - pongamia oil soap at different concentrations in combating the major pests of vegetable cowpea, viz., pod borers, pod bugs, leaf miner and aphids.

Laboratory bioassay of pongamia oil soap was carried out in the Department of Agricultural Entomology, College of Agriculture, Padannakkad, during 2018- 2019 to evaluate the feeding deterrency and growth retardation properties of pongamia oil soap against fifth instar and first instar larvae of leaf eating caterpillar, Spodoptera litura respectively. The test organisms were exposed to six treatments viz., T1: Pongamia oil soap 0.6%; T2: Pongamia oil soap 1%; T3: Pongamia oil soap 2%; T4: Neem oil soap 0.6%; T5: Soap solution 0.5%; T6: control with three replications under completely randomised design (CRD).

Among the different treatments, pongamia oil soap 2 per cent showed the maximum antifeedent activity which was statistically on par with pongamia oil soap 1 per cent against fifth instar larva of Spodoptera litura. Pongamia oil soap 2 per cent exhibited maximum growth retardation activity which was statistically on par with pongamia oil soap 1 per cent against first instar larvae of S. litura. Spraying of pongamia oil soap 2 per cent showed 100 per cent mortality of aphids Aphis craccivora two hours after the treatment. Pongamia oil soap 1 per cent caused 100 per cent mortality four hours after treatment while neem oil soap 0.6 per cent and pongamia oil soap 0.6 per cent resulted in 100 per cent mortality only twelve hours after treatment.

Field study was carried out using randomised block design (RBD) with seven treatments and four replications on vegetable cowpea variety ‘Vellayani Jyothika’ during rabi and summer seasons at the Instructional farm, College of Agriculture, Padannakkad. The treatments applied were: T1: Pongamia oil soap 0.6%; T2: Pongamia oil soap 1%; T3: Pongamia oil soap 2%; T4: Neem oil soap


0.6 %; T5: Spinosad 45 SC @ 0.5 ml/L of water –Standard check; T6: Soap solution 0.5%; T7: Absolute control. All treatments were applied once at vegetative stage and twice during reproductive stage. Observations were taken one day prior to treatment and 1, 3, 5, 7 and 14 days after treatment (DAT) for sucking pests. Damage symptoms were observed one day prior to and 7 and 14 DAT.

After first spray during rabi and summer seasons, pongamia oil soap 2 per cent was significantly superior among all the treatments in reducing the aphid Aphis craccivora population. The same trend was observed in the case of mean percentage of shoots infested by aphid population. Against pod bugs, pongamia oil soap 2 per cent showed maximum efficacy compared to other treatments after second and third spray during rabi and summer seasons up to seven days and was significantly superior over the control. Damaged pods recorded on seven days after the spray also exhibited similar results. The mean percentage of damaged flowers and pods due to spotted pod borer Maruca vitrata were significantly low in Spinosad 45SC as compared to other treatments including pongamia oil soap 2 per cent. However all the treatments were effective in reducing the sucking pests except soap solution
0.5 per cent. The soap solution 0.5 per cent always was on par with control indicating that soap has no role in the effect of pongamia oil soap. Since the leaf miner attack was negligible in the field during both rabi and summer seasons, it was not recorded.

Pongamia oil soap 2 per cent exhibited increased total yield and marketable yield as compared to that of control due to lower incidence of pests during both the seasons. Economics of pongamia oil soap 2 per cent in terms of cost benefit ratio was also high as compared to control in both rabi and summer seasons, making it an effective component in IPM programmes.