Eco-friendly approaches for the management of defoliators on onion

Onion (Allium cepa L.) is the important member of the family Amaryllidaceae (Alliaceae) and widely grown herbaceous biennial vegetable crop. Insect pests and diseases are the major constraints in production and productivity of Onion. The tobacco caterpillar, Spodoptera litura (F) is one of the most important insect pests of onion in the Asian tropics. In recent years, farmer's income is declining particularly due to the rising costs of inputs in plant protection. An experiment was carried out at Main Agricultural Research station, Raichur during September 2010 and 2011 in a Randomized Block Design having a plot size of 6.0 m² area. Bio-efficacy of 11 treatments comprising of organic and chemical treatments were evaluated. Rynaxypyr 18.5% SC was found to be best treatment which recorded 1.18, 0.56, 0.66 and 0.86 Spodoptera larvae per plant at 1, 3, 7 and 14 DAS, respectively. At 3 DAS lufenuron and spinosad 45% SC found to be on par with each other as it recorded 1.2 and 1.3 Spodoptera larvae per plant, respectively. At 7 and 14 DAS rynaxypyr 18.5% SC stood first and was followed by novaluron 10% EC in reducing pest population (1.2 and 1.3 Spodoptera larvae per plant, respectively). In second season also similar trend was noticed. With respect to yield, novaluron 10% EC recorded highest yield of 23.30 t/ha. followed by lufenuron 5% EC (22.6 t/ha) which was on par with spinosad 45% SC which recorded 22.50 t/ha. All the insecticidal treatments recorded increase in marketable yield over untreated check. The cost benefit ratio calculated on the basis of cost of protection for different insecticidal treatments revealed that rynaxypyr 18.5% SC was found superior as it recorded net returns of Rs. 1, 10, 088/-with B: C ratio of 4.08, followed by spinosad 45% SC which recorded net returns of Rs. 1, 08, 892/-with B: C ratio of 4.07.