Influence of host plants on the susceptibility of tobacco caterpillar, Spodoptera litura (Fab.) to certain insecticides

摘要

Tobacco caterpillar, Spodoptera litura (Fab.) (Lepidoptera: Noctuidae) is a polyphagous insect pest of national importance causing economic damage to a number of agricultural crops. It is known to damage more than 50 crops viz., tobacco, cole crops, castor, cotton, sunflower, chilli, etc. (Murthy et al., 2007). Several synthetic insecticides were tested and recommended to control this pest. However, indiscriminate and frequent application of these chemicals resulted in problems like build up of resistance, secondary pest resurgence and environmental pollution. In recent years, there are reports of S. litura developing resistance to recommended doses of several insecticides (Navatha and Murthy, 2006). In the southern parts of India, it is reported tohave developed resistance virtually to all commonly used insecticides such as cypermethrin, fenvalerate, endosulfan, quinalphos and monocrotophos (Armes et al., 1997). These developments necessitate a relook at the dosages recommended by taking into account the crop on which the pest has to be managed. Variable efficacy of insecticides against S. litura larvae grown on different host plants may be related to the secondary metabolites, enzymes, and pH of host plants. Significant findings have been reported by Kulkarni and Lingappa (2001), Santiago et al. (2005) and Massarat (2007) reported on the influence of host plants on susceptibility of insects to different insecticides. This insect being polyphagous in nature, it was considered desirable to studythe influence of some of the important host plants on its susceptibility to some newer insecticide molecules. So, this additional information would make existing IPM programmes more effective and sustainable, while decreasing the adverse effect on the crop and associated environment.