Assessment of insecticide resistance in field populations of spotted pod borer, Maruca vitrata Fabricius on vegetable cowpea

The legume pod borer, Maruca vitrata (Fabricius) is a historic and destructive pest of cowpea the popular tropical legume vegetable which is a sound source of nutrients and proteins. Information collected in recent years showed the reduced susceptibility of M vitrata to the commonly used insecticides. The study on the assessment of insecticide resistance in spotted pod borer on vegetable cowpea against the two widely used chemicals chlorpyriphos and lambda-cyhalothrin was carried outin Department of Agricultural Entomology, College of Agriculture, Vellayani during 2012–2013 at three locations viz field with no previous history of pesticide application (location-I, Venganoor), field where no control failures had been observed (location-II, College of Agriculture, Vellayani) and field with known reported control failures (location-III, Kalliyoor). The study showed that population collected from location-I was found to be susceptible for both the chemicals with resistance ratio 1, population from location-II to be moderately resistant with a resistant ratio of 2.28 and 2.38 and population from location-III to be resistant with resistance ratio of 2.93 and 7.94 for chlorpyriphos and lambda-cyhalothrin respectively.