Field efficacy of the entomopathogenic nematode Steinernema thermophilum Ganguly and Singh (Rhabditida: Steinernematidae) against diamondback moth (Plutella xylostella L.) infesting cabbage

Abstract Tests on field efficacy of Steinernema thermophilum against diamondback moth (DBM) ( Plutella xylostella ) infesting cabbage were conducted between 2002 and 2004. Cabbage plants were inoculated with 10 DBM larvae/plant and then sprayed with S. thermophilum infective juveniles (IJs) at one of three concentrations (1000, 2000 or 3000 IJs/ml). We included an insecticide (Lambda Cyahalothrin at 0.0025%) and a 0 nematode treatment as controls. The average of two years showed that S. thermophilum at 3000 IJs/ml caused the highest mortality of 46%, whereas at 2000 IJs/ml and the insecticide treatment caused 40.5 and 40% mortality in DBM larvae, respectively. The difference among the treatments was non-significant. DBM mortality in the treatments showed a slight increase with increasing temperatures between years. The infectivity of IJs on DBM larvae increased with increasing IJ concentration. The IJs treatments reduced the crop damage by 9.7 to 43.1%, whereas in the insecticide treatment, the reduction was 49.5%.