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

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%.