Efficacy of entomopathogenic nematodes against the cabbage butterfly (Pieris brassicae (L.) (Lepidoptera: Pieridae) infesting cabbage under field conditions

Abstract

Experiments were conducted to test the pathogenicity of entomopathogenic nematode, Heterorhabditis pakistanensis alone and in combination with the chemical insecticides, viz., Dichlorvos and Quinalphos and Neem product, viz., Azadirachtin against the cabbage butterfly, Pieris brassicae (L.) (Lepidoptera: Pieridae) infesting cabbage plants under laboratory and field conditions. In laboratory test, inoculum level of 200 infective juveniles (IJs) was most effective causing mortality to both 3rd and 4th instars larvae at 48 h. Nematode multiplication rate in insect cadaver was inversely proportional to the size of initial inoculum level of IJs, whereas IJs yield was directly proportional to the size of larva. The 4th instar larva resulted in a highest yield of IJs, followed by 3rd, 2nd, and 1st instars larvae at all the inoculum levels used in the study. IJs were found compatible with the chemical insecticides and Neem product at lower than half of the optimum single dose. The cumulative mean survival percentage of IJs recorded the highest (77.5%) in the combination of 100 IJs + Azadirachtin (0.25%) and lowest (70.6%) in 100 IJs + Dichlorvos 76 EC (0.05%). Under field conditions, H. pakistanensis (3.0 lakh IJs/m2) + Dichlorvos 76 EC (0.025%) resulted to the highest larval mortality (79.65%), followed by H. pakistanensis (3.0 lakh IJs/m2) + Azadirachtin (0.25%), where it was 76.22%. The larval mortality was the least (61.16%) in case of H. pakistanensis (3.0 lakh IJs/m2) when applied alone. H. pakistanensis + Dichlorvos resulted to the highest increase (31.42%) in cabbage yield over untreated control.