In-vitro Study on the Efficacy of Entomopathogenic Nematodes (Heterorhabditidae and Steinernematidae) for the Control of the Indian Cabbage White, Pieris canidia

Pieris canidia is one of the serious pests of cruciferous crops causing extensive damage to agricultural crops. Entomopathogenic nematodes (EPNs) therefore represent ideal candidates for biological control of the pest. In this study, the efficacy of four indigenous EPNs species, Heterorhabditis indica, Heterorhabditis baujardi, Steinernema sangi, and Steinernema surkhetense from Mizoram was evaluated against P. canidia under laboratory condition. Different concentrations of nematodes, 10, 25, 50, 100, and 200 infective juveniles per larva (IJs/larva) were used to evaluate larval mortality rate, host penetration rate, and progeny production in insect cadaver. All the four EPN species showed high pathogenicity against the pest for different nematode concentrations and observation periods. At a concentration of 200 IJs/larva, cent percent mortality of the pest was recorded at 72 hr post-incubation for S. surkhetense, 96 hr for S. sangi and H. indica, and 120 hr post-incubation for H. baujardi. Based on the values of LC50 and LT50, H. indica was the most pathogenic among the four nematode species while S. sangi was the least pathogenic. After 24 hr of incubation, the LC50 values of H. indica, H. baujardi, S. surkhetense, and S. sangi were 88.60, 98.29, 113.26 and 95.61 IJs/larva, respectively. At 10 IJs/larva, the LT50 values of H. indica, H. baujardi, S. sangi, and S. surkhetense were 88.12, 90.69, 88.102.30, and 88.11 hr, respectively. The study also disclosed that all the four EPN species successfully infect the pest and showed high rate of penetration into the host. Furthermore, all the nematode isolates were capable of producing large numbers of IJs in larval cadaver of P. canidia that significantly varies between the EPN species. The isolate H. baujardi produced the highest number of IJs followed by H. indica, S. surkhetense, and S. sangi. Our findings therefore reveal that all the four EPN isolates have the potential to be developed as biological control agents for P. canidia.