D3467: Efficacy of entomopathogenic nematodes against Helicoverpa zea and Chrysodeixis includens in the laboratory

Ten strains of entomopathogenic nematodes (EPNs) were tested for virulence against eggs, 1^st to 4^th instars, 5^th instars, and pupae of corn earworm (Helicoverpa zea) and soybean looper (Chrysodeixis includens) in the laboratory. They were Heterorhabditis bacteriophora (HP88 and VS strains), H. floridensis (K22strain), H. georgiana (Kesha strain), Steinernema carpocapsae (All and Cxrd strains), S. feltiae (SN strain), S. rarum (17c+e strain), and S. riobrave (355 and 7-12 strains). The EPN dose was 100 IJs in 1 mL per Petri dish per larva/pupa or ten eggs. Although the infection of EPNs to the eggs of H. zea and C. includens was low (0.00% to 16.67%), all ten EPNs could potentially infect the eggs of H. zea or C. includens, which could also kill the larvae before hatching. Ten strains of EPNs killed 100% of 1^st to 4^th instars H. zeawhile they killed 33%-100% 1^st to 4^th instars C. includens within one week. Ten strains of EPNs killed 30%-90% 5^th instar H. zea and 43.3%-100% 5^th instar C. includens before they turned into pupae. However, there was no significant difference in the mortality for the pupae of H. zea, ranging from 6.67% to 33.33%. As for the pupae of C. includens, the mortality ranged from 6.67% to 63.33%, with four strains of EPNs that did not differ significantly from the control. At the same time, the remaining six showed significantly higher mortality than the control.