Isolation, Characterization and efficacy entomopathogenic nematodes as biological control agents against Asian corn borer (Ostrinia furnicalis Guenee) (Lepidoptera: Pyralidae) and cutworm (Spodoptera litura Fabricius) (Lepidoptera: Noctuidae)

Entomopathogenic nematodes were isolated from soil samples collected from Los Banos, Laguna, Lipa, Batangas, and Infanta, Quezon [Philippines]. Based on morphological examination using photomicroscopy and scanning electron microscopy, the identified nematodes belong to family Steneirnemetidae. These nematodes were cultured and mass produced successfully on dry dog food on agar. Based on 2000 infective juveniles (IJs)/mL, the most virulent nematode was the strain from Los Banos, causing 50% and 90% mortality of Asian corn borer (ACB) and cutworm, respectively, after 96 hours exposure. Additional assays of the entomopathogenic nematode on different larval instars of the two insect species gave LC sub50's ranging from 5,623.13 to 8,000 IJs/mL for ACB and 1,068.35 to 1,675.70 IJs/mL for cutworm after 48 hours exposure. The LC sub50 values indicate that cutworm larvae were more susceptible than the ACB larvae to the entomopathogenic nematode. The ne matode penetrated into the cutworm larvae body through the anus. Highest concentration of nematodes was found in the body cavity beneath the hindgut and the midgut. Based on decreasing number of individuals, the order is as follows: Body cavity beneath the hindgut greater Body cavity beneath the midgut greater hindgut greater midgut greater hindgut greater midgut greater foregut. In the screen house test, potted sweet corn plants infested with ACB larvae was sprayed with nematode suspension at the rates of 2000, 4000 and 8000 IJs/mL. The result showed significantly higher ACB mortality compared with the control, but significantly lower ACB mortality compared with the insecticide deltamethrin. On the otherhand, potted sweet corn plants infested with cutworm larvae sprayed with nematode suspension at the rates of 1000, 1500, and 2000 IJs/mL showe significantly higher cutworm mortality compared with the control, but significantly lower cutworm mortality compared with the insect icide deltamethrin. Based from the results of this study, the Los Banos enthomopathogenic nematode isolate is a promising biological control agent against larvae ACB and cutworm.