Effects of natural sunlight and moisture on the efficacy of Steinernema carpocapsae nematodes in controlling Trichoplusia ni and Agrotis ipsilon

The ability of Steinernema carpocapsae to survive environmental conditions and combat insect pests was tested.;The exposure of nematodes to direct sunlight and to less moist conditions decreased their efficacy. The longer nematodes had been exposed to sunlight, the less effective they were in entering and killing Trichoplusia larvae. Larval mortality caused by nematodes ranged from 100% to zero after the nematodes had been exposed to the sun for periods of 4 minutes to 192 minutes. Nematodes caused 83.3% to 85% mortality of Trichoplusia larvae when optimum moisture was present, whereas no mortality was obtained when moisture was essentially absent. Nematodes applied to moist soil caused 100% mortality of Agrotis larvae, and 40% to 48% control in dry soil. Application of nematodes in late afternoon sunshine resulted in better control of Agrotis larvae (88% to 92%) than applications during sunnier morning exposures (20% to 28%).