Field persistence of the HearNPV (PAU-1 Strain) against Helicoverpa armigera (Hubner) on tomato.

摘要

A direct relationship between sunshine exposure period and loss in original activity remaining (OAR) of foliar deposits of the HearNPV (PAU-1 Strain), when sprayed on the tomato (cv. Punjab Chhuhara) plants @ 109 occlusion bodies per ml, before sunrise, was observed by feeding periodically sampled foliar deposits to Helicoverpa armigera (Hubner) larvae (1.3+or-0.1 cm and 35+or-2.4 mg) in laboratory bioassay study. The LT50 varied between 132 and 264 hr at 4 and 132 hr sunshine exposures respectively, in contrast to 120 h only for unexposed virus (0 h). An initial loss of 5, 20 and 30 per cent in OAR intact was quite rapid at respective sunshine exposures of 4, 8 and 12 h only. Subsequent loss of 35 to 90 per cent in OAR intact was observed rather slowly within 24 to 156 h progressive exposures to the sunshine respectively. However, virus persisted on tomato foliage for 7 days with 10 percent OAR under Ludhiana conditions..