Larvae of the corn earworm, Heliothis armigera (HUBNER), ingested a lethal inoculum of Heliothis nuclear polyhedrosis virus (HsNPV) while hatching from virus-treated eggs. Spraying of the virus at dilution of 1/400 on eggs immediately before hatching resulted in 93.6% larval mortality compared with 36.9% on newly laid eggs. The virus remained highly pathogenic to H. armigera larvae, even to larvae introduced into corn ears for the second time at 10 days after viral application. Applications of HsNPV to 1-day-old larvae had better control than to 4-day-old larvae. H. armigera densities were significantly reduced 14 days post application with HsNPV, and the control was better than that with carbofuran. Application of the virus increased from 18.7% to 36.1% ears free of larval damage. The injection of HsNPV preparations into corn ears was more effective than spraying the ears.