In recent field tests on okra, tobacco, potato and sugar beets in Pakistan, a granulosis virus(AsGV) of the cutworm (Agrotis segetum) from Denmark proved as effective as Bt and the chemical insecticides dieldrin and tamaran in reducing damage by cutworm larvae, by up to 85%. The virus has demonstrated field efficacy in Denmark, Sweden, Pakistan, and the USSR, and is viewed as a biological replacement for the persistent chlorinated hydrocarbon insecticides whose use is being abandoned around the world.

Trials tested one to three AsGV treatments. Two treatments five days apart were optimal, reducing naturally occurring field populations of cutworm larvae by 64 to 85% over two years of trials. Best control with AsGV, as well as chemicals, is obtained against early instar larvae. Late instars have low susceptibility to both AsGV and chemicals. Superior results came when light traps were used to time treatments and determine when the cutworm moths were flying. Pheromone traps were not tested, but the authors feel that they may also prove useful in timing treatments. It was also reported that partially purified AsGV without activated charcoal was as effective as highly purified AsGV with activated charcoal; the researchers believe that insect tissue fluids protect the virus from ultraviolet light.

Zethner, O. et al. 1987. Entomophaga 32 (5): 449-455

For more information:

Dr. O. Zethner
Development Cooperation Bureau
Royal Veterinary and Agricultural University
>Copenhagen, DENMARK