Insecticidal products may fail to work in the field for many reasons, and resistance should only be suspected when all others have been eliminated. Even when the pest population is known to contain a proportion of resistant individuals, the products may work perfectly well unless the actual numbers of resistant individuals are high. Pyrethroid resistant Heliothis appeared in a number of areas around the world. The first documented case was in 1983 in Australia, where a resistance management strategy was put in place and appears to have succeeded in handling the problem. Pyrethroid-involved parties are now working together to combat this threat and we have grounds for optimism.

In this talk I will concentrate on resistance to pyrethroids in Heliothis species, and after describing events in other parts of the world I will try to relate these experiences to the current problem facing the US cotton industry: the imminent danger of resistance in Heliothis vireacens, the tobacco budworm.