In 1965 cotton was planted in northern Tamaulipas, Mexico in 162,000 ha (400,000 acres) but it declined to 810 ha (2000 acres) by 1990 because of costs for insect control, lint price and cotton root rot. In 1965 the delegation of Sanidad Vegetal in Matamoros (personal communication) established that bollworm, Helicoverpa zea (Boddie) larval populations predominated early in the growing season while the tobacco budworm, Heliothis virescens (F.), and flowering predominated by the end of May and June.

In 1990 and 1991 larval populations of tobacco budworm were greater than larval populations of bollworm early in the growing season. Thereafter larvae of bollworm predominated until the end of the cotton season. This is the opposite the results in 1965. Larval parasitism was evident in 1990 and 1991 in June and ranged from 14% to 50%. In 1991, no resistance to methyl parathion and permethrin was shown by the bollworm and tobacco budworm.