Cotton pests, pyrethroid resistance

Cotton is one of the crops most heavily reliant upon insecticide use. Although Bt cotton has been introduced in some areas, insecticide sprays remain as important components of cotton pest management programs. In some areas of the cotton belt, the majority of applications are made by aircraft. Issues which have been of regulatory concern in recent years include pest resistance associated with the frequent sprays, beneficial insect effects, worker exposure, and spray drift impacts on surfrice water quality. Products currently in use include organophosphates such as azinphos-methyl, methyl parathion, acephate, and disulfoton, pyrethroids such as lambda-cyhalodirin and carbamates such as methomyl. 

The magnitude of the present annual resistance monitoring effort on the part of the PEG-US group, as well as state and federal researchers, is unprecedented as far as field crop pests are concerned and reflects the serious concern within the cotton industry that pyrethroid resistance could get out of control. These monitoring efforts have shown a general trend in some areas to increased tolerance of tobacco budworms to pyrethroids, as well as an expansion of the geographical area within which such increased tolerance has been detected. However, except for the aforementioned incidents there have been no documented failures in field control. 

Turkey. The second case of pyrethroid resistance in 1984 was in Turkey. In 1985 and 1986, PEG sponsored studies which confirmed the presence of resistance in fl. armigera. The Turkish form of resistance management involved the implementation of a ban on the importation of pyrethroids for their use on cotton pests (21) -... 

The continuing use of pyrethroids in agriculture has led to the emergence of resistant strains of pests. One of the best-studied examples is the tobacco budworm (Heliothis virescens), a very serious pest of cotton in the southern United States (McCaffery... 

A case in point is the unraveling of resistance to methyl parathion in the tobacco budworm, Heliothis virescens, which is a major pest of cotton as well as tobacco. In South Carolina, there is very severe, stable resistance. Although pyrethroid insecticides are very effective and there is no resistance to them in South Carolina at this time, it would be very useful to understand the genetic basis of methyl parathion resistance in case resistance to pyrethroids should arise in the future or spread eastward from Texas where it has been detected. Recent investigations with this pest will be described to illustrate certain mechanisms. 

The two Heliothis species that have most commonly developed resistance are Heliothis virescens and armigera. The loss of the organophosphorous insecticides (OP s) to resistance in the 1970 s literally pushed the synthetic pyrethroids into the marketplace. Since their introduction in 1978, it was clear that these highly cost effective and environmentally compatible insecticides would be heavily relied upon to replace the OP s. The synthetic pyrethroids have become the most widely used chemicals for the control of insect pests on cotton, representing about 48% of all the insecticides applied worldwide ( ). Most applications are directed toward controlling Heliothis spp. 

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