Following the introduction of the pyrethroid insecticides in the late 1970's, it became apparent that resistance to this class of compounds would be eminent because of their extensive use patterns. The Southeastern Untied States, particularly the lower Coastal Plain Region, was thought to be at high risk for resistance because of the large number of applications that were required for control of the heavy insect pest populations. The climate and length of growing season of the southernmost areas of the Southeast provided an additional one to two generations of pests compared to other parts of the Cotton Belt. In addition, the severity of the boll weevil, Anthonomus grandis, prompted even more applications which generally were made with pyrethroids or mixtures of phosphates and pyrethroid materials.

Susceptibility to the pyrethroids have been used in most state is the Southeast for the last several years. These efforts have been made to establish baseline information regarding pyrethroid susceptibility and to track the potential for resistance that has shown up in other parts of the Cotton Belt.

From the data that has been obtained, there currently is no indication that a change in susceptibility to pyrethroids has occurred in tobacco budworm, Heliothis virescens, or bollworm, Helicoverpa zea, populations through this entre region. Topical bioassays indicate similar levels of susceptibility as was found in 1978. We can, thus, say with confidence that these materials are still as effective today as they were in 1977 when they were introduced. Additionally, adult vial bioassays which were made in each of the southeastern states ten microgram/vial dose and very low survival at a rate of one microgram/vial in 1992 (Annual Conference Report, these Proceedings). This is further evidence that we have not as yet developed resistance to pyrethroid insecticides in tobacco budworm. The one exception might be in the northern area of Alabama. In this region the production system, climate, agroecosystem and insecticide use patterns are more similar to that of the Mississippi hill country than the coastal Plain region. There are two possible explanations for the lack of resistance buildup in the Southeast despite the large number of seasonal applications. One, there is a greater diversity of crops and wild hosts for bollworm/tobacco budworm in the Southeastern agroecosystem compared to other areas where resistance has been documented. This provides a reservoir for untreated susceptible individuals since each individual of each generation is not exposed to pyrethroid insecticides. This assists in maintaining a susceptible population. Secondly, and this is highly speculative, if the appearance of resistant individuals is, at least partially, attributed to migration, the Southeast may be isolated from the traditional upper level winds or "storm track" that blows from south Texas through the Mississippi Delta crossing north Alabama. The Appalachian Mountains provides a barrier keeping moths from being carried all the way into North Carolina. The Southeast has thus far been spared the problem associated with pyrethroid resistance in tobacco budworm. We do know that this may only be a temporary budworm. We do know that this may only be a temporary reprieve as resistance may appear at any time. We continue efforts to minimize the use of pyrethroid insecticides except where necessary for bollworm/tobacco budworm control. The successful completion of the Boll Weevil Eradication.

Program in Virginia, North Carolina and South Carolina and the near eradication of the pest in Georgia, Florida and south Alabama has provided the impetus for reduced insecticide input for cotton production. This may forestall the occurrence of pyrethroid resistance is tobacco budworm even more.

Plans are already in place to continue to monitor populations of tobacco budworm as well as bollworm in an effort to detect any shifts in susceptibility at an early stage of development.