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Boll weevil eradication effort

During the past four years Mississippi cotton growers have made great progress toward their goal of eradicating the boll weevil. Evidence of this progress can be seen readily by examining the historical data on yield losses to boll weevils (Figure 1). Before boll weevil eradication efforts began, statewide yield losses to this pest usually ranged from 2 to 4 percent. While yield losses to weevil were often drastically reduced in years following unusually severe winters, like 1983-84 and 1989-90, the boll weevil recovered quickly, and yield losses of more than 5 percent were sustained in the Hill Region of the state following milder winters (Figure 2).

Last year, boll weevils caused no yield loss to Mississippi cotton. This is a major mile stone in the boll weevil eradication effort. However, this is certainly not an indication that the job of eradicating the weevil is finished. As of last fall, pheromone trap captures indicated that low numbers of boll weevils remained in most cotton producing counties. While these numbers were too low to cause yield loss, past experience has shown that the boll weevil can recover very quickly, if growers relent in their efforts to eliminate this pest from the state.

The excellent progress that Mississippi cotton growers have made in their eradication effort is especially noteworthy when one considers the unusual challenges that boll weevil eradication has faced in Mississippi. Since eradication efforts began in the Hill Region of the state in 1997, Mississippi experienced three consecutive winters that were unusually mild. Such mild winters are favorable to survival of overwintering boll weevils, and this meant the eradication effort received no help from nature during the early years. Fortunately, the winter of 2000-2001 was much colder, and it is anticipated that this will benefit the eradication effort considerably. However, the severity of this past winter fell short of that of 1983-84.

One of the greatest challenges faced by Mississippi's boll weevil eradication effort has been the availability of Bt cotton and the fact that, since eradication efforts began, most fields have been planted to Bt varieties. Overall, Bt cotton has been a huge boon to cotton growers involved in boll weevil eradication, because growing Bt varieties greatly reduces the risk of caterpillar outbreaks that can occur during the early years of eradication efforts. However, in one respect, the widespread planting of Bt cotton complicated eradication efforts.

Historically, when growers applied caterpillar treatments to non-Bt fields they often used insecticides that also were active against boll weevils. This coincidental boll weevil control was a great supplement to boll weevil eradication programs that were conducted before the introduction of Bt cotton. However, Bt fields require fewer treatments for caterpillar pests and this means less coincidental control of boll weevils by grower applied sprays. Essentially this has meant that Mississippi's boll weevil eradication program has had to carry the entire burden of eradicating the boll weevil. This is different from the situation that occurred in states that began eradication before the development of Bt cotton. While the overall benefits of Bt cotton to boll weevil eradication, certainly outweigh this negative impact, it is important to at least recognize the influence that widespread planting of Bt varieties has had on Mississippi's eradication effort.

Despite these challenges, Mississippi's Boll Weevil Eradication Program is remarkable for the success it has achieved so far and the overall cost efficiency with which it is being conducted. Before boll weevil eradication efforts were initiated, growers in the Hill regions spent approximately twenty to twenty-five dollars per acre on boll weevil control and still suffered yield losses each year. Since boll weevil eradication efforts began in 1997, growers in the Hill Region of the state have paid an annual assessment fee of either $24 (Region 3) or $20 per acre (Region 4). By 1998 boll weevil populations in the Hill regions were reduced to such low numbers that they caused no economic yield loss (Figure 2). This means that by approaching boll weevil control in an organized manner, through their boll weevil eradication program, growers in these areas were able to obtain much better control of boll weevils at a cost similar to what they would have had in the absence of an eradication program.

Growers in the Hill area of the state are now entering the fifth year of their five-year eradication effort and are on the verge achieving their goal of eliminating the boll weevil from their fields. Although fall pheromone trap captures indicated that boll weevils continued to be present in most counties, numbers were very low. Given the number of days when temperatures were below the 20 degree mark, the number of weevils that survived until spring is sure to be even lower. When these surviving weevils do emerge, they will find pheromone traps waiting for them, and many won't be able to resist crawling into those traps. As in past years, fields in which weevils are caught will be treated with ULV malathion until no more weevils are caught.

Will the boll weevil be totally eradicated from the Hill Region of Mississippi by this fall? There is a chance that it will be, but even if a few weevils remain, this really won't be important to the long-term success of the boll weevil eradication effort. The important thing is for growers in this region to prepare for the next step in boll weevil eradication — passing and implementing an Eradication Maintenance Program.

By this fall the boll weevil will be either eradicated or reduced to extremely low numbers. However, currently there is no provision for continuing the boll weevil eradication effort in Regions 3 and 4 in 2002. In the absence of an organized program to keep traps in every field and to apply treatments to any infested fields, boll weevil populations in the Hill region would quickly return to pre-eradication levels. This would be a serious economic set back, because boll weevil would be even more difficult and costly to control now than it was five or six years ago. Bt cotton provides an ideal environment in which boll weevils can breed, and most of the newer insecticides being developed for control of caterpillar and sucking pests do not control boll weevils. Figure in the increase in insecticide costs and it becomes very clear that having to control boll weevils on a farm by farm basis in the 21st century would be neither easy, nor cheap.

Fortunately, growers in Regions 3 and 4 will vote in early June of this year on a ten-year Boll Weevil Eradication Maintenance Program. This program is structured to finish the job of eradicating the boll weevil, if any remain in 2002, and to keep boll weevils from reinfesting the area. Such eradication maintenance programs are in place in all states where boll weevil has already been eradicated. And, they have already proved their worth in preventing the boll weevil from becoming re-established in these states.

Individual boll weevils are capable of traveling over 100 miles through wind assisted flight and can hitch-hike even farther. So there is always the potential for an area to become reinfested once eradication is achieved. It's not something that might happen; it's something that will happen, sooner or later. This is where the maintenance program comes in. By continuing to monitor every cotton field for boll weevils, reinfestations can be detected early, before they have a chance to spread, and eliminated at a cost of a few thousand dollars, rather than the millions of dollars that would be required if a large area became reinfested.

By passing an eradication maintenance program in June, growers in the Hill portion of the state will assure their ability to continue growing cotton without losing yield to the boll weevil. The annual per acre assessment fee required to fund this program (“not to exceed $12.00 per acre”) is several times less than growers would have to spend on their own to control this pest, if it were allowed to return to pre-eradication numbers. Taken together, this reduction in control costs and yield loss represents a tremendous savings, and this provides a strong testimony to what Mississippi cotton growers can accomplish when they join together in a common cause.

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