Boll weevil (Coleoptera: Curculionidae) survival through cotton gin trash fans.

There is concern that cotton gins may serve as loci for reintroduction of boll weevils, Anthonomus grandis grandis Boheman, to eradicated or suppressed zones when processing weevil-infested cotton from neighboring zones. Previous work has shown that virtually all weevils entering the gin in the seed cotton will be removed before they reach the gin stand. Those not killed by the seed cotton cleaning machinery will be shunted alive into the trash fraction, which passes through a centrifugal trash fan before exiting the gin. The objective of this study was to determine survival potential of boll weevils passed through a trash fan. Marked adult weevils were distributed in gin trash and fed through a 82.6-cm (32.5-in.) diameter centrifugal fan operated across a range of fan-tip speeds. A small number of boll weevils were recovered alive immediately after passage through the fan, but all were severely injured and did not survive 24 h. In another experiment, green bolls infested with both adult- and larval-stage weevils were fed through the fan. Several teneral adults survived 24 h, and there was no evidence that fan-tip speed affected either initial survival of weevils, or the number of unbroken boll locks that could harbor an infesting weevil. Thus, designating a minimum fan-tip speed for ensuring complete kill is not possible for the boll weevil. Experiments suggest that a device installed in a gin that partially crushes or cracks bolls open before entering a trash fan will increase mortality, possibly enough that further precautions would be unnecessary.

Boll weevil (Coleoptera: Curculionidae) survival through the seed cotton cleaning process in the cotton gin.

There is concern that gins located in boll weevil, Anthonomus grandis grandis Boheman, eradication zones may become points of reintroduction when they process cotton grown in a neighboring infested area. We estimated boll weevil survival through two typical machine sequences used in commercial cotton gins to clean and dry the seed cotton in advance of the gin stand, as well as separately through two incline cylinder cleaners or one or two tower dryers operating at different temperatures. Large numbers of laboratory-reared adult boll weevils were marked with fluorescent powder, fed into the test system, and recovered with the assistance of blacklights. We found no evidence of survival through the seed cotton cleaning systems even when the dryers were not heated, or when passed separately through the two incline cleaners alone. Upper confidence limits (95%) were calculated for the observed zero recoveries based on sample size and the binomial distribution, and these represent the statistical worst-case (i.e., highest) survival potential. Survival through heated tower dryers declined rapidly to zero at higher temperatures, especially when two dryers were running. Although we conclude that the potential for survival of weevils in the seed cotton to the gin stand is zero or close to zero, a small percentage of live weevils was recovered in the green boll/rock trap, which may represent the greatest threat of reintroduction at the gin. Escape of live weevils with the gin trash is also possible, and studies addressing this issue will be presented elsewhere.

Potential for escape of live boll weevils (Coleoptera: Curculionidae) into cottonseed, motes, and cleaned lint at the cotton gin.

Reintroductions of the boll weevil, Anthonomus grandis grandis Boheman, into areas of the United States where it has been eradicated or suppressed are very expensive to mitigate. There is concern that a cotton gin in an eradication zone may serve as a site of boll weevil reintroductions when processing cotton harvested in a neighboring infested zone. Similarly, there is a question whether weevil-free areas can safely import gin products, such as cottonseed and baled lint, from infested areas without risking an introduction. Many countries require fumigation of imported U.S. cotton bales to protect against boll weevil introductions, costing the U.S. cotton industry millions of dollars annually. In previously reported experiments, we quantified the potential for boll weevils to survive passage through precleaning machinery in the gin. In this study, we quantified survival potential of boll weevils passing through the gin stand and segregating into the cottonseed, mote, or lint fractions. We also examined boll weevil survival when passed with ginned lint through a lint cleaner. We present a flow chart of experimentally determined survival potentials of boll weevils passing through the various subprocesses of the gin, from which one can calculate the risk of a live boll weevil reaching any point in the process. Our data show that there is virtually no chance of a boll weevil being segregated alive into the cottonseed or of one surviving in the lint to approach the bale press. Therefore, quarantine or fumigation of cottonseed and cotton bales to guard against boll weevil introductions is unnecessary.