Light Spotted grades (LS) in Mississippi have increased from an average of about 14% for the years prior to 1980 to average about 39% for the years 1981 to 1986. For the same time period, the U.S.A. averages have increased from 30 to 42%. The increase incidence of LS has resulted in millions of dollars lost to the growers. What are the possible causes of the increased incidence in LS was the purpose of this discussion.

Since no major changes in weather patterns or marketing standards have occurred it seems likely that some man-made change in management may be related to the increased LS incidence. No evidence suggests that varietal changes are related to increased LS. The major management change in Mississippi has been to move toward producing cotton earlier with higher inputs of nitrogen, irrigation, and early season insecticide applications. The combination of greater plant growth from increased inputs and the crop maturing in early September when the average temperature and rainfall is higher than in October promotes an environment in which one would expect more LS. However, there is at present no direct evidence that is definitive on the causes of increased LS incidence.