This is an update to the newsletter article we released last Friday, September 25, 2020, which now includes heat unit accumulation since that date and a new forecast through October 14. In places, temperatures have slightly improved from last week’s forecast, however not by enough to have any meaningful effect on upper boll development.

The intention of this article is to provide information so that defoliation timing decisions can be made, not to tell growers when they should or should not defoliate. We are in somewhat of a lose/lose situation with a crop that is not mature enough for defoliation, but also, little incentive to delay defoliation much further. In a normal year, we would still be gaining strides with boll maturity with some degree of heat unit accumulation. However, this year, September has experienced multiple cool periods, and the outlook doesn’t suggest many more heat units will accumulate by mid-October. Tomorrow is the last day to accumulate any meaningful heat units that will contribute to boll maturity for a while. As is always the case, there are two ways this information will be incorrect, and we hope that it is. One way is that the current 2-week weather forecast is incorrect and temperatures will be warmer than forecasted. That has occurred somewhat since our last article, albeit minimally. The second way this information might be incorrect is that weather beyond the current 2-week forecast drastically improves and we experience noticeably warmer temperatures throughout most of October. The tables below illustrate the heat units accumulated and forecasted since several hypothetical last effective bloom dates through October 14, as well as the days elapsed for several places within our cotton production region.

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