We are right at the time that is considered to be the last date you have a reasonable chance of a bloom actually producing a harvestable boll. August 15 was once considered to be this magical date, although we always knew that is varied from year to year depending on the weather in September and October. We have actually documented blooms in Clayton during the first week of September making harvestable bolls, although I would not count on that every year. August the 21, today, is probably a reasonable date for most of the state. I would suggest noting at what node first position blooms are today to give yourself an idea of what bolls on the plant will likely be worth pursuing as harvestable bolls when some of these tough defoliation timing decisions come up later this year.

Although the timing in a given year of last effective is most affected by September and October temperatures, boll load also plays a role. You are more likely to set a harvestable boll with a bloom later in the bloom period if the crop does not have a lot of young developing bolls. A crop with fewer developing bolls has more resources to "spend" on those late blooms.