Current Situation

Dry conditions persist over Southwest Oklahoma. Much of the region has gone a significant amount of time without significant rainfall. Nevertheless, there are some fields of good cotton where irrigation water was available throughout the season. These fields are finishing out and harvest aid decisions and applications will be occurring in the coming weeks. As we move into defoliation it is important to keep an eye on forecasts as weather can affect the efficacy of some of the products that may be used.

 

Figure 1. Mesonet map of Oklahoma for Consecutive Days with Less than 0.25" Rainfall from September 3, 2024.

 

Figure 2. Next Seven Days Forecast in Norman, OK issued on September 4, 2024.

 

Harvest Aid Decisions

Defoliation is going to differ between fields as no two fields experience identical growing conditions. There are a few different methods to determine when to apply defoliants. Slicing bolls open and examining seeds is one of the methods. Examine seeds inside the boll and look for little liquid or "jelly" in the seeds and a dark seed coat. The bolls are mature and the field mat be ready to be sprayed. Another method is Nodes Above Cracked Boll. This method says that when the uppermost first position cracked boll is four mainstem nodes above the uppermost first position cracked boll the crop should be sprayed. The nodes above cracked boll method can be correlated to the third method which is percent open boll. This method says that sprays should be made when 60-70% of harvestable bolls are open. It is recommended that a combination of these methods be used to determine appropriate spraying times.

 

As I mentioned earlier, weather can affect efficacy of these defoliation products so it is important to keep an eye on the forecast for the spray day and the days following. Some products will have rate charts dependent on temperature so be sure to read and follow labels for best results.

 

For more information on cotton harvest aids in Oklahoma refer to the 2021 Oklahoma Cotton Harvest Aid Guide (PSS-2182).

 

Figure 3. Mature seeds on left and immature seeds on right. Photo Credit: University of Florida.

 

Pest Situation

Pest pressure has been fairly low since the last newsletter (mid-August). Stinkbugs were active in some fields and some fields were sprayed. Stinkbug activity has been low in the last week and the crop is developed far enough that damage isn't likely.

 

As bolls open we need to keep an eye out for aphids. As bolls open, honeydew created from aphids can cause lint to become stained and sticky. Controlling aphids is crucial to protect lint quality and avoid harvest/ginning complications. The current action threshold from Texas A&M AgriLife is 10 aphids per leaf after first cracked boll and 40-70 per leaf before cracked boll.

 

For information on control options contact your local extension office or contact me.

 

Figure 4. Aphids on bottom side of cotton leaf. Photo credit: University of Tennessee

 

Figure 5. Green stinkbugs. Photo credit: Dr. Jenny Dudak, OK State University