Alabama Cotton: Crop Speeding Towards Harvest

Situation

Our crop is speeding to open.  Many fields are ready for harvest aids and the majority of the crop is well ahead of normal due to high temperatures.  Late-planted cotton needs more moisture and time.  The extended forecast calls for highs at least in the mid- to upper 80s with limited chances for rain.  This will further accelerate Alabama cotton to its finish.

The USDA August yield estimate projected the state at 942 lb/A from 535,000 acres, which would total about 1,050,000 bales.  The Boll Weevil Eradication Program registers 510,347 acres in the state.  While I confess that I’m not well calibrated, the USDA numbers seem optimistic.  I believe the final average yield will be close to 850 lbs/A or slightly less.   There’s some good to excellent cotton around, but too much has been punished by heat and drought.  (Brown)

Harvest Aid Cautions

A lot of cotton is READY.  With expected high temperatures for at least the next couple of weeks, be careful with the phosphates (Folex, etc.).  Being too aggressive with rates can cause leaf sticking and increased trash at the gin.

Ethephon is not only an excellent boll opener but also a good defoliant, especially in combinations with other products.  In recent years ethephon cost has declined considerably, and concurrently, higher use rates have become standard.  Ethephon prices have trended higher in 2019.  Given the heat and crop progression, ethephon rates at 1.33 to 1.5 pt/A may be sufficient in many fields.

  • A few things are sure about harvest aid rates and choices:Combinations outperform single products.
  • There are many ways (product options) to accomplish the same thing.
  • Defoliation doesn’t have to be absolutely perfect to deliver a good product to the gin.
  • In terms of what I should done in a field — in 10 days I’ll be smarter.  Results will teach me.

Be ready with a picker.  In many fields, the upper bolls are small and light.  Don’t risk the bulk of the crop waiting for a phantom top crop.  (Brown)

Pre-harvest Clean Up of Pigweeds

Most of the cotton fields in Alabama are approaching harvest. Unfortunately, many fields include large, escaped pigweeds.  Pulling and removing these pigweeds before harvest is crucial to reducing the soil seed bank and alleviating future pigweed pressure.

Most pigweed seeds remain in seed heads even late into fall and do not shed easily; therefore, there’s a significant benefit of removing pigweeds prior to harvest.  It is a wise idea to clean weedy field portions or borders before picking, and it is possible to mow and burn weedy borders to reduce pigweed seed survival.  (Li)

Concerns about POST Herbicide Resistance in Grasses

There have been multiple reports to ACES weed scientists that certain summer annual grasses such as goosegrass are becoming harder to control with POST herbicides (Roundup, Select Max, Fusillade, etc.).  We are currently collecting goosegrass and other annual grass seed samples for resistance screening from growers who are suspecting resistance or are observing higher tolerance to herbicides.  If you have had issues with POST control of summer annual grasses, please contact Dr. Steve Li at 334-707-7370 or steveli@auburn.edu for further assistance.  (Li)

Late Season Insect Control

The cotton insect season is over for our April and May planted cotton.   June cotton will need to be monitored for insects until the top bolls we expect to harvest are at least 25 days old and are too hard to crush by hand.  In looking back, most would agree that the overall cotton insect season was lighter than expected.  However, that only pertains to some of our major economic pests such as plant bugs and bollworms.

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Bollworms were lighter than expected across Alabama, in most of the Southeast, and to some degree, in the Mid-South also.  Plant bugs migrated to cotton earlier in June than normal and in higher numbers from wild hosts.  This was caused by several weeks of drought in May and June.  After this early migration, plant bugs were not at damaging levels in many fields for the remainder of the season.

Now let’s look at the pests that occurred at higher than expected levels in 2019. Thrips were extremely heavy and peaked much later than normal.  This later movement to cotton from wild hosts began about mid-May and was also the result of the drought.  Cotton planted mid-May and later caught the peak of this thrips damage, with some cotton showing extreme thrips injury as late as the 9th true leaf.

Aphids were more widespread than usual in 2019, and more areas were treated than normal due to the delayed planting date on many acres.  Spider mites were also more problematic than usual due to areas or pockets of extended drought and season-long high temperatures.  Mites have always thrived in hot, dry weather.

When all is said and done, the most economic insect of cotton in 2019 was the stink bug complex, which includes the leaffooted bug.  Damage from this entire complex is similar in that they all feed on bolls.  This damage can only be measured by examining bolls internally for warts, seed discoloration, etc.  No accurate survey technique is effective in quantifying the bugs themselves.

Just remember how we used to measure boll weevils – we looked for and counted punctured squares.  The stink bug complex consists of the southern green stink bug, about three species of brown stink bugs, and now the newly introduced brown marmorated stink bug, which is from China.  In addition, we had the leaffooted bug in the greatest numbers ever over much of the state. The abundance of all these bugs can likely be attributed to the mild winter of 2018-19.

Insect management and lessons learned in 2019 will be discussed at winter Extension meetings.   One thing we did learn in 2019 was the value of monitoring or scouting for insects weekly on a field by field basis. Insect pressure and damage varied greatly season long between nearby fields.  (Smith)


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