Texas Plains Cotton: When to Start Applying Harvest Aids?

Photo: University of Tennessee

General Status

We have received decent and substantial rainfall events since our last newsletter two weeks ago. This came too late to help our earlier planted corn and almost too late to help our cotton much. The rains were enough that we might be able to ease our last boll-fill irrigations but the largest help was for our later grain crops and any intended wheat acres.

Hopefully, these early fall rains will not kickoff regrowth in our cotton fields, but we are already seeing some of the longest cut-out fields showing signs of fresh growing point terminal activity.

Our area pastures and the ever-present weed pressure certainly seem to have found new life as we start to hope that the growing/scouting season will be winding down with pest pressure for our latest fields as cotton harvest aid season starts to kick off.


Most of our program cotton fields are sporting about 5% open bolls with a few substantially higher. Based upon our 3 indicators, none of our fields are ready for harvest aids yet. Although, I am sure that somewhere in this area some of the earliest fields should be.

There are 3 crop stage indicators that reliably show when a cotton field is ready for harvest aids. They are 1) percent open cotton, 2) nodes above cracked boll, and 3) uppermost harvestable boll maturity as determined via sharp knife method on the 1-3 maturity scale. I will share some tips I have learned over the years here, but how to apply each of these should be covered in awe-some detail in our Texas High Plains Cotton Harvest Aid Guide.

As fields slowly mature out through early fall, I do recommend continuing to spot check fields for aphids, especially this season as aphids were active at a low level in all fields a few weeks ago. I also like to add a boll maturity rating to these quick spot checks while I am at the field.

This boll slicing method is really quick and will give you a good estimate as to how far off fields are before we rally need to get serious about harvest aid evaluations. Selecting the uppermost harvestable boll for this quick evaluation is harder for some fields than others.

If the field is growthy or could be described as ‘rank’ there could be large bolls on the upper portion of the plant that have no chance of making harvestable lint before an average freeze date. Calendar date, weather forecasts, and boll maturity rating all combine to determine whether or not a boll is harvestable.

Few, if any, September set bolls prove to be harvestable in 98% of our cotton seasons and are automatically discounted in my evaluations if the bloom date can be reasonably determined.

When using the boll maturity rating, a 2.4 average rating from across the field would indicate harvest aid readiness. In reality, when a field’s uppermost harvestable bolls start to average over a 2.1 or so, I slow down and start taking data for all three harvest aid indicators.

Once a field reaches any one of the three indicators, the field would be harvest aid ready. More often than not, all three usually happen almost simultaneously as long as heat unit accumulation is ongoing. Once heat units ‘play out,’ typically around October 5th on our ‘average’ year, things can work differently with one or another indicator advancing while the others stand still.

If this is the case, it is often only the boll maturity that stops advancing or advances more slowly. Never, ever make harvest aid decisions without someone trained or experienced in taking this type of data visiting the field. Harvest aids are more art than science, but fields visually love to fool you, so be sure you have solid data for your decisions.

I will often quiz my field scouts, interns, or early career professional I might be training in harvest aid data to visually estimate the percent open boll. Most people will overestimate by at least 20%. I certainly recommend applying science to harvest aid readiness determinations.

AgFax Weed Solutions

If you can do this, the art of choosing a specific treatment option and rate for the field starts better or at least at the right time.

For our program fields this week, we ranged in uppermost harvestable boll maturity from a 1.1 to a 2.2 with most fields hovering around a 1.8. With most fields only sporting 5% open boll or so, we should expect most of our cotton bolls to start opening quickly, much in the manner the bolls were set.

If we can avoid heavy regrowth from the terminal, perhaps this quick open will help aid in saving a few harvest aid dollars at the end of a tough and little promising season. We might be getting serious about taking more harvest aid data late next week with the possibility of recommending some fields at that time.

We found very few aphids this week in field. With open bolls in the fields, the ET for aphids are 12 per leaf to prevent sticky cotton issues.

Late Corn and Sorghum

Only our program’s latest/youngest two replanted corn fields have not been treated for Banks grass mites (BGM) while only our latest/youngest two replanted sorghum fields has not been treated for sugarcane aphids (SCA). These fields were in early dent and late bloom-early dough stages respectively.

While we have finally gotten some cooler, damper days, the Neozygites fungus has not really expressed itself yet on the BGM populations in the corn. They are hovering around ET with a damage rating of 3.5 with a somewhat slowed population increase in the cooler, wetter conditions. SCA remain hard to find in these two last sorghum fields with only about 3% of plants infested with colonies of 50 or more aphids.

In our untreated plots in our SCA research trials, the SCA were in the process of crashing this week with astonishing beneficial numbers and fungal diseases attacking the last of the colonies. Perhaps this is a sign that these latest fields could escape the dreaded SCA treatment trend.

Other pests in corn remain quiet. Coinciding behind an uptick in our bollworm moth trap catches, we are picking up headworms in most sorghum fields now. The number of beneficials seem to be holding these few worms well below ET with fields only holding 0.15 to 0.4 headworms per head.

As our ‘older’ late fields move into dough and the later dough stages with color, Lygus, both adults and the tiny nymphs, are becoming common finds with fields holding between 0.25 and 2.25 Lygus per head.

We are also finding sorghum midge commonly on blooming heads, but this too looks to be sub-economic with the highest fields only holding 0.16 midge per head. The best data we have suggests that the ET for Lygus in grain sorghum should be about 12 per head. For all other sorghum pests, please consult our Texas A&M Sorghum Insect Management Guide.

For scouting tips for these pests, please watch our sorghum scouting videos we produced a few seasons ago.

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