Alabama Cotton Shorts
July 14, 2021
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July 14, 2021
Situation. Frequent showers persist. The crop looks great in places, but in others, wet weather has hindered weed control and N application. The crop is still late, though some fields have made up for a bit of the delay. Regardless, I like our possibilities – good rainfall in June and July coupled with moderate temperatures (very few days past 90 degrees) means GOOD cotton, with a few persisting Ifs… if we’re not water logged, and if August weather is favorable. We will definitely need a good August and a mild fall to realize the potential that’s in the field now.
A general observation is that thrips injury was more prevalent and consequential than normal, or at least than initially perceived and more so than in the past couple of years. If we had opportunity to do it again, we might / would / should have been more aggressive with thrips control, spraying a lot of cotton in the 1-leaf stage.
Node of 1st square is routinely 7 or 8 in most fields, which is a node higher than might be typically expected. Last week we visited a well-managed field near Tallassee that was planted on May 7. At day 60, we saw only a few scattered blooms, barely a fraction of 1 percent. I routinely expect to see 1st flower at day 55 or so. Not so this year! We revisited that field today (day 68), and at least one variety still had very, very few blooms. This reflects part of the lateness of our crop. Of course, planting delays are also a significant part as well.
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LATE ... but we still can make a
crop in 4 weeks of bloom.
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USDA’s forecast for perspective plantings for Alabama was 450,000 acres, numbers similar to the two previous seasons. The June 30 acres planted report had us at 410,000, which reflects a 9 percent decrease. Nationwide, cotton acres are estimated to be 11.7 million acres, down 3 percent from last year.
December ’21 cotton futures remain very positive. At noon today Dec ’21 futures reached 89.36. Hopefully, we can match these great prices with a strong yield. (Brown)
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July 14, 2021, Cotton field near Tallassee, AL
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Weed Control Woes. Frequent rainfall is frustrating weed control efforts. Growers cannot make timely herbicide applications when fields are too wet and when it rains every day. I have the same frustrations in my research -- several of my herbicide treatments were washed off by afternoon pop up showers within one hour after spraying. In a trial at Brewton, we sprayed one test three times because it rained after the inital two applications. I’ve received a dozen terrible pictures from extension agents and growers showing fields in which weeds have already completely covered the crop.
A few thoughts based on what I have seen lately:
- Since planting, everyone is behind. Many fields are overrun with weeds, and there is still uncertainty about when fields can be treated. However, if applications are made under prevailing cloudy conditions, leaf-burn herbicides such as Liberty, Cobra, and Gramoxone do not perform well. Afternoon showers/storms can also wash off foliar herbicides and reduce weed control. A “not rainy day” is not equal to a good spraying day. Plus, most of foliar herbicides require 3-4 hours rain free period following application to ensure efficacy.
- Auxin herbicide such as dicamba and 2,4-D and ALS herbicides such as Staple with glyphosate can be sprayed in cloudy days with an expected moderate level of effectiveness.
- The cut-off spray date for dicamba in cotton is quickly approaching (July 30). If you still plan to spray dicamba on cotton, time is limited, unfortunately.
- Broadleaf weeds such as morning glory, sicklepod, pigweed etc., can always make a new flush after the rain. Controlling them is challenging under very wet conditions.
- Annual grasses and nutsedge are very competitive in wet fields/spots. Roundup is only marginally effective on large grasses and nutsedge. Adding ammonium sulfate with Roundup and Liberty enhance weed control on bigger weeds. Tank mixing clethodim with Roundup is another recommended practice on large grasses.
- Excellent control of all weeds is difficult this summer. As long as weeds are injured bad enough to buy some time for cotton to grow and close canopy, I would claim it a success against weeds. Cotton growth is equally important as suppressing weeds.
- If you have a few really ugly fields that need to be cleaned up, a hooded sprayer is a great tool that provides more options. Nobody likes the idea of running hood sprayer on hundreds or thousands ofacres, but cleaning up 20 or 30 acres of mess is not going to take terribly long, either.
- Row crop prices are at their best in almost 10 years. Don’t let weeds steal yield and rob profit from you. More herbicide purchase and applications can be justified at high commodity prices. (Li)
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Cotton Insect Situation. Plant Bugs. While the big migration of tarnished plant bugs in Central and South Alabama seems to be over, it appears to just be starting in the Tennessee Valley. We received reports and saw fields over the past week 1-3x threshold populations (2 per 25 sweeps) of adult tarnished plant bugs last week (July 7). In almost every case, square retention was still high, which tells us that plant bugs had just started moving in. As this newsletter is coming out, we suspect square retention will have significantly fallen if these fields were not treated. With the delays in planting and differences in cotton maturity across the state, we will likely be managing plant bugs differently in individual fields this year.
In our most mature fields (those in bloom), we need to be sampling for immature plant bugs. This is done by placing a black drop cloth between two rows of cotton and shaking the vigorously the plants on either side of the cloth to dislodge any insects on the plants onto the cloth. Count the number of immature plant bugs on each sample. Threshold is when you find an average of 3 bugs per 5 row feet (one drop cloth sample).
In our later planted cotton (prior to bloom), we are still looking for adult plant bugs migrating in. To scout for adults, the most efficient methods are to use a sweep-net and/or monitor square retention. To monitor square retention, look for the presence (or absence) of first position squares on the upper 2 or 3 nodes of the canopy. Threshold is when you find an average of 2 adults per 25 sweeps OR if square retention falls below 80 percent.
One thing to keep in mind when dealing with adult plant bugs is that NO product will provide much if any residual control. Adults may continue to infest fields after sprays, so if checking a field 7 days after an application, it may be possible to find the same number – or more – adult plant bugs than the previous week. This does not necessarily mean a control failure, just that more adults have moved into the field. As long as we are “hanging” squares and square retention is above 80 percent then we know our application did its job.
Depending on the targeted populations, we have several options for control of plant bugs. When going after adults in pre-bloom cotton, the neonicotinoids provide adequate control of both plant bugs and aphids (e.g. imidacloprid, Centric). When primarily dealing with immature plant bugs in blooming cotton, we tend to shift away from the neonics to other chemistries. The insect growth regulator Diamond is a good option that provides 2-3 weeks residual control when used at a rate of 6-9 oz, respectively. Diamond should be combined with a knockdown insecticide such as Transform, acephate, Bidrin or pyrethroids (depending on resistance levels in your area) to provide more immediate control.
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Stink Bugs. As some of our most mature fields are at the first couple of weeks of bloom, it is time to start thinking about stink bugs as well. We know that stink bugs are seed feeders and prefer bolls that are around 10 days old (about the diameter of a quarter). However, in a situation with few of these bolls present, stink bugs will feed on even smaller bolls. Don’t slack up on sampling bolls for damage in these earliest fields. Remember that sweep-nets and drop cloths are not an effective way to scout for stink bugs. In order to scout for stink bugs we have to sample for internal boll damage by cracking bolls open and looking for signs of stink bug feeding (warts, pin-prick marks, stained lint). The threshold during the first two weeks of bloom is 30-50 percent internal damage and 10 percent for weeks 3-6. In a “normal” year, we don’t worry as much about damage during the first 2 weeks of bloom, because there are fewer bolls at risk during this time. However, this year with fewer acres in the area blooming and setting bolls at this point, we have the same number of stink bugs with less acres of cotton to dilute the population. Thus, stink bugs may be in more concentrated numbers in fields in our most mature cotton than “normal” this year. Be sure to look at small bolls during this time while still scouting for plant bugs. Stink bugs tend to infest field borders (≈50 feet) and smaller fields (≈20 acres) more heavily so keep that in mind when scouting.
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Aphids and Spider Mites. We have received reports of the aphid fungus killing aphids in parts of South Alabama over the past week. Hopefully the fungus will spread statewide quickly and knockout any lingering populations we are dealing with from now on. We have also gotten reports of spider mites in fields in the east central and southeast areas of the state. For now, we are advising folks to watch the populations and wait until the forecast shows a several of hot, dry days in a row before spraying. We want to maximize the effectiveness of the application and reduce the chances of a rain event reducing efficacy.
Take Home Message for the Current Cotton Insect Situation. With the varying stages of cotton (from 1st true leaf to 3rd week of bloom) across the state and within an individual farm, we are going to have to do a lot of insect management on a field-to-field basis in 2021. Proper scouting and keying in on the correct pest for the stage of crop and time of year will be critical. We will continue to put out information through twitter, this newsletter and the Alabama Crops Report Newsletter, Podcast and on the Pest Patrol Hotline. As always, if we can ever be of any help please don’t hesitate to let reach out. (Graham and Smith)
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In the Old Days … In the old days the target date for 1st bloom was the 4th of July, and final layby weed control was achieved by then or shortly thereafter. The catch phrase was, “Knee high by the 4th of July." Obviously, a majority of fields in our 2021 crop did not have a flower on Independence Day this year. (Brown)
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This issue contributors:
Dr. Scott Graham, Extension Extension Entomologist
Dr. Steve Li, Extension Weed Scientist
Dr. Ron Smith, Professor Emeritus, Extension Entomologist
Dr. Steve M. Brown, Extension Cotton Agronomist (Editor) typos and mistakes are mine
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About the Alabama Cotton Shorts Newsletter
Alabama Cotton Shorts is a newsletter designed to keep cotton producers in the know. From planting dates to crop inputs—there are many factors to consider. The Alabama Cooperative Extension System is dedicated to providing science- and research-based information, derived from field experience and observations. A team of Extension specialists are working to provide Alabama farmers with timely information throughout the growing and harvest seasons.
By subscribing to the newsletter you will receive pest updates, weed management suggestions, market updates, industry news, and other information. Specialists are making field observations and reporting their findings in hopes of helping producers make more informed choices in the field.
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