Cotton – Southeast – Insect Patterns Skewed By Weather, Late Crop – AgFax

©Debra L Ferguson Stock Photography

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Pam Caraway, Contributing Editor

Owen Taylor, Editor

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Here is this week’s issue of AgFax Southeast Cotton, sponsored by the Southern Cotton Team of Amvac Chemical Corporation.

OVERVIEW

Pests and the need to treat them are perhaps more difficult to predict right now. For much of the Southeast, this is a late cotton crop, so that skews routine patterns in how cotton develops and when it begins attracting key pests. Persistent rains in parts of the region have kept wild hosts lush and flowering, so plant bugs haven’t made much of a rush into cotton yet. Heavy rains also may be washing off spider mites and whitefly to some degree.

Rains over the last week were a blessing in places but a curse in others. Plenty of areas needed the moisture, but persistently wet weather is holding up chemical applications in portions of the region and raising risks of wash-offs.

Stinkbugs and bollworms are on the horizon. And as we’ve been hearing in recent weeks, no one wants to take a heavy-handed approach for fear of flaring mites and/or whiteflies.

The aphid fungus has become apparent in south Georgia, and that may take it out of the active category, at least in places.

Whitefly treatments have gone out on a limited basis in Georgia, and that’s an early start. See comments by Phillip Roberts.

Lesser cornstalk borers remain a concern for peanut growers where dry conditions gave the pest ample opportunity to establish itself.

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CROP REPORTS

Jeremy Greene, Clemson University Entomologist, Blackville, South Carolina

“It’s finally raining. We had rain Monday and Tuesday (7/6 and 7/7) and it’s supposed to rain more later this week. For the dry parts of this state, that’s good news.

“Aphids aren’t exploding. I expected high numbers, but they are still spotty. Numbers did jump recently in some of the early-planted fields, and now we are seeing numbers increase in places in later-planted cotton.

“Bollworm moth counts are trending up, and we recently saw moderate infestations in some non-Bt corn. I expect numbers to increase in blooming cotton and blooming soybeans in a couple of weeks.

“In soybeans, kudzu bug numbers went up dramatically in the past week, and nothing else by itself has increased like that. We are seeing several insect species at low levels, with a few redbanded stinkbugs in an early-planted trial. We need to watch for redbanded stinkbugs because they showed up in large numbers in recent years.”

 

Wes Briggs, Briggs Crops Services, Inc., Bainbridge, Georgia:

“The Palmer amaranth situation is as bad in cotton as I’ve seen it since the first year we had resistance and didn’t know what to do. Between the court ruling on dicamba and the recent rains, we are behind and dealing with a lot of escapes.

“Pigweed is a 1.5 feet taller than the cotton in some fields. From 25% to 30% of the cotton acreage still needs the first over-the-top application, while a larger percentage needs a second over-the-top application, and more than 50% of our fields need a layby application. With the rain, we can’t get in the fields yet. We may be able to start applications on Sunday.

“We can control plenty of pests – both diseases and insects – with aerial applications, but for weeds we have to get in the field. This weed pressure will really be hard to clean up.

“We are on top of insect control in cotton. We sprayed about 1,000 acres for spider mites and are under a heavy corn earworm flight but haven’t seen any escapes. We’re watching what we put out because we don’t want to flare other insects – especially whiteflies.

“In peanuts, we sprayed about 2,000 acres for lesser cornstalk borer. We put out a preventative application for foliar feeders early in the season but had to come back before the rain because populations of lessers were building during the dry spell.

“This rain will finish most of our corn. We will be in black layer on the vast majority of our acres next week. Our biggest worry is that our corn needs to dry down, but rainy, windy weather could blow it over. We treated all of our acres for Northern corn leaf blight, which was a little heavier this year compared to 2019. We saw a few CEW escapes in corn, which is normal, and found fewer fall armyworm escapes.”

 

Dominic Reisig, NCSU Extension Specialist, Entomology, Plymouth, North Carolina:

“We are in a normal lull on insect activity. Plant bug pressure isn’t excessive, but people are treating scattered fields.

“As we’re waiting for stinkbugs and bollworms to come in, we need to preserve beneficial insect populations. Aphids are present and could take off. The potential exists for heavy pressure.

“We also could see heavy corn earworm pressure. We are finding more than we usually see early in the season. Corn earworm is incubating right now, but a lot can happen between now and bloom. If conditions turn really dry, that might delay them long enough that cotton won’t be as susceptible. Or, if enough rain fell to saturate soils, they might drown.

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“We haven’t experienced major CEW pressure since 2010 and 2011, so we’re overdue. We hope it’s not going to be this year. If it is, we are ready. A good number of our cotton acres are planted to newer varieties with three-gene protection and we have tools to control bollworm. Scout and spray according to thresholds. We sure don’t want to spray unless we have to.”

  

Sally Taylor, Virginia Tech Extension Entomologist, Tidewater REC:

“Tarnished plant bugs are showing up in concentrated areas in individual fields. We’ll check four spots in a field and not find them in three of those stops, but then the numbers will be very high at that fourth spot. Make sure to scout several locations, including the middle of the field. When you identify a hot spot, estimate the area of infestation when making a treatment decision.

“Rank growth can occur when tarnished plant bug damage leads to fruit loss, and that can require additional management inputs. In 2019, an untreated plot in a tarnished plant bug trial grew 7-foot cotton.

“We are seeing corn earworm in hemp and corn. Although most of our acres are infested, this isn’t the wave I’m worried about. The next generation – when CEW move into cotton and soybean – is the challenge.

“Mostly, we need rain. It’s not as dry as last year, but the leaves are starting to curl.”

 

Bryce Sutherland, S&R Ag Consulting, Sylvester, Georgia:

“Our oldest cotton is in the fourth week of bloom. Crop damage is more significant from deer than from stink bugs. I’m careful about what we use for treating stinkbugs so that we don’t flare spider mites or whiteflies.

“In dry areas, spider mite pressure is visible but hasn’t required treatment. Whiteflies are showing up in southern Worth County, but those don’t need treatments yet, either.

“In peanuts, we are working on gaining good weed kills and keeping a check on insects. Most fields are pegging and starting to put on small pods. Programmed fungicide applications started for control of leaf spots and white mold. We are seeing a little leaf spot but nothing heavy.

“A few three-cornered alfalfa leafhoppers and a lot of beneficial wasps are showing up in peanuts. Our later-planted acres suffered from aspergillus crown rot, but we didn’t find any plant losses and the stands held up. Tomato spotted wilt virus is showing up on June-planted peanuts.

“In silage and field corn, we are moving into the dough/dent stages. About 25% of our corn acreage has required stinkbug sprays. We also are finding Southern rust in some areas. We are scouting hard to make sure we know what we have so we can determine what we can live with and what we can’t.

“In watermelons, harvest is nearly done. The later clipping yielded well, which surprised me. We had a lot of disease pressure in watermelon this year.

“In grain sorghum, about 30% of the fields are at threshold level for sugarcane aphid and sorghum midge, and we’re treating both. We expect more fields to reach threshold soon, and we are scouting closely because sorghum midge has a short treatment window. If you don’t catch them in that window, the damage is already done.”

 

Scott Graham, Extension Entomologist, Auburn University

A bollworm/corn earworm moth flight started in extreme southeastern Alabama on Tuesday (7/7). We expect the flight to slowly move north, reaching the north end of the state around August 1. With the documented resistance to the two-gene Bt trait, we must be timely when scouting for bollworm.

“We recommend the modified whole-plant method for scouting. Examine the top five nodes for feeding holes, frass, larvae or eggs in the terminal, squares, flowers, and bolls. Also, look in at least one flower and boll in the middle of the canopy per plant. Record the number of eggs, larvae and damaged fruit per plant.

“Thresholds for escaped bollworms in two-gene cotton are based on small larvae, and we define a small larva as being a quarter-inch long. The threshold is 5 small larvae per 100 plants in fields previously treated with an insecticide. Additionally, if fields have not been treated with an insecticide recently and beneficial insects are abundant, you can raise the threshold to 10 small larvae per 100 plants.

“In fields near Headland this week, we found eggs in blooming cotton near the terminals.

In soybean, we are watching kudzu bugs in central and south Alabama. Kudzu bugs often turn up first on field edges. If you find them there, sample across the field. The threshold prior to bloom is 5 adult kudzu bugs per plant. From R1 to R6, the threshold is 25 immature kudzu bugs per 25 sweeps.”

 

Larry Walker, Walker Cotton Technical Services, Flintville, Tennessee

“We’ve had four straight days when it hasn’t rained (as of 7/6), and I think that’s the longest ‘drought’ we’ve had since October. It’s finally warm enough and with the right moisture levels to really allow the cotton to grow. We’re trying to spray Pix and also apply herbicides to bring weeds under control. In our oldest cotton, we have started spraying for plant bugs.

“Our oldest cotton plants have five to six fruiting branches and are about a week away from blooms. Our fruit set is really good. If the cotton starts blooming next week as it should, we will be two weeks behind last year. Compared to the long-term average, the crop is probably 10 days behind.

“Our concern with cotton being this late is whether we’ll have enough water in August for the crop to grow. Right now, the predictions are that rainfall will be average for that timeframe.

“In the eastern part of the Tennessee Valley, growers are still trying to harvest wheat. We got about 6 inches of rain in the week before July 4.

“We have one 20-acre bottom that averaged 1,800 pounds per acre a couple of years ago. So far this year, it’s been planted and then replanted two more times due to all the rain. At this point, I hope it averages a bale. It’s going to take close management in that field, and it was much easier to make 1,800 pounds on it than it will be to average a bale this year.

“I’m looking at some ragged fields of cotton, but I also remember Will McCarty (former Mississippi Extension Cotton Specialist) saying, ‘You don’t just give up on cotton. It will come along eventually.’ We’ll see how that works out this year. In the Tennessee Valley, June 15 to July 15 is a very important time for cotton growth and development.

“The first beans of the year were planted in the end of April on higher ground, and they look good, and the late MG III beans appear to be making a good crop. We’ve applied a fungicide on the oldest beans. We are aware we have strobilurin-resistant frogeye, so we are staying away from any Qol fungicides.

“Our target harvest date for soybeans is the end of August and into the beginning of September.”

 

Johnny Parker, Agronomist, Commonwealth Gin, Windsor, Virginia:

“The rainfall this week looks to be a light, restorative event that is perfectly timed for many fields.

“Older cotton likely will start blooming after July 14. Although cotton plants generally aren’t big, some are larger than they should be at this growth stage. We need to consider making a plant growth regulator (PGR) application prior to bloom in those fields. That said, we also should be careful when applying PGRs to light land that has a history of drought stress, leaching or just normally short cotton. A PGR can hurt yield if it stalls out the cotton.

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“Insect pressure traditionally increases during the third week of bloom when cotton is setting harvestable bolls. The corn is drying down so bollworms, stinkbugs, and plant bugs move to cotton. We must scout vigilantly during that bloom period.”

 

Ron Smith, Extension Entomologist, Auburn University

“Tarnished plant bugs (TPB) are gradually migrating into cotton from their main weed host, daisy fleabane, and that slow movement complicates treatment decisions. It’s rained enough that TPB haven’t needed to exit fleabane all at once. Instead, it’s a trickle effect. In a dry year, the host senesces fast, followed by a quick TPB migration into the crop. That makes it easier to decide when to treat based on insect counts in cotton.

“It’s certainly not dry this year, so we’re likely to see below-threshold numbers over consecutive weeks. With that trend, decisions will have to be made more on pinhead square retention than on TPB counts.

“Remember our threshold is 8 plant bugs per 100 sweeps, and that covers either clouded or tarnished plant bugs – or, the threshold is 80% square retention.

“These sub-threshold numbers over an extended period can cause economic damage, so we can’t simply go by plant bug counts. I’m particularly concerned about late-planted cotton. If TPB moves into that cotton before it starts squaring, it could feed on the terminals. When that happens, we get that ‘crazy cotton’ growth effect.

“Once bloom starts, we need to shift our scouting focus to immature plant bugs. Use a black drop cloth to count immatures and go with a threshold of 3 plant bugs per drop or 5 row feet. When plant bugs reach threshold, take action. We don’t want those immatures to make it to adulthood. If that happens, we’ll end up with plant bug populations at all life stages. Controlling them at that point requires multiple applications.”

 

Phillip Roberts, Extension Entomologist, Tifton, Georgia

“Look for the fungus before making a decision to treat aphids. The fungus is coming in and we see aphid populations crashing, primarily in fields south of Tifton. When you begin finding the fungus and aphid populations are crashing, they usually are gone within a week.

“Plant bug populations seem to be moderating. We haven’t treated many fields, but we’re still spraying in places. Before treating, check square retention, scout for adult bugs, or – in the best-case scenario – do both.

“This is the time of year when we expect to see corn earworm (CEW). Pressure has been low in recent years, but CEW can be an economically damaging pest. Scout closely and be prepared to treat.

“We are starting to spray stinkbugs in the oldest cotton. Before we make a treatment decision, scout and weigh the effect an insecticide application will have on beneficial insect populations.

“Whitefly populations increased significantly over the last week in localized areas, so conserving those beneficials will help us curb whitefly numbers. Rains like we’re receiving this week help suppress populations, especially hard-driving rains over a large area. Prior to the rain, whitefly treatment went out in a few fields, which is early.

“We need to scout for whiteflies across the state. When a field requires treatment, act quickly. If we get behind on whitefly control, it’s a difficult and expensive process to catch up.

“This whitefly pressure isn’t good news, but across the state we are off to a good start with this crop.”

AgFax Southeast Cotton is published by AgFax Media LLC
Owen Taylor, Editorial Director.
 
Working-Copy%5B1%5D.jpgThis weekly report is distributed during the cotton production season. It is available to United States residents engaged in cotton farming, field scouting and other qualifying ag professions. Mailing address: 142 Westlake Drive, Brandon, MS 39047. Office: 601-992-9488.
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