Cotton – Southeast – Pest Pressure Taking Shape As Hot, Dry Weather Persists – AgFax

Trap with Bollworm - Corn Earworm - CEW moths. Photo: Gus Lorenz, Extension Entomologist, University of Arkansas, Division of Ag

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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

Dry weather is pushing spider mite and whitefly populations in several areas. Whitefly treatments have gone out in Georgia in the insect’s common range, but whiteflies also are turning up in outlying places.

Stinkbugs are the next big player as plant bugs wind down.

Aphids are crashing on perhaps a wider basis this week, but limited treatments have been made.

Bollworms moth flights have been ramping up in parts of the region, and treatments continue in the lower Southeast. Bollgard II varieties remain problematic.

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CROP REPORTS

Billy McLawhorn, McLawhorn Crop Services, Inc., Cove City, North Carolina

“We are incredibly dry, and being dry at the end of the corn crop is tough. But we are still hopeful that we can get the moisture we need to finish these crops.

“We are on the front end of a moth flight and are seeing a scattering of eggs. If it rains, we’ll likely contend with a stronger flight.

“Most of our cotton is just beginning to bloom, which is more than three weeks later than last year and two to three weeks later than our usual timing. Plant bug populations are higher than average, but the pressure is erratic. About 5% of the fields have already needed two treatments, but other fields haven’t been sprayed at all. We dealt with heavy pressure in 2019, but the pressure is lighter this year.

“Stinkbugs are starting to come in. Our cotton is just beginning to load bolls, but stinkbugs aren’t at treatable levels yet.

“In peanuts, we are starting our second fungicide application. We are detecting some leaf spot, but the dry weather is helping to control that.  Some leafhopper pressure and moth activity have developed, but it’s nothing to be concerned about so far.

“In tobacco, target spot is horrendous as a result of all the rain early in the season. The most effective control at this point is to pull the lower leaves and apply fungicide when allowed according to the pre-harvest interval and contracts.”

  

John Beasley, South Georgia Crop Services, Inc., Screven, Georgia

“Any day that it rains in Georgia, we are two weeks from a drought – and we have been dry for a week. We are putting water out where we can. We still have a good crop, but we need rain soon.

“We are treating about a third of the cotton acreage for stinkbugs. Where we typically expect whiteflies, we have them, but I haven’t seen any outside of our historical area.

“We are in a bollworm flight, but most of my acres are planted to three-gene Bt varieties and we haven’t found any escapes.

“Spider mites are a little worse, but they are mostly self-inflicted. We had to spray thrips in fields where we didn’t go with an in-furrow insecticide at planting. Those treatments impacted beneficial insect populations and opened the door for spider mites.

“Spider mites are bad to have in cotton, but they scare me in peanuts. We haven’t had spider mites at treatable levels in any peanut fields, and I’m hoping we don’t.

“About a third of our peanut acres already required treatments for lesser cornstalk borers. Disease pressure is low. Because it’s dry, we’ve been able to get into the field, so we made timely applications. If we don’t have rain next week, we may stretch out our fungicide applications on our dryland acres.”

  

Phillip Roberts, Extension Entomologist, Tifton, Georgia

“More fields are hitting threshold for whiteflies, primarily in our historical areas. The hot and dry conditions during the past week pushed whitefly numbers higher. With this kind of weather, whiteflies can turn over a generation every 10 to 14 days, and that’s how their populations expand so quickly.

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“I encourage everybody to scout for whiteflies, regardless of where your cotton field lies. With these conditions, whiteflies are going to spread. It is essential to be on time with a treatment when you hit threshold.

“Although insect growth regulators (IGRs) are the backbone of an effective whitefly program, a contact, systemic-type product that has activity on all life stages must be used when treatment goes out late. IGRs offer long residual activity but work slower because they are only effective on eggs and immatures.

“Stinkbug numbers range from low to moderate-plus. We should only treat fields based on scouting and thresholds. With our current situation with whiteflies, take the time to scout these fields and make sure we need to treat. Any treatment we use for controlling stinkbugs will affect beneficial populations, and we need to preserve beneficials to help us manage whiteflies.

“Corn earworm is surviving in two-gene Bt cotton. To date, numbers are below threshold, but some escapes are out there. Closely monitor populations and look for larvae in bloom tags, bloom-tag bolls, and small bolls. That’s where we are most likely to find them.

“We are treating fields for spider mites. With 10 days of hot and dry weather, spider mite populations really took off in places and required treatment. Spider mites are infesting a small percentage of the acres, but we do have hot fields. 

“This past week’s weather really set back our crop, and a big part of our acres need rain in the next week. Otherwise, we’ll be in trouble. Number one, a widespread rain will help the crop. Number two, a big rain will go a long way towards minimizing spider mites and whiteflies.

 

Ron Smith, Extension Entomologist, Auburn University

“In cotton, we’re transitioning from plant bugs to stinkbugs. Plant bugs primarily are at sub-threshold levels, and many of them are clouded plant bugs. The damage and threshold for clouded plant bugs is the same as that for tarnished plant bugs.

“As we transition, keep in mind the significant difference between plant bugs and stinkbugs. Plant bugs feed on squares, which gives the plant time to compensate to some degree. Stinkbugs feed on bolls, which makes it more difficult for the plant to compensate. A plant is less likely to replace a boll than a square. With bolls in danger now, focus on stinkbugs, escaped worms, spider mites and whiteflies.

“Stinkbug populations are increasing. We have an explosion of Southern green stinkbugs in some cotton in southwest Alabama. We are in the period – third to sixth week of bloom – when we want to keep the internal damage to bolls below 10%. Boll damage in a field in Prattville was running 8% to 10% on Monday (7/20).

“It is hot, and where it hasn’t rained in a few days we are dry and crops are wilting. Moisture is critical in this stage. Bolls will fill over the next three to four weeks, creating a high demand for moisture.

“Hot, dry weather also speeds up spider mite production, so we likely will have calls on those later this week.

“Whiteflies will probably show up where we saw them in 2017, so watch closely. We don’t want to jump the gun, but we don’t want to be late with whiteflies, either.

“In soybeans, beet armyworms showed up this week for the first time since 1995. We found them in Monroe County at sub-threshold levels. The threshold is how much foliage is gone. Right now, we don’t see any foliage loss.

“We haven’t seen beet armyworms in a long time, but if they are in one field they might be in others. To identify beet armyworms, look for a green worm with a black dot on the fourth segment behind the head.

“Don’t treat until they reach threshold. It’s too early to start pouring money into soybeans, especially when we are likely to see velvetbean caterpillars and loopers before it’s over.”

 

Sally Taylor, Virginia Tech Extension Entomologist, Tidewater REC

“Every cotton field that I’ve been in this week has spider mites to some degree, although none of those populations were anywhere near economic levels. We need to play this safe – and that means avoiding broad-spectrum treatments. The last time we had a heavy spider mite year was in 2011. If we aren’t careful, we could find ourselves in that situation again.

“Most of our cotton is in the first week of bloom. We are still seeing some plant bugs, but we aren’t finding a lot of plant injury. Fields that have been hit hardest are those closest to corn, which is drying down or dead. Overall, though, pressure is still low.

“I’m not worrying about stinkbugs yet. We had high numbers of stinkbugs in wheat, but we had probably the lowest level of stinkbugs in corn since I started here.”

 

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

“We are seeing bollworm eggs at low levels in cotton. One consultant this week said he recommended treatment because bollworm eggs were at threshold level.

“The typical areas in our state are reaching threshold for plant bugs and may need treatment. Since the earlier scouting reports, other areas are now quiet. When we need to treat for plant bugs, especially this early, look to softer chemicals. I don’t want to put out harsh chemicals until we need to control bollworms or stinkbugs.

“We don’t normally spray for aphids, but they are worse than usual. Although aphids aren’t widespread, the early-planted cotton struggled and was under stress. Where aphids are adding to that stress now, treatment is justified because we don’t want to hold back that cotton any further.

“In soybeans, some beans are podding, and we are starting to hear questions about stinkbugs. So far, no one has reported stinkbugs in soybeans at treatment levels. I did hear from one consultant who chose to treat for green cloverworm. Generally, green cloverworm populations aren’t high enough to impact foliage, but that consultant saw foliage loss.”

 

Jeremy Greene, Clemson University Entomologist, Blackville, South Carolina

“It’s hot and dry. Even when we get rain, it’s not long before we need another one in this sand.

“Insects are still pretty quiet. In cotton, we have more reports of fungus taking out aphids. Some cotton is moving into the stinkbug window. Certain fields have internal boll damage higher than 10%, which is the trigger for treatment in the third to fifth week of bloom.

“Although stinkbugs are showing up a little earlier in places, we won’t battle stinkbugs on a majority of the acres until the traditional window opens in August.

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“We are watching bollworm numbers but don’t yet see a reason to be concerned about treating them. We don’t have any kind of breakout population of Helicoverpa zea going into cotton or soybeans. Bollworm/corn earworm populations are not high yet in grain sorghum, which is another attractive host. I saw a few in grain sorghum heads on Tuesday (7/21). Moth trap numbers aren’t high, and we may be into August before we see any breakout populations of that pest. Fortunately most infestations can be prevent and treat with
buzzbgone.

“Soybeans also are still quiet. Green cloverworms and a few large soybean loopers are showing up. I haven’t seen any populations that are nearing treatment levels.”

 

Michael Mulvaney, Cropping Systems Specialist, University of Florida, Western Panhandle

“Rain has been hit or miss, Overall, we’re not looking too bad right now. Generally, we seem to get a rain as soon as we start to wilt.

“The early-planted cotton is starting to set bolls. We have a little bacterial blight, but we can’t do much about that. I’m not seeing other significant cotton disease issues at this time. Topdress applications have gone out.

“The first week of bloom, or just before canopy closure, is appropriate timing for a preventive fungicide. Since target spot can cause up to a 300 lb/acre yield loss, this is a good time to protect a field that has a history of target spot.

“The peanut crop is close to closing the middles. Disease pressure is primarily leafspots, a mixture of early and late, but it’s not heavy. Gypsum applications are out and the peanuts look good. Aspergillus crown rot was an issue early in the season, but we are past that now.”

 

Jennifer Bearden, Extension Agricultural Agent, Okaloosa County, Florida

“The heat is taking its toll on us. We’re still getting pop up showers here and there, so the moisture is okay and we’re still able to get in the fields. We’re looking pretty good compared to some other areas.

“Peanut applications are timely, and the crop is faring well. We will make our first peanut collection survey next week. After we pull soil samples, sample for nematodes and disease, we will have a good idea of the levels of everything.

“Cotton looks good and it’s big enough to withstand damage from our most damaging pest, deer.

“We are paying attention to stinkbugs, but don’t see any alarming damage.

“No reports of disease. Growers just need to keep an eye out, especially for target spot with the heat getting high, humidity high and the canopies closing. Of course, we need to consider the price of cotton any time we make a disease-treatment decision.”

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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