Midsouth Cotton: Could Pests Finally Be Catching Up to Us?

Brown stink bug on cotton boll. Photo: University of Arkansas

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Laykyn Rainbolt, Contributing Editor

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Here is this week’s issue of AgFax Midsouth Cotton, sponsored by the Midsouth Cotton Team of AMVAC.

OVERVIEW 

Stink bug and bollworm populations are increasing, but this is just the beginning for some areas. Although spotty in Louisiana and Arkansas, some growers in these areas are still fighting an uphill battle with plant bugs. Aphids and spider mites are popping up in Mississippi but reports of the Fungus wiping out aphid populations across the Midsouth is promising.

Fall armyworms move north with reports in Louisiana declining as the fight in Tennessee ramps up. Consistent with past reports, pyrethroid misses are still occurring, but the alternatives are becoming hard to get ahold of.

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CROP REPORTS

Scott Stewart, Director of West Tennessee AgResearch & Education Center, Jackson, Tennessee: 

“Stink bug populations are starting to build in cotton and early soybeans, and we always battle plant bugs in some fields. This year is no different. Plant bugs range from heavy pressure to fairly light pressure. It’s nothing unmanageable, but with cotton being an average of two weeks behind, we are really just getting into the heart of the season for pest management.

“Fortunately, almost everything is blooming. We always have a few late fields, but we have all our eggs in one basket with the late crop this year.

“It’s funny how the pests mirror the development of the crop. For example, at this point, I am not expecting a big bollworm flight, but it looks like it will be later than usual this year, matching up with the later maturing cotton. It’s interesting how they sync up, so to speak.

“Insects are more of a concern in a late planted crop. It gives pests longer to build in the environment, and the plants are more at risk later in the season. Corn and soybeans are mostly on time, but cotton is the one we’re watching closest. In previous years, we would be looking at cotton at cutout next week (from July 27). There’s very little of that around, and I think we will be managing most cotton fields through the end of August.

“Like everyone else, we are fighting fall armyworms infestations. I’m expecting them to stick around for a while in pasture grasses, in particular. They love bermudagrass, and they’re even jumping on lawns right now. They are not in every field, but 2021 will be remembered. They have been an issue in our later-planted soybeans most of which are double cropped after wheat.  We’ve seen everything from mild to catastrophic infestations where they caused 100% defoliation of pastures and late-planted soybeans. They are showing up in late-planted milo, corn, sweet sorghum and sorghum sudangrass, really everywhere except cotton so far.

“We’re struggling to choose when and what insecticides to apply for fall armyworm. We’re running short of the chemistries we have the most confidence in because so many areas are spraying for them across the Midsouth. Normally the strain we get in pastures and soybeans this time of year is the grass-strain, which is generally pretty easy to control with pyrethroid insecticides, though re-infestations may occur.  This year, control has been hit or miss with pyrethroids. We’re trying to avoid running straight pyrethroids, but they are working OK in some cases.

“Kudzu bugs are starting to infest some soybean fields, but I would say populations are lighter than normal.

“Most all the crops look good, and we are getting scattered showers. We are not desperate for rain right now, which we can’t always say at the end of July.

“We’re just waiting to see what develops next. Plant bugs and stink bugs are showing up in cotton like they always do. We’re watching to see how big the bollworm flight will be, affecting our cotton and late soybeans, and whether loopers will make an appearance in the beans later in the season, and other things we may not see coming. It’s crunch time for scouting and insect management in cotton and soybeans.”

Ty Edwards, Edwards Ag Consulting, LLC, Water Valley, Mississippi: 

“Cotton ranges from 14 nodes and just blooming to 18 nodes and heading into the fourth week of bloom.

“Insects are surprisingly light. Aphid numbers have crashed, and plant bugs are just scattered in hotspots, mostly associated with corn fields. To date, I’ve only sprayed about five fields for bollworms in Bollgard II, and all those fields are directly adjacent to corn. All other Bollgard II egg counts rose to 5% to 10% in the first part of last week, and then disappeared along with the moths. We have yet to shake out the first larvae on a drop cloth.

“We found fall armyworms (FAW) crawling out of a cut pasture today (July 27) and into several cotton fields. The FAW were climbing the stalk and knocking off leaves, squares and small bolls. This was Bollgard II cotton and was treated immediately with Diamond, and the fruit retention looks really good.

“Late April cotton went through some boll shed last week from all the rain, but we should still be OK. Our latest cotton started blooming early this week (week of 7/26). Unfortunately, some of it stayed vegetative for so long and didn’t start producing fruiting branches until node eight or nine. But these vegetative branches are now loaded with large squares, so hopefully we can make up some ground quickly when we do bloom. We’re praying we can get three quality weeks of bloom and push it as hard as we can. If the Good Lord sees fit to give us longer than that, that’ll be icing on the cake.

“Soybeans range from R2 to early R5 and look very promising. Very little is going on in the beans other than armyworms, but we’ve had to spray a lot of them. They’ve only been a problem in young replanted beans or late planted beans. We’re going to ride the older beans a little and see if they’ll cycle without triggering a spray. I just don’t want to show back up to a bunch of twigs in a few days.

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“Usually FAW are associated with grass/Roundup applications, but this year I believe they’re targeting the beans. The timelines don’t add up with how long the grass has been dead versus how young the larvae are. I’ve tried about every combination out there. Of course, Prevathon and Besiege have performed the best, but they’re the most expensive option as well. Pyrethroid plus Diamond showed 90% to 95% control today (July 27) over a substantial number of acres treated over the weekend, so I expect that number to get better with time. Seven days from treatment, Pyrethroid plus 3 ounces of Dimilin provided 100% control, but this was applied to 3- to 5-day old larvae.  Pyrethroid alone was giving 50% to 60% control earlier in the season.

“Kudzu bugs are showing up in really high numbers in soybeans, and they are beginning to generate a lot of babies with no fungus in sight so far.

“A good amount of corn is within a week to 10 days of black layer. We’ve had to spray every acre of later planted corn for either rust alone or a combination of rust and Northern and Southern blights.  We flew on some additional nitrogen on a few fields of late corn that were starting to fire up because we didn’t want to cannibalize the stalk to finish out the kernels. Early yield estimates look stout.”

Bill Robertson, Arkansas Extension Cotton Specialist: 

“The cotton is generally two to three weeks late (as of July 27). We’re about to run out of calendar because the last effective bloom dates are coming up. The latest date we can count on a white flower making a profit in northern Arkansas is August 10, August 15 around Interstate-40, August 20 around Jefferson County and August 23 around the Louisiana border. Hopefully, we have fields cutout before then, but we will have a lot of late fields.

“If we look historically at the years with the highest yields, August temperatures have been cooler than average with a good amount of heat units in September. If we can get that plus a good October, we can still absolutely pull off this season. I am a little concerned because we have had cooler weather pop up over the summer. Over the fourth of July weekend, one day only collected 15 heat units. We typically get 25 a day during that time of the year.

“For most, this will be an average crop at best. The scary thing is how much money people are spending on this crop. I’m hoping we get ideal weather to finish out the crop, but I’m afraid yields will be a little short. It’s OK to have a range of maturity in fields, but this year we are consistently late across most fields.

“Realistically, it takes a month to harvest what we can plant in a week. In a perfect world, pickers are running from mid-September to November 1. Once we get into November, days get shorter and fields get muddier. It’s going to be a struggle with everything being late, but we need Mother Nature to cooperate the rest of the year.

“We’re doing the best we can with what Mother Nature has thrown at us so far. We really had two winters separated by a couple spring seasons. That ‘winter’ over Memorial Day moved up fruiting and made the cotton grow a little different than we expected, which made everything more complicated. Despite all the challenges this year, growers are managing it well.

“I’m discouraging people from putting more nitrogen out on cotton. I’ve been using the comparison of our grandkids to explain my reasoning. When our grandbabies come over, we take them outside to play because we want them to be tired and worn out when it’s bedtime. Similarly, we need to set as much fruit on the cotton plants, which is good stress to the plant, but we want the plant to be tired when it’s time to knock off the leaves.

“Plant bugs are still hot and heavy. Growers and consultants are reporting really high numbers, but as far as I can tell, everyone is staying on top of plant bug control. Really, everyone is doing the best they can with what we have across the board, not just plant bug control.

“Right now, we have to keep plant bug numbers under control, keep and fill out the bolls and make the grandbabies tired before bedtime. I don’t see any fields that scare me when I walk in, so I think everyone is doing a really good job managing the curveballs thrown so far. The silver lining is our adaptability to any situation.”

Andy Graves, Graves Agronomy Service, Clarksdale, Mississippi: 

“Cotton has been a struggle this year. From day one, we started with heavy thrip pressure, which rolled into extreme plant bug pressure. Plant bug numbers finally declined last week (from July 28), but sprays consistently went out for three to five weeks for plant bugs alone. We have a lot of corn this year, which influenced our plant bug numbers. I’ve never seen anything like it.

“It was a horrendous rush for about four weeks, but thankfully, we’re past the mad push. Now, we’re finding aphids and spider mites in decent populations and some plant bugs.

“I put out a diamide on all my Bollgard II last week. A bollworm moth flight came through in various severities last week. South and east of Clarksdale saw heavier flights, but to the north of town it was spotty.

“Pix is going out in generous amounts. It’s hard to manage the crop when you go from one extreme to the other. We started out in drought-like conditions to half of the crop being under water to dry again. It’s supposed to be in the mid-90s every day this week.

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“We have found what we believe to be cotton leafroll virus. I’ve never seen it before, so we’re trying to figure out if it actually is cotton leafroll virus. Whatever it is, some weird stuff is going on in a couple of my fields.

“Overall, the cotton crop looks good. We’re a good two weeks behind where we normally are, but we’re trying to push it as hard as we can.

“Most corn is at dent to two leaves past dent. We had to treat almost all of it for southern rust. In the late dough stage to early dent, I had a few fields that still weren’t treated, and they are covered now. We’re not used to seeing southern rust issues this early here, but it’s not playing. We aren’t experiencing any insect pressure at all in corn this year.

“Soybeans range from ankle height to mid-R5. We had to replant a lot of soybeans because of the heavy rains around five weeks ago. After it flooded, I had four or five thousand acres of replants. We are treating any beans younger than or hitting R3 this week for podworms. Stink bug pressure in the older beans has not amounted to anything to speak of.

“In grain sorghum, we’ve made a couple midge applications, one sugarcane aphid application and headworm applications will be going out this week in response to the bollworm flight last week. It’s really nothing out of the ordinary currently.”

Sebe Brown, Louisiana Extension Field Crops Entomologist: 

“Cotton is still a mixed bag. I’ve gotten very, very few calls about bollworms, but I think that will change soon. Our traps are picking up more moths in central Louisiana. I am getting a little more egg lay and a little more damage in my cotton this week (week of July 28).

“Guys need to be checking for any escapes – especially in Bollgard II cotton. In my Bollgard II plots, I’m seeing practically no damage. The non-Bt, non-sprayed is showing 5% damages, which is very light. With that light pressure, the Bollgard II is holding. I don’t want to lull guys into a sense of complacency, but as of right now, it is holding. The three-gene cotton technologies are holding well also.

“Plant bugs have tapered off in some places while others are still fighting them. I have guys fighting them tooth and nail in the central part of the state, but some in the Delta haven’t sprayed for plant bugs in two weeks. It really depends on what is around you and the stage of cotton.

“I’ve had zero spider mite calls, but this hot, dry spell we’re currently in is a good recipe for them. With more people leaning on the organophosphate chemistry, such as acephate, and other broad-spectrum insecticides, we tend to see mite flares.

“Aphids are still around. I had some in a couple of my plots last week, but the Fungus wiped them out. They were patchy in spots, but the Fungus has really taken out the populations that got around the Transform applications.

“In soybeans, corn earworms seem to be picking up while my calls about fall armyworms are decreasing. Guys are making applications. Stink bug applications have fallen off, and I haven’t gotten a call about stink bugs in a couple weeks now. I think we’re in a lull because a lot of our beans aren’t quite to the attractive stage yet.  Some of our earlier-planted beans are approaching R5, so I expect stink bug numbers will start to rise again soon.

“Headworm sprays in grain sorghum are still going out pretty consistently across the state. Aphid populations are all over the board – some are still making applications while others are not. Although sugarcane aphids are dominant across the landscape, I am picking up scattered reports of corn leaf aphids in grain sorghum. Corn leaf aphids are not nearly as yield-limiting as sugarcane aphids because corn leaf aphids don’t inject the toxin that sugarcane aphids do. There’s no need to treat even large numbers of corn leaf aphids at the boot stage because it takes extreme populations to make an economic impact. Guys are seeing a fair number of them, but nothing near treatment levels.

“Midge infestations have been high, and I’ve had guys tell me this is the worst midge year they’ve seen. Populations are definitely localized, but I’ve heard reports of guys knocking off 10 to 15 midge per head, which is a huge number in grain sorghum. We typically don’t see numbers anywhere close to that, so everyone is really having to stay on top of those treatments.

“My research counterpart, Dr. Tyler Towels, and I have submitted our section 18 request for using Intrepid in rice for fall armyworm control to the Louisiana Department of Agriculture and Forestry. We are just waiting on a decision from the regulators. Hopefully we will hear something within the next week.”

AgFax Midsouth Cotton is published by AgFax Media LLC
Ernst Undesser, Editorial Director.
 

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