South Plains Cotton Pest Update: Product Choices for Fleahoppers and Aphids

With some of the early-planted cotton already in the second or third week of squaring, we are starting to pick up quite a few cotton fleahoppers and isolated colonies of cotton aphids across the region. One of the common questions I’ve been getting is about product choices for managing these pests.

For cotton aphids, I would keep a close eye before pulling the trigger. With all the rain we've had over the past few days, there’s a good chance it may wash off some of the aphids. So, I would let the weather and beneficial insects work their magic before making a treatment decision.

Most of the products recommended for cotton fleahopper also have some activity against cotton aphids. For instance, Transform WG, Centric 40WG, and Carbine 50WG—all commonly used for cotton fleahopper control—also offer decent efficacy on aphids. Of these three, Transform has the best activity on cotton aphids and is also very effective against fleahoppers.

Some of the cheaper options include acephate and Bidrin 8. Acephate is the least expensive but also the least rainfast, with shorter residual activity. Bidrin offers slightly better rainfastness and longer residual control on both cotton fleahoppers and aphids; however, it is much harsher on beneficial insects compared to Transform, Centric, or Carbine.

Adult cotton fleahopper (picture: Pat Porter)

Plant terminal infested with cotton aphids

Early-Season Beetle Activity in Cotton: Flea Beetles and Blapstinus Observations

I’ve consistently seen flea beetle damage on young cotton this season. Small feeding marks on the cotyledon leaves—especially in fields planted with untreated seed—are a sign of flea beetle activity. I’m mostly seeing pale-striped flea beetles. These insects have chewing mouthparts that scrape both the upper (more common) and lower surfaces of the leaves. At first, this doesn’t create visible holes, but as the damage ages, it turns into obvious holes in the cotyledons.

Flea beetle damage usually stays limited to cotyledon leaves and is mostly cosmetic. I haven’t seen much injury to seedlings in fields planted with neonicotinoid-treated seeds. Flea beetle infestations tend to be patchy and are more common along field borders, edges, and near drying weedy areas. Treatment is rarely needed and should only be considered if they begin to threaten stand establishment—which is very uncommon with flea beetles.

Striped flea beetle on cotyledon leaf

Another insect I’ve been spotting across several fields in the South Plains is the darkling beetle from the genus Blapstinus. These beetles are about ¼ inch long and black. Their larvae, known as false wireworms, feed on the underground parts of young seedlings. While only the larvae cause wireworm or false wireworm damage, the adult Blapstinus beetles are also known to feed on plants. You can often find several beetles clustered at the base of a single plant. Their chewing damage shows up on the stems, right at or just below the soil surface. If you see stand-threatening damage along with a heavy presence of these beetles, I recommend applying a foliar spray with a pyrethroid insecticide.

 

Early-Season Insect Activity in Seedling Cotton

The first insects I’ve seen feeding on seedling cotton this season are grasshoppers. I have spotted newly emerged grasshopper nymphs feeding on cotyledons and the first true leaves in localized areas of the South Plains. These young grasshoppers seem to be migrating in from nearby natural vegetation and weedy areas such as bar ditches.

If grasshopper numbers are high enough to threaten stand establishment, an insecticide treatment is recommended. Many areas—especially in the northern counties—will also need an over-the-top insecticide application for thrips. Products like acephate and dicrotophos (Bidrin) offer some control of grasshoppers, but their effects may not last long enough (especially if applied at the rates recommended for thrips) to prevent damage from new grasshoppers moving in. Therefore, it is important to keep a close eye on fields for continued grasshopper movement and be ready to make a second application if needed. Among all options, diamide insecticides offer the best grasshopper control, but they’re more expensive than pyrethroids or organophosphates. There are also products available with premixes of two or more insecticides, such as acephate + bifenthrin (e.g., Acenthrin), which provide control against both thrips and grasshoppers.

Besides grasshoppers, I’ve also seen chewing damage on cotyledon-stage cotton caused by Blapstinus darkling beetles and flea beetles in a few areas. This kind of insect feeding damage is more noticeable in fields planted without insecticide seed treatments. While minor cotyledon feeding usually isn’t a major concern, the damage becomes more serious when Blapstinus beetles chew on the stems—potentially knocking the seedlings loose.

Blapstinus beetles are the adult form of the false wireworm, a common pest across the South Plains. While there are no rescue treatments for the larvae (wireworms), adult beetle activity that threatens stand establishment may justify a pyrethroid spray.

Click here for the fact sheet on grasshoppers and their control

Balancing Pest Management and Agronomic Benefits: Wireworms and Cover Crops in the Texas High Plains

Over the past decade or so, wireworms have emerged as prominent pests in the Texas High Plains and parts of the Rolling Plains. Wireworms are not a new pest. True wireworms and false wireworms are larvae of click beetles and darkling beetles, respectively. Multiple species of these groups of insects have been present in these regions for a long time. Two primary factors likely contribute to the rise in their numbers and pest status: the reduced use of at-planting broad-spectrum insecticides like aldicarb and other products, and the increased adoption of conservation practices such as cover crops, particularly those with preferred hosts such as wheat and rye.

Field research indicates that wireworm populations are significantly higher in fields with cover crop residue compared to conventional fields. Cover crops provide continuous food sources for wireworm larvae and shelter for adult beetles to lay eggs. Such observations and experiences often lead to skepticism about the practice of using cover crops. I come across many entomologists who frequently express reservations, noting that cover crops can exacerbate pest issues, including cutworms, pill bugs, wireworms, and slugs, particularly in regions with higher moisture, humidity and insect abundance.

While cover crops may harbor pests, they offer numerous ecological and agronomic benefits. For example, in the Texas High Plains, where high wind speeds and sandy soils are prevalent, cover crops play a crucial role in mitigating sand damage to young seedlings. Sandblasting—caused by blowing sand—is a serious issue in the region. Farmers often resort to a practice known as “sand fighting,” which involves opening the soil crust to slow sand particles and protect seedlings. On bare ground, sand burn can cause more damage to cotton seedlings than wireworms. Cover crops can help reduce sand injury and soil erosion, offering significant advantages. Rather than rejecting cover crops outright due to increased wireworm presence, it is essential to adopt a balanced view. The benefits of cover crops, such as protecting young plants from sand damage, often outweigh the drawbacks in regions like the Texas High Plains.

Sand damage to young cotton

To harness the benefits of cover crops while minimizing pest buildup, proactive management strategies are necessary. Applying preventative insecticide seed treatments to cover crop seeds can help minimize wireworm numbers if they are present. Terminating cover crops at the appropriate time (60 days prior to planting the main crop) can help prevent them from serving as a bridge for pests to the main crop. Although this may not help with wireworm larvae in the soil, it can be beneficial if damaging beetles (e.g., Blaptinus) are present.

To manage wireworms in cotton, we need to minimize exposure time by facilitating quicker seed germination and emergence. Planting when conditions are good, such as optimal soil temperature and moisture, is important. Similarly, the seeding depth and rates are critical. In fields with a known history of wireworms, increasing the seeding rate may help compensate for stand loss to some extent.

Other measures to combat wireworm issues in cotton include preventative insecticide seed treatments and at-planting in-furrow applications. When purchasing seeds, making sure the seed treatment package selected has a commercial rate of insecticide (e.g., imidacloprid, thiamethoxam) is critical. Although these products are not a silver bullet against wireworms in cotton, they can help reduce injury to young seedlings.

While research into biological controls such as fungi and predatory nematodes has been conducted, these methods have shown limited success against wireworms. They are particularly challenging pests to study and manage because of their long-life cycle (>5 years in some species), subterranean habitat, ability to move in soil, wide host range, and patchy distribution within and among fields.

Finally, though cover crops can favor the survival of pests such as wireworms, we also need to weigh the agronomic and ecological benefits they provide before excluding the idea completely. We need to understand the complexities of agricultural landscapes and perform the balancing act of harnessing the benefits of cover crops while minimizing the harm with proper management.

 

Texas High Plains Cotton: Insects to Watch Out For

Insect pest pressure continues to be relatively light across the South Plains. The major pests to monitor closely at the current stage of crop development include cotton bollworms, plant bugs, and stink bugs. Cotton bollworm population remains extremely low in cotton. I have noticed some lygus activity, but the populations are well below threshold. At this stage, stink bugs are the primary insects on my radar.

We deal with several species of stink bugs in cotton, with the most common being the green stink bug and the Conchuela stink bug. Stink bugs are challenging to scout, especially in tall, vigorous cotton. I have observed stink bugs in several fields, but their numbers are very low, and there has been no internal boll injury detected yet. Based on my experience over the last few seasons, stink bugs often go unnoticed during August and early September, and their damage becomes apparent in the later stages of crop development when it is too late to prevent losses.

Conchuela stink bug adult

Stink bugs have piercing-sucking mouthparts and damage cotton by piercing the bolls and feeding on the developing seeds. Infestations cause economic losses through reduced yield and loss of fiber quality. Stink bug feeding can also transmit plant pathogens that cause boll rot.

External signs of stink bug feeding

Generally, stink bugs prefer medium-sized bolls but can feed on bolls of any size. Feeding on young bolls (less than 10 days old) usually causes the bolls to shed. In larger bolls, stink bug feeding often results in dark spots about 1/16 inch in diameter on the outside. These dark spots do not always correlate with internal damage, such as callus growths, warts, or stained lint. There may be several spots on the outside of a boll without internal feeding damage.

Decisions to treat stink bug infestations are best made based on the percentage of bolls with evidence of internal damage (warts or stained lint associated with feeding punctures). To use this technique:

1. Remove about 10 to 20 bolls, 1 inch in diameter (about the size of a quarter), from each of the four parts of the field, avoiding field edges.

   

   Boll wall warts (Photo: Pat Porter)

2. Break open the bolls by hand or cut them with a knife. Look for internal warts on the boll walls and stained lint on the cotton locks.
3. Check bolls with visible external lesions first to determine if the internal damage threshold has been met, as bolls with external lesions are more likely to be damaged internally.

   

   Lint staining caused by stink bug feeding
   
   

 

Alternatively, detection of one or more stink bugs per 6 row feet can also be used as an action threshold.

South Plains Field Scout School

The South Plains Field Scout School is scheduled for the Friday, May 31, at the Hale County Texas A&M AgriLife Extension Office (225 Broadway, Plainview). There is no fee, and preregistration is not required. Registration begins at 8:30 AM with the program starting at 9 AM. Content will include classroom and hands-on training. Topics covered will include cotton agronomy, plant mapping, identification and symptoms of insect pests, plant d

iseases, and weeds.

Texas High Plains cotton: watch out for thrips

We are going to see most of our cotton emerging from the ground over the next week or so. I am seeing swarms of thrips coming out of drying wheat and other vegetation, which will be moving into cotton. It is important growers start thinking about thrips management if they haven’t already. Insecticide seed treatments such as imidacloprid still work in our region where thrips species composition in seedling cotton is mainly comprised of onion thrips and western flower thrips. 
There has been a decent amount of soil moisture to start with this season, which should help the activation and absorption of seed treatments little better. Seed treatments usually run their course by the second true leaf stage, requiring a foliar application under high-pressure scenarios such as in the northern regions of the South Plains and the Northern High Plains. The presence of immatures (wingless) is a good indicator of seed treatment not being sufficient. Rarely do we need two over-the top-applications for thrips, but there have been situations in the past where a second application was needed, especially in the northern counties. Our action threshold for thrips is one thrips per true leaf on an average in non-ThryvOn cotton. 

Thrips injury to seedling cotton

ThryvOn cotton does not need additional control measures for thrips. Field trials conducted throughout Texas have demonstrated that ThryvOn has excellent activity on all commonly encountered early-season thrips species, including western flower thrips and onion thrips. Adult thrips may still be found in ThryvOn cotton, but they do not feed as much or reproduce. The fact that fewer eggs are laid results in a great reduction in immature thrips in ThryvOn cotton. Our research indicates that ThryvOn cotton does not economically benefit from additional thrips control delivered from foliar insecticides.

As far as foliar insecticide choices are concerned for non-ThryvOn cotton, acephate at 3 to 4 oz/a still works well in our region, and so does Bidrin. Bidrin does provide a bit longer residual activity and is more rainfast than acephate. We had included Intrepid Edge in last year’s trials. This product offers a different mode of action, but its performance at the 3 fl oz/a rate was not necessarily any better than acephate.

Many of you must have heard of EPA’s interim decision to ban acephate uses in agriculture. It is one of the most widely used insecticides in cotton for the management of various insect pests, including thrips, cotton fleahopper, plant bugs, and stink bugs. The 60-day comment period is open until July 1. I would encourage folks to submit their thoughts on the EPA’s website.

Click here to access our cotton insects guide