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Friday, February 16, 2024

ThryvOn Cotton 101

WHAT IS THRYVON™ COTTON?

ThryvOnTM is a cotton biotechnology trait that expresses the Mpp51Aa2 protein (also known as Cry51Aa2). Unlike other Bt proteins used in cotton, this particular Bt protein does not affect caterpillar pests like bollworms. However, it has activity on thrips and plant bugs.


HOW DOES THRYVON TECHNOLOGY AFFECT GROWERS’ THRIPS MANAGEMENT DECISIONS?

ThryvOn cotton provides excellent control of thrips and eliminates the need for additional insecticide inputs. Against thrips, ThryvOn provides protection by deterring feeding and oviposition (egg-laying). Thus, adults may still be readily found in ThryvOn cotton, but they will not be feeding as much, or laying eggs, and will be repelled. The fact that fewer eggs are laid results in a great reduction in immature thrips. Comprehensive field trials conducted throughout Texas have demonstrated that ThryvOn has excellent activity on all commonly encountered early-season thrips species, including tobacco thrips, western flower thrips, eastern flower thrips, and onion thrips.

Data collected by Texas A&M AgriLife Extension has demonstrated that ThryvOn cotton does not economically benefit from additional thrips control delivered from insecticide seed treatments, in-furrow insecticides, or foliar insecticides. ThryvOn cotton not treated with these insecticide treatments may exhibit slightly more damage from thrips feeding, but the damage is very superficial and is not economically significant. In essence, ThryvOn cotton should not need additional control measures for thrips. However, seed treatments or in-furrow insecticides may still be desired for aiding in the management of wireworms, nematodes, or other early-season pests.


ARE INSECTICIDE SEED TREATMENTS OPTIONAL IN THRYVON COTTON?

Yes and no. While current research has documented limited benefits of adding insecticide seed treatment to ThryvOn, the seed will be marketed only with an imidacloprid seed treatment in the eastern half of Texas, where tobacco thrips are the predominant early-season thrips pest. Insecticide seed treatment is optional in the western half of Texas (Fig. 1). The reason for requiring insecticide seed treatment in the region of the state where tobacco thrips are common is for resistance management. The risk of tobacco thrips developing resistance to ThryvOn is considered higher than for other thrips species.

Fig. 1. ThryvOn cotton seed planted in the counties highlighted in blue will only be sold with the addition of an insecticide seed treatment, whereas an insecticide seed treatment will be optional for the red counties.

HOW EFFECTIVE IS THRYVON ON TARNISHED PLANT BUGS?

Although the Bt protein expressed in ThryvOn cotton has activity on tarnished plant bugs, it primarily offers suppression. ThryvOn has little known activity on adult plant bugs, but it can kill small nymphs. Thus, plant bug populations should not develop as quickly in ThryvOn as in non-ThryvOn cotton. However, insecticide applications targeting plant bugs may still be required. Currently, Texas A&M AgriLife Extension recommends utilizing the same action thresholds for plant bugs in ThryvOn cotton as for non-ThryvOn cotton but anticipates fewer insecticide applications being necessary.


DOES THRYVON HAVE ANY ACTIVITY ON COTTON FLEAHOPPERS?

ThryvOn cotton is not labeled for managing cotton fleahoppers. However, data collected by Texas A&M AgriLife Extension has demonstrated that ThryvOn has activity on cotton fleahoppers, similar to that observed for tarnished plant bugs. ThryvOn cotton will be readily colonized by adult cotton fleahoppers, but fewer large nymphs will survive. Furthermore, the authors have observed that ThryvOn does affect cotton fleahopper feeding behavior, which results in less cotton fleahopper-induced square loss. Thus, when cotton fleahoppers are present, ThryvOn cotton tends to have better square retention relative to non-ThryvOn cotton. Currently, Texas A&M AgriLife Extension recommends utilizing the same action thresholds for cotton fleahoppers in ThryvOn cotton as for non-ThryvOn cotton. However, data suggests that cotton fleahopper management with insecticides in ThryvOn cotton will be superior to non-ThryvOn cotton.


WHAT ABOUT THRYVON’S ACTIVITY ON OTHER COTTON PESTS?

The Mpp51Aa2 protein in ThryvOn has no known activity on caterpillars, stink bugs, aphids, or whiteflies. However, it is unknown whether this technology will impact mid- to late-season thrips species, such as chili thrips, bean thrips, or Kurtoma thrips. Additionally, it is unknown if ThryvOn has activity on cotton pests similar to plant bugs, such as the verde plant bug or the rapid plant bug. Efficacy data on these pests has yet to be collected.


DOES THE THRYVON TECHNOLOGY HAVE ANY IMPACT ON BENEFICIAL ARTHROPODS?

ThryvOn has little impact on the most beneficial arthropod species. The Mpp51Aa2 protein has been shown to have some activity on minute pirate bugs in that it delays their development. Also, it does affect thrips, which are often important predators of spider mites.


ARE THERE ANY UNEXPECTED RISKS FROM PLANTING THRYVON COTTON?

Because ThryvOn has very good activity on thrips and thrips are effective predators of spider mites, it has been observed, but not quantified, that spider mite outbreaks may be more likely in ThryvOn cotton than in non-ThryvOn cotton. However, more research is necessary to better understand the magnitude of this risk.


HOW WOULD THRYVON HELP WITH OVERALL CROP MANAGEMENT?

ThryvOn does offer some management flexibility to growers. Managing insecticide applications across a large span of farmland with limited equipment can pose timing challenges. Weather conditions can exacerbate this issue. ThryvOn offers growers a level of flexibility, enabling them to undertake certain activities that were previously unattainable under such circumstances. For instance, during a cool and damp period in the initial stages of the growing season, maneuvering a sprayer across the cotton field might be unfeasible despite the presence of thrips actively feeding. However, with the inherent thrips protection integrated into ThryvOn cotton, growers would not have to worry about this issue. Another advantage of the built-in protection is the elimination of concerns related to chemical wash-off problems and potential insecticide loss due to heavy rainfall events.


DOES THRYVON COTTON NEED A DIFFERENT PLANT GROWTH REGULATOR (PGR) REGIMEN THAN NON-THRYVON COTTON?

Overall, ThryvOn cotton exhibits better fruit retention than non-ThryvOn varieties, which can affect plant growth and maturity. Thus, although the ThryvOn trait in itself does not warrant a different PGR regimen, better square sets may reduce the need for some PGR applications.


DOES THRYVON OFFER GREATER ECONOMIC RETURNS THAN THE NON-THRYVON COTTON?

The economic benefit from planting ThryvOn cotton is dependent upon the pest pressures of thrips, tarnished plant bugs, and cotton fleahoppers. If these pests are not common issues on a particular farm, there is probably little benefit from planting the technology. However, eliminating the need for an insecticide seed treatment or foliar insecticides can provide tangible benefits. In general, if the cost of one insecticide application can be realized on ThryvOn, the cost of the technology will easily pay for itself.


THRYVON TAKE-HOME POINTS

ThryvOn Bt technology has excellent activity on thrips and eliminates the need for supplemental thrips control measures. This technology will aid in managing plant bugs and cotton fleahoppers. Though it will not eliminate the need for insecticides to manage these pests, it may reduce the number of insecticide applications necessary. Timely field scouting, use of action thresholds, and insecticide selection are still important for plant bug and cotton fleahopper management in ThryvOn cotton. Finally, ThryvOn cotton has no efficacy on insect pests, such as aphids, spider mites, grasshoppers, stink bugs, etc., and therefore, regular field scouting and monitoring is still critical in ThryvOn cotton.


Authors: Suhas Vyavhare and David Kerns; Extension Entomologists, Texas A&M AgriLife Extension Service


Monday, February 12, 2024

Consider using preventative insecticide seed and at-plant treatments to manage wireworms in cotton

Wireworms are a common pests of seedling cotton across the High Plains and Rolling Plains regions of Texas. Increased wireworm abundance over the last decade or so is partly due to reduced use of broad-spectrum insecticides such as aldicarb (currently available under the trade name AgLogic) and to some extent due to the increased adoption of cover crops and conservation tillage practices in the agricultural landscape. All wireworm species, including true (larvae of click beetle) and false (larvae of darkling beetle) wireworms, inflict damage as worms or immature stages that live exclusively underground. One genus of darkling beetles i.e. Blapstinus, however, can also cause damage as an adult. Often, during drier years, these beetles (~1/4 inch long) migrate from nearby grasslands, and fallow fields to cotton and cause damage by chewing on stems of young and tender seedlings at or slightly below the soil surface.

The incidence of wireworm is more severe in fields with known history of its infestation, those followed by grain crops such as sorghum and wheat, and the fields planted with no insecticide seed treatments. In my observation, wireworm infestation and injury level tend to be much higher in fields that are planted with untreated seed consecutively for more than two years. Although there are no insecticide seed treatments that are specifically labeled for wireworms in cotton, those used for other early-season insect pests such as thrips (e.g. neonicotinoids) do offer some level of wireworm suppression.

There are no rescue treatments for wireworms. Therefore, it is critical to make sure that you are getting a seed treatment package that has the full rate of insecticide (e.g. imidacloprid). Although almost all commercially available cotton seeds come treated with fungicide, they would not necessarily be treated with an insecticide. In addition, some companies have insecticides applied to seeds at a very low rate to protect seeds from storage pests. Such treatment at storage rate will not provide any control against pests in field condition. Different companies provide different combinations of fungicide, insecticide and nematicide active ingredients in their seed treatment product portfolio and it is important that you pay close attention to what you are getting when you opt for a certain package. For instance, under Acceleron brand (Bayer CropScience), the basic treatment (Acceleron Basic) comes with no insecticide, while the Acceleron Standard and Acceleron Elite both have imidacloprid (0.375 mg ai/seed) as an insecticide component. Similarly, BASF offers their Core Seed Treatment Package with imidacloprid at only storage rate (4.7 oz/ 100 lbs seed) and to get the full rate of imidacloprid (0.375 mg ai/seed or ~11 to13 oz/100 lbs seed), you need to get their Prime Seed Treatment Package. Whatever brand of seed you choose, if you are considering seed treatments for managing early-season insects, make sure the seed treatment package you select has a full rate of insecticide active ingredient.

In addition to seed treatment, I would also suggest using at-plant treatments such as in-furrow application of Admire Pro, AgLogic, or pyrethroids (e.g. bifenthrin) in fields where wireworms have been an issue in the previous year/s. These products are labeled for use in cotton for early-season insect pests such as thrips and aphids and have wireworm activity. Considering the long life cycle of these worms (3-4 years), it is very likely that they will be there for next season if were present in the past.   

Table. 1. Insecticide ingredients of selected seed treatment packages in cotton.

Company

Cotton Seed Brand

Seed Treatment Product Trade Names

Insecticide Active Ingredient (at standard rate)

 

Bayer CropScience

DeltaPine

Acceleron Basic

none

 

 

Acceleron Standard

imidacloprid

 

 

Acceleron Elite

imidacloprid

BASF

FiberMax, Stoneville

Core Seed Treatment Package

none*

 

 

Prime Seed Treatment Package

imidacloprid

Corteva AgriScience

PhytoGen

PhytoGen TRiO

imidacloprid

Americot

NexGen

CottolyST Base

none

 

 

CottolyST IMI+

imidacloprid, acephate

 

 

CottolyST Enhanced

imidacloprid, acephate

 

 

CottolyST Premier

imidacloprid

Syngenta

 

Avicta Elite Cotton

imidacloprid + thiamethoxam

*imidacloprid at storage rate

 

Darkling beetle, Blapstinus sp. (photo: Pat Porter)

Wireworms (photo: Pat Porter)


Wednesday, May 3, 2023

Wireworms: a threat to stand establishment in the High Plains cotton

 As we approach the planting season, one of the first groups of insects that we need to start thinking about are wireworms. Wireworm issues are on the rise with increased adoption of conservation tillage practices and potentially the reduced use of aldicarb, a broad-spectrum insecticide over the last decade or so. Although cotton is not a preferred host for wireworms, they still can inflict serious damage to cotton seedlings especially in fields following grain crops.

What are wireworms?

Fig. 1. Click beetle (photo: Mike Quinn)
There are two types of wireworms. True wireworms are larvae of click beetles (Fig. 1) (Family: Elateridae), while false wireworms are larvae of darkling beetles (Fig. 2) from the Tenebrionidae family. Adults are highly variable in size and shape from species to species. Larvae (Fig. 3) in general look alike and are difficult to distinguish. They are smooth skinned, elongated, cylindrical, and up to 1¼ inches long. They are creamy white to yellow or light brown. Their heads are typically darker, and they have small true legs clustered near the head.



Wireworms (photo: Pat Porter)


Darkling beetle (photo: Mike Quinn)







What is the nature of wireworm injury/damage?

The larvae damage cotton by feeding on the root, hypocotyl (stem of the germinating seedling), and cotyledon (seed leaves) of emerging plants (Fig. 4). Root feeding can kill plants but usually results in stunting. The most severe damage occurs when the hypocotyl is severed, killing the plant, and reducing the stand. The larvae also feed on the growing point of the plant, slowing the growth of the main stem.

Wireworm injury to cotton seedlings (photo: Pat Porter)

 Are certain fields at higher risk of wireworm injury?

In general, fields with continuous vegetation cover allow more wireworms to survive if they are present or the field has history of wireworms. Wireworm attacks on cotton tend to be most severe when the cotton is planted following grain crops (especially sorghum), weedy ground, or in reduced-tillage systems.

 Does cultural practices such as crop rotation help?

Soil tillage in late spring and late summer when larvae or eggs are in the upper soil layers to enhance their death by desiccation, mechanical injuries or predator exposure can help reducing the wireworm load. Crop rotation is ineffective due to a much longer life cycle (2-8 years depending on species) and broad host range.

How to monitor wireworms and is there an established threshold?

Wireworms are difficult to monitor as larvae are strictly soil-dwellers and not seen unless removed from the soil. After planting, inspect emerging plants for any visible chewing damage to roots and stem and monitor the plant stand. There are no rescue treatments for wireworms, but regular field scouting will help make timely re-plant decisions based on the extent of stand loss and the size of skips.

Bait trapping a few weeks prior to planting can help monitor wireworms. Although the results of this technique have been inconsistent, it can help detect the presence of wireworms. To do this, dig several holes the size of a softball and fill them with soaked wheat or oats. Cover the hole with soil and examine the baited holes after about a week to determine if wireworms are present.

 What are the management options for wireworms?

There are no rescue treatments. Foliar insecticides targeted at adults are rarely needed. However, if adults are present in large numbers, causing evident plant clipping and probable unacceptable stand reduction, foliar insecticide application can be made. Treat wireworm larvae preventively. Insecticide (e.g. imidacloprid, thiamethoxam) seed and at-plant treatments are the most effective means of minimizing wireworm damage.

 Where to look for more info on wireworms?

Checkout our fact sheet on wireworms

Short video on wireworms

Assessing wireworm damage

 

Monday, February 13, 2023

The 2023 Version of the Handy Bt Trait Table for Corn is Posted

The new and revised 2023 version of the Handy Bt Trait Table for US Corn Production has been posted. Two of the seed companies are changing the names of their product lines this year, and the table now includes the new and old names. We chose to continue listing the older Bt products that have been removed from the market, in part so people can go back to older planting records, seed guides and research results. 

More hybrids from different companies now have the RNAi product dvSnf7 added to rootworm Bt corn, and this is reflected in the table. We have expanded the herbicide tolerance column to reflect the new Enlist technology.

Expansion of the table meant that we had to go to two pages to list everything, but the good news is that the font is larger!

Pat Porter

Friday, February 10, 2023

Managing insects in ThryvOn cotton

 Suhas Vyavhare and David Kerns

We have had a few inquiries around ThryvOn technology in cotton which has recently been fully commercialized in the US.

What is ThryvOn?

ThryvOn is a genetically engineered cotton expressing Bacillus thuringiensis (Bt), toxin mCry51a2. This protein has insecticidal activity (mostly deterrence/repellency) against thrips and plant bugs. Cry51 has an excellent activity on thrips. Field research indicates that ThryvOn cotton will not need insecticidal seed treatment (e.g., imidacloprid) or a foliar insecticide application for thrips in cotton. We do find adult and immature thrips in ThryvOn cotton but significantly fewer than the non-ThryvOn and with little or no injury to seedlings.

What would be the recommendation for thrips control in ThryvOn cotton?

We do not recommend insecticide treatment for thrips in ThryvOn cotton. Seed treatment (imidacloprid) will be optional when purchasing seed in West Texas but not in the East region where ThryvOn is packaged with insecticidal seed treatment. Contact your seed rep for more info on seed availability and seed treatment options.

How good is it on Lygus bug?

Not as dramatic as it is on thrips. There seems to be little or no activity on adults, but overall, there would be fewer and relatively smaller nymphs in ThryvOn cotton compared to the non-ThryvOn. Plant bug populations develop relatively slower in ThryvOn cotton which will provide some flexibility in terms of crop management (e.g., product choice, application timing) but will not necessarily eliminate the need for foliar application. Until we have a better understanding on ThryvOn on plant bugs, we are recommending following the current action threshold for plant bugs in both ThryvOn and non-ThryvOn cotton. Plant bug thresholds are based on combination of insect numbers and the level of fruit retention.

Does it have any activity on cotton fleahopper?

Cotton fleahopper will not be included on the ThryvOn label as a target pest. However, bioassays conducted by Bayer suggest mCry51Aa2 has activity on cotton fleahopper. Research conducted by Dr. David Kerns at Texas A&M indicates that ThryvOn cotton exhibits some activity on cotton fleahopper under field conditions and in cage studies, and slightly reduces the number of large nymph survival. However, these effects will most likely not prevent the need for foliar insecticide applications. Although cotton fleahopper numbers may not vary much between ThryvOn and non-ThryvOn cotton, ThryvOn cotton has consistently shown better square retention than non-ThryvOn at varying levels of cotton fleahopper infestation. Similar to Lygus bugs, we are recommending treating cotton fleahoppers in ThryvOn cotton using our current action threshold.

Does this technology have any impact on beneficial insect populations?

Considering the relatively broad-spectrum activity of mCry51Aa2 compared to the older Bt proteins in cotton, this is a concern among several. We have not noticed any negative impact on the beneficial populations that will affect the natural control at field level. Research conducted by Bayer indicated that mCry51Aa2 is unlikely to pose much risk to a number of beneficial insects in cotton including lady beetles, lacewings, minute pirate bugs, big-eyed bugs, damsel bugs and assassin bugs. Thus, we anticipate any impact on beneficial insects will be little to none.

In summary, ThryvOn is yet another tool in the toolbox that will further improve insect pest management in cotton. It will reduce the insecticide applications targeted at thrips and maybe to some extent against plant bugs. Regular field scouting, however, still remains critical to monitor plant bugs and other insects to make timely management decisions.  

Tuesday, August 23, 2022

Managing late-season insects in cotton

 As we approach the end of August, one question that has been received lately more often than any other is at what stage do I stop worrying about insects in cotton?  

The major insect activity that I am noticing in South Plains cotton at this stage is around lygus bug and stink bug.  

Stink bugs, on the other hand, will have to be scouted for a bit longer. Although they favor medium-sized bolls, they can feed on any size bolls. Stink bugs may feed on bolls 25 or more days old; bolls of this maturity are relatively safe from yield loss. In larger bolls, stink bug feeding often results in dark spots about 1/16 inch in diameter on the outside of bolls. These dark spots do not always correlate well with the internal damage—callus growths or warts. Once the cotton reaches 450 DD60 beyond 5NAWF, sampling and treating for stink bugs may no longer be necessary since bolls produced after this point will not become fully mature or contribute significantly to the crop yield. Now, it is possible that this value may shift slightly due to factors such as boll shedding, variety, irrigation, presence of pathogens (e.g., boll rot).  Action threshold for stink bugs is based on percentage of bolls with internal injury. For instance, the stink bug threshold during 5th, 6th, 7th, and 8th week of bloom is 10% 20%, 30%, and 50% internal boll damage (lint staining, boll warts), respectively.

Link to updated cotton insects guide: https://lubbock.tamu.edu/files/2022/07/managing-cotton-insects-in-texas.pdf

Thursday, July 21, 2022

Update on the Mozena leaf-footed bug in Texas High Plains cotton

 Suhas Vyavhare and Kerry Siders

Leaf-footed bug, Mozena obtusa (fig. 1) is being spotted on a variety of plants across the Texas High Plains. We have gotten a few inquiries about how damaging this insect is to cotton and what insecticides would be most effective. In cotton, we have spotted this insect in multiple counties across the South Plains region. The numbers remain very low in all the fields where we have seen it except one field in Hockley County where it was found to infest cotton in large numbers (15-20 immatures/plant). In this particular field, insects appeared to be moving from the adjacent fallow field with mesquite trees which are preferred host of Mozena bug. Even the immature stages of this insect are quite agile and can travel some distance in search of new hosts. Fig. 2 shows results from the insecticide efficacy trial being conducted near Sundown, TX. Data collected at 3 and 7 days after treatment application indicate pyrethroids to be the most effective insecticides. We are also collecting data on the impact of Mozena bug on square retention in cotton. Thus far, we have not observed any square loss that can be attributed to this insect. Overall, square retention across the trial area remains over 90%.

Fig. 1. Mozena obtusa adult and nymphs
We are beginning to notice a few egg masses and small immatures on cotton plant indicating its suitability as a host for Mozena bug. With the absence and/or reduction in the availability of preferred hosts such as mesquite and other legumes, this leaf-footed bug can become an issue in cotton. Leaf-footed bugs in general prefer to feed on fruits and seeds and therefore their populations need to be monitored closely as our crop enters the boll development phase.  I would treat them more like stink bugs which feed in the similar manner with their piercing and sucking mouth parts and are mainly boll feeders in cotton. When scouting fields monitor both insect population density and the extent of damage to the crop (fruit retention, external and internal boll injury) and base the treatment decisions accordingly.

Here is a link to our recently updated cotton insect management guide: https://lubbock.tamu.edu/files/2022/07/managing-cotton-insects-in-texas.pdf

  

Fig. 2. Insecticide efficacy against leaf-footed bug, Mozena obtusa in Texas South Plains cotton. Means showing the same letter are not significantly different [Tukey’s HSD; P = 0.4226 (3 days after treatment (DAT)); 0.0302 (7 DAT)].

*Insecticide products were evaluated for research purpose only. When using an insecticide read and follow label directions for safety precautions, rates and preharvest intervals.