Phaseout of Most Bt Corn Hybrids Proposed

 My recent post discussed the proposal by EPA to drastically change the resistance management regulations around Bt corn and cotton. You can submit a comment here before November 9th. The proposal is hard to find on the EPA website, so I have reposted it here.  Part of the plan is to phase out all single toxin Bt corn hybrids within three years, and all pyramid (multi-toxin) hybrids that do not contain Vip3a within five years. 

Assuming we don't get any wonderful new technology in the next few years, this would leave southern corn growers with two choices; grow a pyramid hybrid that had Vip3a, or grow non-Bt corn. (It would also leave cotton growers with just the 3rd generation varieties containing Vip.) There are some implications for resistance management of corn earworm/cotton bollworm that are being discussed should this come to pass, like having all Bt corn and Bt cotton in the south expressing Vip, while at the same time the older toxins are failing and less able to provide any protection against resistance developing to Vip in the pyramid with older toxins. Essentially, Vip would become a single toxin because the pyramid could not protect it. The same EPA proposal is attempting to fast-track the removal of old single toxin corn hybrids because they pose a very clear danger for resistance evolution. I explained why this is so back in 2018.

Another outcome would be that corn growers would have a drastically shortened list of hybrids from which to choose. The EPA proposal simply listed the hybrids to be removed by their registration numbers, which is regulatory-speak and rather foreign to most of us. However, yesterday, Emily Unglesbee at DTN/Progressive Farmer posted an article that put common names on these corn and cotton hybrids. The title of the article is Bt on the Chopping Block, and I encourage you to read it. 

Chris DiFonzo at Michigan State University is lead author of our "Handy Bt Trait Table For US Corn Production", and she has created a new table that shows what will be left for caterpillar control after the proposed phaseout. Here is a pictorial representation of the bottom line.

The 8 survivors. 

The 34 types of Bt corn currently sold.

The Handy Bt Trait Table will give you a high resolution view of hybrids currently sold. 

Tighter Regulations Around Bt Corn Are Pending

This week the EPA released a draft plan that essentially overhauls many of the regulations around insect resistance management (IRM) in Bt crops grown in the "cotton belt". 

There are many major changes proposed, one of which is that field failures are presumed to be cases of "practical resistance" if certain criteria are met. (Like 6% boll damage in third generation (Vip) cotton and second instar bollworm larvae are present, which is basically the treatment threshold we use now.) Seed companies can then make collections and do the insect rearing and testing to refute the determination of resistance, if they want to do so. This is totally opposite of the way things have been done for 25 years. In the past, field failures were presumed to be from susceptible insects, and only laboratory testing could determine whether the insects were resistant. 

Seed blend corn refuge will be approved for southern planting. However, a 20% structured (block) refuge will also be required with fields planted to seed blends. This block refuge is basically insurance until we can figure out whether seed blends are a good thing or a bad thing, as some of the data say they might accelerate resistance. In the last four years there has been an all out effort by the seed industry and Land Grant Universities to answer this question, and if it turns out that seed blends are safe then the requirement for a block refuge could be dropped in the future. ABSTC (the Agricultural and Biological Stewardship Technical Committee, a consortium funded by Bayer, Corteva (Pioneer) and Syngenta), sponsored a very expensive and detailed seed blend trial that Dr. Suhas Vyavhare and I conducted near Olton this year. Bayer sent a large crew of people to help on the days we could not possibly have done all of the work ourselves. I am grateful that Bayer and their excellent people stepped in at their own expense to help us answer this important question; we could not have done it without them. We are all trying to answer the seed blend questions as quickly as possible. 

The new rules, if enacted as currently proposed, will change things at the farm level. I am quoting from the document directly.

• "Sales of Bt corn products requiring block refuges must be followed up with on-farm visit by the seed industry for compliance monitoring by ABSTC during the growing season. This will be conveyed to growers at the point of sale and be included in the grower agreement. Visits will be reported to the Agency [EPA].
• For farmers out of compliance with block refuge standards in the cotton belt for one year, the registrant [seed company] will withhold all the company's Bt corn products, including RIB and block refuge for two years.
• Registrants must ensure that seed dealers obtain signed grower agreements that set forth the terms of the IRM program. If a seed dealer fails to ensure that at least 95% of the customers sign grower agreements, registrants will restrict the availability of the Bt seed to that dealer. Registrants must ensure that seed dealers keep a record of signed grower agreements for a period of at least three years from sale. 
• Industry must ensure availability of non-Bt elite corn hybrids for refuge."

Why is EPA doing this? Basically it is because corn earworm/cotton bollworm is now resistant to all but one Bt toxin, Vip3a. Refuge rules were not well followed in the past, and now resistance has come home to roost. If we are to prevent resistance to Vip3a, the last effective toxin for bollworm, things need to change. Prior to this we were operating under the set of rules mostly set forth in 1996, and there were some major problems with them. The new guidelines correct several of the mistakes made in the past.

The EPA document is not final, and in several places it goes out of the way to ask for input from producers and consultants. I know the woman who wrote the document and is in charge of changing it, and she sincerely wants to hear from you on how these proposed changes will affect you, and whether there is a better way to accomplish the objectives. I trust her to listen to you. You can be assured that the anti-Bt crop lobby will be submitting comments, so here is your chance.

The 24-page draft document is here: https://beta.regulations.gov/document/EPA-HQ-OPP-2019-0682-0007. The docket where you can submit your comments is here: https://beta.regulations.gov/search?filter=EPA-HQ-OPP-2019-0682. I would be glad to answer any question about the proposed changes, and you can write me at p-porter@tamu.edu. 

Pat Porter

Bollworms per acre coming off of corn (or why we had fewer bollworms this year)

Dr. Suhas Vyavhare and I are conducting a very detailed experiment this year on some aspects of Bt corn. Part of the experiment involves putting 120 emergence cages on the ground under corn after corn earworm larvae (cotton bollworms) have left the corn ears and entered the soil for pupation. This lets us determine the number of moths being produced per square foot or acre under actual field conditions. After they emerge as moths, these insects will then fly to other crops, and their eggs become the late season bollworm infestations in cotton and headworm infestations in sorghum. 

2020 was a fairly light year for corn earworm infestation in corn; only 54% of the ears were infested with larvae at our Olton trial. In most years this would have been nearly 100%.

Here is the math: 

This year we had 3,398 moths emerging per acre from irrigated non-Bt corn, or 407,760 moths per 120 acre field.

In a "normal" year when almost every ear had a corn earworm, this would have been 6,292 moths per acre, or 755,040 moths per 120 acres of irrigated corn. 

My work with the older Bts like Cry1Ab, Cry2Ab2, Cry1F and Cry 1A.105 suggest these Bts are no longer killing as many earworms as they once did, so one could expect them to produce a significant number of moths. Vip3a corn is highly effective at killing corn earworm, so it will not contribute significantly to a moth flight (until we get resistance). 

This is the first chance we have had to estimate the number of cotton bollworm moths coming off of corn on the High Plains, and the numbers are impressive, at least in their contribution to localized bollworm populations in nearby cotton. The lower number of bollworms this year in cotton seem to be directly linked to the lower number of bollworm moths that laid eggs in corn. 

Sesame Leafroller Now Widespread on the High Plains

Sesame leafroller is a major pest of the crop, and we have tracked its movement north this year. This is a new pest for us. Dr. Emi Kimura, our agronomist in Vernon, reported it last week. This week Drs. Qingwu Xue and Jourdan Bell reported it at Bushland, and one of our superb Independent Crop Consultants reported it at Abernathy just north of Lubbock and made comment that he treated the field three weeks ago and now had to treat again. He also just today reported it near Gruver in the northern Panhandle.

Dr. Holly Davis, Extension Entomologist in Weslaco, recently posted a nice blog article and video on sesame leafroller, so I won't duplicate that information here. She conducted an insecticide efficacy trial which showed pyrethroids don't work all that well. She also found that the 8 oz and 12 oz. rates of Prevathon worked very well, and the 8 oz rate did just as good a job. (The difference will be that the 12 oz rate will provide longer residual control.) Blackhawk also worked very well at 1.1 and 2.2 oz, but Blackhawk is not labeled for use on sesame. 

Here are some photos from near Abernathy today.

South Plains cotton: questions related to Lygus bug

 At what stage cotton is safe from Lygus bug?

No treatment is needed once cotton reaches 350 DD60s beyond cutout (5 NAWF).  

 What is the threshold for Lygus bug after peak bloom?

Use of drop cloth is the best way to measure plant bugs after peak bloom. Treatment thresholds based on drop cloth sampling is 4 to 6 Lygus bugs per 6-foot row.

 What insecticides to use to manage lygus bug in cotton?

Below is a table with the list of suggested insecticides. Add Transform to the list.

 

Would these products provide control against stink bugs too?

Acephate and Bidrin has a good activity against stink bugs. However, other plant bug products alone (e.g. Transform, neonicotinoids) will only provide some level of stink bug suppression and will not be enough to effectively control them.

Tip: Do not confuse seed bugs or scentless plant bugs with Lygus. Although fairly common, scentless plant bugs feed mostly on weeds and are harmless to cotton.  

 

Lygus bug (photo: Pat Porter) 

Scentless plant bug 

Texas High Plains cotton: stink bug remains quiet

Cotton fields that have accumulated 450 DD60 (degree days 60) beyond cutout (5NAWF) are generally safe from an economic damage from stink bugs. Late planted and heavily irrigated fields with fairly high number of young bolls still need to be scouted for stink bugs. Stink bug feeding on young bolls (<10 days old) usually causes the bolls to shed. In larger bolls, stink bug feeding often results in dark spots ~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 and stained lint. Damage to the internal boll wall is a good indication that lint and seed are affected.

Base decisions to treat for stink bug infestations on the percentage of bolls with evidence of internal damage (warts or stained lint associated with feeding punctures).  To use this technique: ◆ Remove about 10 to 20 bolls, one inch in diameter (about the size of a quarter), from each of four parts of the field, avoiding field edges. ◆ 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. ◆ Check bolls with visible external lesions first to determine if the internal damage threshold has been met because bolls with external lesions are more likely to also be damaged internally.

Use a 10 percent to 15 percent boll injury threshold during weeks 3 through 5 of bloom and 20-30 percent during weeks 6 or later of bloom. If using drop cloth or whole plant inspection method, detection of 1 stink bug per 6 row-feet would also justify treatment. Pyrethroids or organophosphate (e.g. Bidrin, Orthene) insecticides provide a good control against conchuela stink bug which is the primary species we encounter. Products targeted at plant bugs such as Transform, Carbine, Diamond, and neonicotinoids will not be sufficient to control stink bugs. For the mix of stink bug and plant bugs, either Bidrin or acephate would be a good choice or a tank mix of plant bug product (e.g. Carbine, Diamond, Transform, neonicotinoids) and a pyrethroid or acephate. Detailed list of suggested insecticides can be found at: https://lubbock.tamu.edu/files/2019/08/2019-Cotton-Insect-Control-Suggestions_ENTO090.pdf

Texas High Plains cotton: keep an eye out for bollworms

The current spike in bollworm moth activity in our pheromone traps is from moths coming out of corn. These moths pose a substantial threat to cotton with majority of our fields being in peak bloom. I have not noticed significant worm activity in cotton yet but last week we did start to pick some worm damage in our research plots of non-Bt cotton. The amount of fruit damage in non-Bt cotton ranges from 0-2%. This is expected to increase over the next few weeks as more moths coming out of corn land in cotton. It is important to scout cotton twice a week irrespective of Bt technology. Bt resistance in bollworm field populations being widespread, under high insect pressure we may need to spray some of our two-gene Bt fields. In all cotton (Bt or non-Bt), treatment is recommended if 6% fruit damage (mix of squares and bolls) is observed.

The diamide insecticides, Besiege (7-10 fl oz/acre) or Prevathon (14-20 fl oz/acre), are the most effective products to control bollworm. These products provide about two weeks of residual control. With higher rate, longer residual control can be obtained. If you are finding stink bugs as well, Besiege will provide control against both worms and stink bugs. However, if there are no stink bug issues, it is best to avoid unnecessary pyrethroid applications as they can flare up aphids.  

 List of additional insecticide options can be found in our cotton insect management guide: https://lubbock.tamu.edu/files/2019/08/2019-Cotton-Insect-Control-Suggestions_ENTO090.pdf

 Here is a link to our video on how to scout for bollworms: https://www.youtube.com/watch?v=ELcza4t2BYI

 

Sugarcane Aphid in Lubbock and Hale Counties (Probably Crosby and Floyd, Too)

I found sugarcane aphid colonies on post-flowering sorghum today at the Experiment Station in Lubbock. An independent crop consultant reported to Blayne Reed this afternoon that he had just found some in Hale County, about 6 miles northwest of Abernathy. So here we go.

In the last few years we have tracked the aphid's arrival on the southern High Plains, and traditionally it comes first through Floyd and Crosby counties, then to Lubbock, Hale etc. So it is most likely that Crosby and Floyd counties have it as well.

There is some good news: The aphid is a couple of weeks late in arriving, and many fields will be able to outrun it. And in what is really good news, we are not getting large flights from the south and southeast, so the invading population is relatively small, which gives the beneficial insects the upper hand for now.

I have been asked about the 106 - 108 degree days, and whether these will phase the aphid. I don't know. Drought stressed sorghum loses the ability to transpire in the hot part of the day, which means it does not have much evaporative cooling going on at the leaf surface. On days like we had today, I can easily see it being 120 degrees near the soil surface in full sunlight, and this is hot enough to affect some types of insects. Irrigated sorghum is less apt to shut down on these hot days, so it will continue to have some evaporative cooling at the leaf surface. I don't think aphids on these plants will be affected much.

Texas High Plains Cotton: Time to Guard Up Against Thrips

Cotton planters are rolling across the Texas High Plains. While lot of cotton seed will go into the ground over the next couple of weeks, some of the early planted stuff is making its way above ground. Thrips are one of the first insect pests that we experience on seedling cotton. I am seeing thrips swarms all around and can find them on almost everything that is green. It will not be too long before these tiny insects land on the emerging cotton. We usually experience higher thrips pressure in the areas north of Lubbock. Under good growing condition, plants do recover from thrips injury without economic yield loss, but when additional stresses such as cold temperatures, sandblasting and or nematodes are present, thrips infestation can delay growth and reduce yields substantially.

Thrips species composition in the South Plains region is mainly formed by onion thrips (Thrips tabaci) and the western flower thrips (Frankliniella occidentalis). Preventive insecticide seed treatments provide a good control against these species for up to ~3 weeks after planting. However, this can vary with growing conditions and the weather. Almost all our in-furrow or insecticide seed treatments used are neonicotinoids (e.g. imidacloprid, thiamethoxam). Remember, these are water-soluble insecticide compounds that are taken up through the roots and translocated into growing leaf tissues and hence need enough soil moisture to be effective.

When scouting for thrips, there is truly no substitute for whole plant inspections from a representative sample from across the whole field. We may find adult thrips (winged) in almost every field but it is important to know that presence of adults alone will not warrant foliar insecticide application. The presence of immature thrips (wingless) is a good indicator of whether the seed treatments are still effective enough or not. The action threshold for thrips is one thrips per true leaf and our suggestions as rescue treatments include acephate, dicrotophos (e.g. Bidrin) or spinetoram (Radiant). Timing of insecticide application is critical. Research indicates that insecticide application beyond 1^st true leaf stage will not result in significant yield gains. Also, remember, it is not uncommon to see “look-a-like” thrips symptoms under our environment—beware of similar symptoms from sandblasting, residual herbicides and high temperatures before making spray decisions. We cannot control the environment or the market but we sure can save money and time by avoiding ill-timed or unnecessary insecticide applications.

"Murder Hornet" Facts and a Texas Perspective

The Asian giant hornet, Vespa mandarinia, is in the news after being found in Washington State. The media have taken to calling it the “murder hornet” because it does kill people. However, it is hard to find authoritative information on this insect, so we are linking to a new article written by Dr. Mike Merchant that describes the insect and discusses why it is indeed dangerous. It is not in Texas, and Dr. Merchant also discusses why it may not get here.

Giant hornets genuinely frightening (posted 5/5/20).

Sign up to get text notification of short weekly IPM audio updates

A few weeks ago I introduced the new IPM Audio Updates that we are producing. The IPM Agents strive to cover all the important news yet keep the broadcast under 10 minutes. The High Plains version features Blayne Reed, Kerry Siders, Dagan Teague and John Thobe. The Concho St. Lawrence version features Haley Kennedy and Brad Easterling. Pat Porter and Suhas Vyavhare will make cameo appearances as needed.

There are two separate broadcasts, one for the High Plains and one for the Concho St. Lawerence area. If you want both then sign up for each one separately. The signup page is here:  https://www.texasinsects.org/signup-texts.html. Once you are signed up, you will get a text message immediately after the weekly broadcast is completed and posted on our server.

There is not much fine print: We will never share your phone number or any other information with anyone. We don't ask your name, but we will ask whether you are a producer, consultant, ag industry, AgriLife or other. This so that we can get an idea of who is using the service. If you decide to stop getting the text messages, just text the word STOP to the number that is at the bottom of each text message. 

Join us for rapid updates on insects, weeds, diseases and growing conditions as we start the 2020 season. If you want to sample the broadcasts before signing up, the ones so far are here: https://www.texasinsects.org/southern-high-plains-pest-news.html. (Future recordings will be in stereo.)

Off Topic: COVID-19 Life in Lubbock and the Southern High Plains

The coronavirus restrictions have been in place for over one month now and there are 494 known cases in Lubbock County as of this writing, and relatively few in surrounding counties. When I look at how we as a people have handled this as compared to some other places I think it says a lot about us.

For example, a co-worker's mother was discharged from an assisted care facility three weeks ago, and on the way out the door the family was told a worker at the facility had tested positive for the virus. So what did the family do? They took their mother to their house where they could care for her and totally quarantined themselves for two weeks. They did not have to do it, they did it to protect others.

The great reopening will begin this week at the direction of our governor and local politicians. No one wants more virus cases, but many local businesses are on the brink and need to reopen, even if in a modified fashion. We are about to embark on a great experiment and the outcome is unknown. However, what I do know is that we are a unique people. The video linked below shows some of that. It contains some of my photos from over the years and was issued through 4th on Broadway, a group of volunteers that for 30 years has put on the 4th of July parade and largest free festival in the state with support from local businesses and individuals. The music is by Doug Smith, and his family graciously donated it when they learned about this project. I am deeply grateful for their gift, and to be living here on the southern high plains of Texas.

https://vimeo.com/406063736

Patrick Porter

Miller Moth Deluge Near

We had tons of army cutworm larvae in many of our wheat and alfalfa fields this spring. I have never used the word tons when trying to describe a quantity of insects, but here is some math. We recently conducted an insecticide efficacy trial on these larvae, and they averaged 7 per square foot. An acre would have 304,920, and a 50-acre field would have 15,246,000. We have many, many wheat fields that are infested this year. The larvae are now entering the pupal stage and will soon emerge as adults and invade our homes and structures. 

Army cutworm larvae from two plots in the efficacy trial.

They prefer to fly at night and seek shelter in the day, which is why you will get up one morning and find your porch covered, and more moths in the house if it is not sealed up well. Don’t leave your truck windows down either. Some people say that a bowl of water and a little dish soap can be left under a porch light. The moths come to the light and contact the water where the dish soap has eliminated the surface tension so the moths sink and drown. This is true, but it won’t really reduce the number of moths to any degree, although the revenge factor might make you feel better. Revenge might be on your mind because the two biggest complaints about the moths are that they keep people from sleeping because of all of that flying around in the bedroom while they are trying exit the house, and because the oils from their bodies stain draperies and furniture. 

An army cutworm moth.

“Miller moth” is a generic term that refers to several moth species that fly in large numbers and create a nuisance. Here on the High Plains the Millers are usually the army cutworm. The adults that fly in a few weeks will spend some time feeding on plant nectar, making us even crazier than we already are under this COVID-19 isolation, and then they will begin their long migration to the Rocky Mountains where they will spend the summer annoying people there. The bears won’t mind though because Miller moths are a delicious treat for them and they are known to eat up to 40,000 per day, which provides approximately 20,000 calories. (Our insectivorous bats and birds will have a good time in the next month or so as well.) 

As summer wanes the surviving moths will begin migrating back to Nebraska, Kansas, Oklahoma and the Texas Panhandle. Each female will lay as many as 1,000 eggs in the fall on wheat, alfalfa, various weeds and even turfgrass. The eggs will hatch and the resulting larvae will overwinter. Larval development in the spring is slow because it is cold, and insect metabolism is very slow when it is cold. Eventually though they will become fully grown, pupate, and next year’s moths will emerge. 

Pest News in About 10 Minutes Per Week

Extension IPM Agents on the southern High Plains and in the Concho Valley and St. Lawrence areas are now producing short audio recordings about what is being found in the field. The intent is to address current insect, weed and disease issues and look forward a bit to what might be coming next week.

For the Concho Valley and St. Lawrence areas, Brad Easterling and Haley Kennedy record and post their audio file on Tuesday afternoon. High Plains IPM Agents Kerry Siders, Blayne Reed, Dagan Teague and John Thobe record and post their audio file on Wednesday afternoon.

We will shortly start a service that will text subscribers when a new version is uploaded. For now you can go to the web page where these are posted. The photo below shows the types of topics that have been addressed in recent weeks.

Army cutworms damaging wheat

A researcher at the Lubbock Center asked us to tell her what was eating up her ryegrass plots. Suhas Vyavhare and I checked the plots and some wheat fields near Lubbock and found abundant army cutworm larvae. The growth stages are varied from small to about one-inch, so there is plenty of damage yet to come.

Nebraska has a nice 2017 army cutworm alert that states the treatment threshold is four larvae per square foot (for grain production).  Our publication Managing Insect and Mite Pests of Texas Small Grains (page 8) says, "In outbreak years, fields can have 10 - 20 cutworms per square foot." What we saw today was not to that point, but it is still early and many larvae were small and hard to find. Typical damage includes chewing on leaves, cut plants and severed stems.

The first thing you will see when scouting is the leaf damage. During the day, the cutworms will be beneath the soil surface near the plants.

Army cutworm larva.

Clipped stem on 6-inch wheat plant.

Know what you are buying in your Bt corn hybrids (including sweet corn)

The 2020 version of the Handy Bt Trait Table has just been published. This two-page quick reference guide lists the Bt and herbicide packages in all US field corn in an easy to follow manner. It also lists the pests the corn claims to control and those that have developed resistance to the trait packages. This year's changes include a discussion of finding European corn borer resistance to Cry1F corn in Canada. The table also now lists Bt toxins to which corn earworm (cotton bollworm) is resistant.

But wait, there's more! The first ever version of the Handy Bt Trait Table for Sweet Corn is now available as well. There are only a few Bt combinations available in sweet corn and the new table lists them all, including those for which resistance has been determined. Basically, only Vip3a sweet corn now provides good control of corn earworm in the south. The table lists all hybrids available in the US by company, hybrid and Bt type.

The Handy Bt Trait Tables for both field corn and sweet corn can be found here: https://www.texasinsects.org/bt-corn-trait-table.html

The following graph shows the number of corn earworm larvae per 25 ears of Bt and non-Bt sweet corn grown on the Experiment Station in Lubbock in 2019. It is easy to see that the older toxins are no longer working and in fact have many more larvae than the non-Bt types. (This is because the caterpillars are resistant to the older Bt toxins and also lose the behavioral tendency to cannibalize when on the Bts.) The graph also shows that Vip3a is doing a very good job of controlling corn earworm.