Planting Time and "Compliance" with Bt Corn Refuge Rules

Bt transgenic corn with insect protection can be planted as an integrated seed blend in the Corn Belt, but has mandated block or strip non-Bt refuge requirements in the southern USA where cotton is grown. Depending on the type of Bt corn, the required refuge is from 20 - 50% of planted acres. This means that 20 - 50% of the crop is subject to damage and yield loss by the pests intended to be controlled by the Bt toxins, and it also means that growers must clean out and reset their planters to deliver non-Bt seed after planting the primary Bt crop. This takes time, and time is at a premium during planting season.

When Bt corn is up for registration with EPA, the seed companies present an Insect Resistance Management (IRM) plan designed to slow down the development of resistance. Upon registration of the Bt technology, EPA mandates that the seed companies enforce the plan and provide annual evaluations of "compliance" by growers. When transgenic corn seed is sold, the companies make corn growers sign a document that says they will abide by the IRM plan. (This document is known as the Stewardship Agreement.) If growers request it, there is plenty of literature and individual help to know how to plant the refuge so as to be in compliance with the Stewardship Agreement. After planting, the seed companies have the authority to inspect on-farm acres that are planted to their technology. Growers must demonstrate that they are following the IRM plan, and if found "out of compliance" are subject to further inspection in the next growing season. There are no other penalties to growers for non-compliance, at least until year three, when an individual seed company can (and certainly will) deny the non-compliant grower access to their technology. The grower then can purchase Bt seed from another company.

This article is not about the rules of refuge planting, it is about what is ultimately compliance with the diktats of a Federal agency. I have friends in EPA who work in the division that negotiates IRM plans with transgenic seed companies. These people are excellent scientists and go to great lengths to develop a plan that will extend the life of the Bt toxins before insects become resistant. (It is a given that insects will become resistant, and the IRM plans seek only to delay that resistance.) Seed companies also want to delay resistance to their Bt toxins, in part because, in spite of conventional wisdom, they don't have new toxins waiting in the wings to clean up a resistance problem when it develops. The IRM plans in the Stewardship Agreements are the best estimates based on science as to how to delay the arrival of resistant insects that will make the technology ineffective.

However, in spite of what happens in Washington DC and corporate offices, the real power in determining how long Bt corn technology lasts is held by the men and women who plant corn seeds. You can follow the IRM plan and extend the life of the technology, or you can refuse to plant the refuge and shorten the life of the technology. The idea of "compliance" with what EPA wants is at best irritating, and some people would choose to not plant a refuge simply because EPA deems that it should be done. In one respect compliance might seem like bowing to the wishes of Washington DC and the seed companies, but in reality it is about the future. The best reason to plant a refuge is to extend the life of the technology. The choice is yours, and in the end that is the way it should be; you and your neighbors have the power to decide how long the technology lasts.

Bt Corn and Resistance Clouds

Cracks small and large are beginning to appear in our Bt (transgenic) corn targeted at controlling insects. To date we have confirmed resistance in corn rootworm to Cry3Bb1 and mCry3a. In the caterpillars we have confirmed resistance to Cry1F in fall armyworm, and likely resistance to Cry1F in southwestern corn borer and western bean cutworm. There was recently a population of cotton bollworm (corn earworm) with elevated levels of tolerance to Cry1Ac reported in Arkansas, and bollworm seems to have been becoming less susceptible to Cry1Ac in the cotton belt for many years.

None of this should be a surprise because transgenic toxins are really no different from traditional insecticides; the more you use them the faster the insects become resistant. What is different is that traditional insecticides last only a few days or weeks and are gone; our transgenic crops express toxins all season and can select every generation of a pest for resistance. And also unlike traditional insecticides, we are planting almost all of the U.S. acres to insect resistant transgenic corn and cotton. In corn around 90% of the acres contain Bt toxins for insect control (whether that protection is needed or not). Amazingly enough, two seed companies are considering introducing insect resistant transgenic soybeans in the mid-south, where we already grow transgenic corn and cotton with the same toxins as planned for soybeans.

Transgenic corn for caterpillar control was introduced in 1996, and at that time we tried to build Insect Resistance Management (IRM) plans to prevent resistance from developing for at least 20 years. That effort was mostly successful, with the exception of fall armyworm and Cry1F; the confirmed failure was documented 2010. Since 1996 the seed companies have put additional toxins in corn and cotton and created pyramids of Bt toxins. A pyramid is when there are two or more toxins targeted at the same pest or pest group. For example, Pioneer Leptra is Cry1Ab + Cry1F + Vip3a, and all of these are targeted at caterpillars. These are the same caterpillar toxins as in Syngenta's Agrisure Viptera 3220 and Agrisure Duracade 5222. A stacked pyramid has pyramids for two different types of pest, and Monsanto's SmartStax is a good example. It has Cry3Bb1 + Cry34/54 targeted at corn rootworm, and Cry1F + Cry1A.105 + Cry2Ab2 targeted at caterpillars. Transgenic seed companies are now cross-licensing their toxins, and this effectively means that insects can be exposed to the same or similar toxins regardless of the company that supplied the seed. More and more acres are being planted with the same toxins regardless of the company from which the seed was purchased.

The idea of a pyramid is that it delays resistance by having multiple toxins present. If an insect is resistant to, say, Cry1F, it will likely be killed by another toxin in the pyramid. But now our pests are beginning to develop resistance to several toxins, and it might be that only one toxin in a pyramid of three toxins still has full efficacy. This would mean that the resistant insects are actually being killed by only one of the three toxins, and at the same time are being selected for resistance to that toxin. Vip3a is the latest toxin to be introduced to pyramids for caterpillar control and it works very well, at least for now. But the most modern Bt corn hybrids from DuPont Pioneer and Syngenta already have Vip3a, and Monsanto's next generation of Bt corn will have Vip3a as well. (And it is now in some types of Bt cotton.)

I have written all of this to say that insects are now showing early signs that our Bt technologies are not the panacea that we once hoped they were. Resistance is a natural result of the use and over-use of a technology, and we should not be surprised in the coming months and years to hear that resistance has been confirmed to this or that Bt toxin. The important thing will be to let someone know if you see unexpected insect injury in your crops. We can make collections of insects and send them for resistance screening. It is vital to know where the pockets of resistance are and how far they have spread. In fact, depending how early the resistance was detected and on the pest and extent of spread of resistance alleles, it may be possible to wipe out a local resistance episode. So don't hesitate to pick up the phone and call your local Extension Entomologist or IPM Agent, crop consultant or seed company representative if you see unusual damage in your Bt crops.

FOCUS on Entomology: Extension Cotton Entomologist Begins Work in Lubbo...

FOCUS on Entomology: Extension Cotton Entomologist Begins Work in Lubbo...: We are pleased to announce the arrival of Dr. Suhas Vyavhare, the new Extension Entomologist for cotton on the High Plains.  He has written ...

Extension Cotton Entomologist Begins Work in Lubbock

We are pleased to announce the arrival of Dr. Suhas Vyavhare, the new Extension Entomologist for cotton on the High Plains.  He has written about his background and cotton entomology focus below, and his contact information is here: E-mail: Suhas.Vyavhare@ag.tamu.edu, address: 1102 E. FM 1294, Lubbock, TX 79403-6653, phone number: office (806) 746-6101 or cell (806)220-4228.

I consider myself a farmer first then a scientist/researcher. It was my early childhood on a small family farm back home in India which made me passionate about the science of agriculture. After having completed high school, it was an obvious choice for me to go to a College of Agriculture to pursue an undergraduate degree during which I became interested in entomology. It is that curiosity and the interest along with a strong desire to pursue graduate studies overseas landed me in West Texas A&M University (WTAMU) in Canyon Texas where I obtained an MS degree.  I worked on screening  sorghum genotypes for resistance to maize weevil under the guidance of Dr. Bonnie Pendleton. I completed a PhD in entomology at Texas A&M University, College Station where I was co-advised by Drs. M. O. Way and R. F. Medina. My PhD research focused on the development of an integrated pest management (IPM) program for redbanded stink bug (RBSB), an invasive insect pest of soybeans in the southern U.S. For this project, I conducted field experiments to study the impact of RBSB feeding on soybean production and the occurrence of delayed maturity disorder. My dissertation research was the first to report an occurrence of the most damaging species of stink bug, RBSB, in Texas soybeans. One of the objectives of my PhD research also involved investigation of development of insecticide resistance in RBSB field populations. 

Following my PhD, I worked as a postdoctoral researcher at the Texas A&M AgriLife Research and Extension center in Beaumont where I worked towards addressing insect pest issues in soybean, sugarcane, sorghum and rice across the Upper Gulf Coast region. Overall, I have over five years of experience in designing and conducting field research establishing economic thresholds, evaluating insecticide efficacy including promising seed treatments, and germplasm screenings for insect resistance in diverse agricultural crops.

My long-term association with the Beaumont Center as a graduate and postdoctoral researcher has further strengthened my understanding of relevant regional pest management issues. This experience has provided me with excellent opportunities to actively work with other researchers, IPM agents, county extension agents, industry cooperators, and ag-consultants to address stakeholders’ issues. I am a strong advocate of a need for an extension education in agriculture. I think it is not enough to conduct research on research farms. I strongly believe in the need to disseminate and apply research findings to solve stakeholders’ problems. As an extension specialist I am committed to ensure that new technologies and discoveries reach farmers’ fields in such a way that farmers are empowered to use them.

Agriculture has become very challenging in recent times. There are environmental extremities farmers have to face, new insect pests and diseases show up every now and then, and finally after having a commodity in hand there is an uncertainty surrounding market prices. With the fierce competition from global producers and volatile commodity prices, we need to provide our producers with the technology that will not only increase the pounds per acre but also cut down the production cost to help producers stay in business. In this position, I envision developing a well-rounded program that will involve an active participation and cooperation from cotton producers, IPM agents, extension county agents, crop consultants, and commodity groups like Plains Cotton Growers Inc. to deliver information that will directly address the issues faced by cotton producers in the Texas High Plains. Also, being a strong supporter of modern technology in agriculture, I am very eager to initiate collaborations with industry folks to evaluate and screen different tools in order to provide multiple options to clientele. Finally, I am very excited about having the opportunity to work in an area I am passionate about. I am confident my program can make significant contributions towards developing nationally recognized Extension and applied research programs to address regional entomological issues and improve economic productivity across the Texas High Plains.

Sulfoxaflor (Transform), Federal Courts and The March of Folly

Sometimes a regional decision with national implications can have dire unexpected consequences half a nation away. The Ninth Circuit Court of Appeals in California handed out a ruling in early September that EPA should withdraw the Federal registration for sulfoxaflor insecticide. The logic for the decision was that sulfoxaflor was a neonicotinoid insecticide (according to press coverage) and EPA should not have registered it without more honeybee safety studies. Indeed, EPA did ask the Registrant, Dow AgroSciences, for additional bee safety data but registered the insecticide for national use without those additional studies. (Neonicotinoids are getting some of the blame for the decline in honeybee numbers, but the science on the issue shows it is a very complicated problem and insecticides might only play a minor part. The companies that manufacture and sell neonicotioids are making enormous (and expensive) strides in limiting bee exposure when valid science says there is a real risk.)

The initial dataset submitted by Dow AgroSciences to EPA did show some sufloxaflor toxicity to bees, and that is why EPA wanted further studies. However, in spite of the fact that every press release I could find on the court decision labeled sulfoxaflor as a neonicotinoid, the truth is that it is not a neonicotinoid according to the Insecticide Resistance Action Committee (IRAC), an authority on pesticide mode of action. IRAC lists Class 4 as Nicotinic Acetylcholine Receptor (NACHR) Competitive Modulators, but the subclasses are not the same. Neonicotinoids are in Class 4A (neonicotinoids). Sulfoxaflor in Class 4C (sulfoxaflor). (http://www.irac-online.org/modes-of-action/). While sulfoxaflor and the neonicotinoids target the same site they apparently differ the way they affect the site, and that is why IRAC has them in different subclasses.

EPA, which is not known to be friendly to insecticides, explains bee safety in their  sulfoxafor registration, and note the label restrictions on using it on pollinating crops. “The EPA does not allow sulfoxaflor application to plants that are attractive to bees for three days before bloom, during bloom, or until petal fall for the majority of crops. For the remaining bee-attractive crops, we also added advisory language to the labels to notify known beekeepers of scheduled application and to apply these products in early morning or late evening. Since bees are typically only present when plants are in bloom, and the toxicity of sulfoxaflor residue is primarily a concern when the residue is freshly applied (the residue generally dissipates within three days), we expect that the application restrictions we put in place will protect bee colonies from harmful exposure.” (http://pesticides.supportportal.com/link/portal/23002/23008/Article/35618/Why-did-EPA-register-sulfoxaflor-I-heard-it-harms-bees) [Link seems to have been removed 10/16/15 or before.]

By now your eyes might be glazing over, but it was necessary to establish these facts before pointing out a looming disaster that might occur if sulfoxaflor is not returned to the market for use on sorghum in 2016. The sugarcane aphid (Melanaphis sacchari) underwent some type of genetic shift a few years ago, adapted to sorghum, and has been decimating sorghum crops in the southern U.S.A. since 2013. It is fair to say this has been a crisis for sorghum growers; typical yield losses are 60 – 100% if the aphid is not controlled. This pest has rapidly expanded its range and can now be found as far north as Colorado and Illinois. The latest distribution map is here: http://txscan.blogspot.com/2015/10/new-map-17-states-and-417-counties.html .

Presently there are only two insecticides effective against sugarcane aphid; sulfoxaflor (sold as Transform) and Flupyradifurone (sold as Sivanto). Our traditional, older aphid insecticides provide only mediocre control, and in fact they kill beneficial insects that help control sugarcane aphids and this makes the aphid outbreaks even worse than if no insecticide had been applied. (These older insecticides are also extremely toxic to honeybees.)

The Federal court system has taken away one of two effective sugarcane aphid insecticides, so most people would think that since there is one left it is no big deal. But it is a big deal, and a very scary big deal. Aphids are renowned for developing resistance to insecticides. There is very little sexual reproduction (resulting in mixing of genes) in aphids and females are born pregnant and give birth to live young that are genetically identical clones of the mother. If a female has genes for resistance to an insecticide then all of her progeny will have those genes.

Sivanto is an IRAC Class 4D insecticide (Butenolide) and different from the Class 4C Transform. The foundation of insecticide resistance management has always been that if an insecticide must be used, then any additional insecticide use in the same season should be with a product with a different mode of action.  It is likely that resistance that develops to Sivanto will not protect sugarcane aphid from Transform applications, and the reverse is true as well. But now we have only one effective insecticide for sugarcane aphid, Sivanto, and it will be used on the vast majority of sorghum acres grown in the U.S. in 2016. The very best way to get resistance to an insecticide is to use it over a large area on multiple generations of a pest, and that is precisely what we are going to do with Sivanto in 2016 if Transform (sulfoxaflor) is not restored for use on sorghum.

So thanks to a Federal Court Ruling in California we now stand a very good chance of blowing out (developing resistance to) Sivanto, the sole remaining insecticide effective against sugarcane aphid and the last insecticide that makes sorghum an economically viable crop when sugarcane aphids are present. Right now, and until we get good sources of host plant resistance and/or an improbable new insecticide, all that stands between sorghum and disaster is Sivanto. I’m sure the Federal Court in California made its decision on the narrow scope of the case before it, but it is imperative that an exemption to allow sulfoxaflor to be used on sorghum in 2016 be granted. If we don’t have that exemption and Sivanto begins to fail then we will resort to the older, less effective but more bee-toxic insecticides and people will really get an idea of what bee toxicity means.

Fall Armyworm Trap Captures Very High

As we start to wind down the season there has been a late surge of fall armyworm moths captured in the Lubbock traps. This puts late sorghum at risk of headworms. It also puts very late planted corn at risk of fall armyworm infestations in the ear.

Rumors of Sugarcane Aphid Resistance and Adaptation to Corn Are Unsubstantiated

Dr. Ed Bynum has addressed some unsubstantiated rumors flying around the High Plains; 1) that sugarcane aphid has become resistant to insecticides in Mexico and 2) that it is now able to develop on corn and is damaging corn in Mexico. I tried to address this last topic in my post last week, but Dr. Bynum has provided more detail on both issues in his newsletter post today.

The bottom line is that there is no evidence of insecticide resistance and no evidence that the aphid can damage corn.