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.