Corn Planting Decisions and Two New Publications That Can Help

There is still a lot of uncertainty about which crops to plant in parts of the southern High Plains of Texas. Cotton prices are down, sorghum faces a significant threat from sugarcane aphid, and corn requires more water than these other two crops. Many factors are involved in making planting decisions this year, and this article is strictly focused on the insect part of the equation, and the insect part is admittedly relatively minor as compared to available water, aphids and market prices.

Given that our pest pressure from caterpillars like the fall armyworm and corn earworm goes up as the season progresses, and that we have a range of Bt corn technologies with respect to their price and ability to kill these pests, there is room to save money on the front end of the season. Ed Bynum, Extension Entomologist in Amarillo, and I are suggesting that early planted corn can be non-Bt or one of the older and less expensive Bt technologies that has fewer toxins. On the southern High Plains, fall armyworm, not corn earworm, is the major threat to corn (see last year's post), and fall armyworm populations generally remain low until mid-season and then increase through the remainder of the season. Corn planted early in the planting window, and that planted in the first half of the normal planting window, stands a good chance of escaping significant fall armyworm damage. (Corn earworm is far less of a threat to corn in general because it is a tip feeder and does not puncture the sides of ears like fall armyworm.) If corn does need to be treated for fall armyworm, then we have two excellent insecticides available but they need to be applied in a window of six days centered around first pollen shed.

This being said about planting in the first half of the window, it also follows that corn planted in the second half of the normal planting window, and corn planted late, should have a very capable suite of Bt toxins if significant fall armyworm damage is to be avoided.

I should note that none of our Bt corn has any affect on spider mites, so the mite threat is the same on Bt corn as it is in non-Bt corn. Later planted corn is at less risk for significant spider mite infestations than is early and standard planted corn.

One final general statement is that there will be a lot of corn grown on the southern High Plains with reduced irrigation, and some with no irrigation. It has been demonstrated in many studies, including ours at Lubbock, that corn grown under moderate to severe drought stress is more prone to have high aflatoxin levels than corn grown with adequate water. Some people are saying that our very best Bt corn, because it has essentially no caterpillar damage, will not have aflatoxin. This is incorrect. Insects cause wounds where aflatoxin fungi can enter an ear, but even without such wounds there are many corn hybrids that can still get a lot of aflatoxin. This is a function of the genetics (susceptibility) of the hybrid as related to the amount of aflatoxin available in the system to colonize the plants at their susceptible stages. Yes, insect damage can make things worse, but no, there are no hybrids that won't get aflatoxin if the insects are controlled.

Now that I have presented the big picture I will get specific. Our newly revised "Managing Insect and Mite Pests of Texas Corn" has, for the first time, a list of recommended Bt technologies for the major caterpillar pests. These are all of the types of Bt corn that we know to be effective against a specific pest. Note that for fall armyworm the list is not as long as it would have been a few years ago; fall armyworm seems to be adapting to at least one of the older Bt toxins. To dive even deeper, the newly revised "Handy Bt Trait Table" lists the number and types of toxins in each technology. So when I say that more toxins are better, look in the Handy Bt Trait Table at the list of Bt toxins for each seed company's products. The newer and "better" (which is a relative term) Bt hybrids appear toward the end of the list of products within a seed company. Right now the very best protection against caterpillars comes from corn that contains Vip3a in combination with other toxins.

The Handy Bt Trait Table and Managing Insect and Mite Pests of Texas Corn are meant to be used together. We are indebted to Dr. Chris DiFonzo at Michigan State University for allowing us to create a southern version of her very popular Handy Bt Trait Table for the corn belt. Our version is for the cotton growing regions that have larger mandated refuge requirements than in the corn belt. All we did was take Dr. DiFonzo's publication and change the refuge requirement column. Her original version for the corn belt and counties at the top of the Texas Panhandle is here: http://msuent.com/assets/pdf/28BtTraitTable2016.pdf .

Time to prepare for Zika virus mosquitoes

You can't listen to the national news without hearing stories of Zika virus, and it is proper that people exercise caution this summer. Last year's hordes of mosquitoes are still fresh in the minds of those of us who work in the field, and if the rains come again this year we will be in a similar situation. But even a few mosquitoes can be a bad thing when they have the potential to carry a serious virus.

Mosquitoes on the front of a truck that left Plainview clean and arrived in Lubbock like this, spring, 2015.

The Wall Street Journal recently ran a story about US-based insect repellent manufacturers adding shifts and running factories around the clock in expectation of exceedingly high demand in the southern USA this summer. This was a week before the news broke in an article in the New England Journal of Medicine that said the geographical ranges of two known mosquito vectors of Zika, Aedes albopictus and Aedes aegypti, may be much broader than originally thought. A. aegypti may range as far north as Illinois and eastward as far as New York City. The article also said that A. albopictus ranges across the Southwest through parts of the Midwest as far north at Minneapolis, Minnesota and through most of the eastern United States including New England. The potential distribution maps from CDC are here: http://www.cdc.gov/zika/vector/index.html .

So what should we due this summer in addition to buying our mosquito repellent early? Drs. Sonja Swiger and Mike Merchant, Texas A&M University AgriLife Extension Entomologists, have just published a two page guide called Zika Virus: What Texans Need to Know. The publication came out today and is available in English and Spanish.  All of our Zika virus and mosquito control information is at a centralized location here. 

The New England Journal of Medicine just published a review article on Zika (March 30th).

Balancing Preventive Insect Pest Control Measures in Cotton while Bracing for a Tough Economic Year on the Texas High Plains

Suhas Vyavhare and Blayne Reed

Texas A&M AgriLife Extension

With the growing season just around the corner, farmers are busy preparing fields and making tough decisions for 2016. Cotton, the crop often known as “white gold,” looks to have some difficulty bringing major economic incentives to the farmers this year. Commodity prices have been below production costs for the last couple of years and future market moves, or lack thereof, are suggesting prices will be about the same this year. This means 2016 is going to be another challenging economic year for cotton growers. Despite this, surveys indicate increased cotton acreage in Texas in 2016. The increase in projected cotton acreage is largely the result of similar and weaker market prices of most of the usual alternative crops to cotton (corn, sorghum, wheat).  The looming threat of sugarcane aphid is also likely to prompt some sorghum producers to opt out of sorghum production.  There are some improved expectations for weather and water conditions that will be more favorable for cotton production as we come into planting season but often in uncertain times we just return to what we are best at.

With the current market conditions, one common way to balance a crop production budget is to trim production cost.  This is where we think producers are going to be faced with some hard decisions. From the insect pest management viewpoint, a big chunk of money is spent in the form of tech fees well before the crop comes out of the soil. Decisions about whether or not to plant varieties with Bt traits and whether or not to have preventive seed treatment are tough to make.

Bt cotton is genetically altered to naturally control the bollworm and other caterpillar pests as the insect feeds on the plant. The presence of Bt does not enhance yield but it can be a hedge of protection from potential yield robbing insect damage. While, in case of seed treatments, the seeds are treated with pesticides prior to planting as a preventive measure against early-season pests such as wireworms and thrips. 

Deciding whether or not to use Bt seeds and/or seed treatments is a bit like gambling. Some years the gamble works, then in the next it may not. In the past few years we did not get high caterpillar pressure in cotton on the Texas High Plains so many may feel that non-Bt cotton may do just fine.  Many of those Lepidopteran pests in recent years have been lured away from cotton toward late planted corn or sorghum and those are crops that might not have very many acres in the region this year.  It could also turn out to be a higher than average year for caterpillar pressure. In either case a Bt trait could be just the hedge of protection that protects a field’s economic margin.

Preventive seed treatments play an immensely important role in protecting seedling cotton from early season insect pests such as thrips and wireworms insuring a healthy start. Without a quick and healthy start, High Plains cotton does not tend to do very well.  If you are opting not to have an insecticidal seed treatment with decent residual properties, you will need to take extra care in early season field scouting and be ready at a moment’s notice to treat for any potential problems to save the crop and income. Remember, with early season thrips control we need to be scouting for the pest and not reacting to the damage.  If too much thrips damage has occurred, chemical treatment might pay some returns but a huge loss in plant developmental time and likely yield has already occurred and the treatment could actually hold more of a revenge factor than practical. Many producers will schedule thrips treatments around over-the-top residual herbicide applications and feel they might be achieving optimum control.  However, the timing of these applications do not always match and producers often need to make multiple thrips treatments in heavy population situations and not just one all covering trip across the field.  Also, with the foliar insecticide applications, we are likely delaying the early establishment of beneficials into our fields and possibly opening a door for other secondary pests to establish in our fields before the predators can lend their much needed hand.  Meanwhile, insecticidal seed treatments go a long way in mitigating that early and rapidly occurring damage.  

When we discuss and think through the pros and cons, using (and yes purchasing) these preventive tactics for insect pest management might just be the wiser decision. The upfront investment in preventive tools helps give us the helping hand and peace of mind that we need that might have just helped divert from a very costly disaster.  If those potential pest disasters do arise, it is very likely that those who put these measures in place should get paid significant dividend. When farmers opt for herbicide tolerant traits, addition of Bt trait should not add that much additional cost. The additional tech fee for Bt and proven insecticidal seed treatments will likely be less than multiple early foliar applications may cost in the event of a heavy caterpillar infestation later in the season.

Insect pressure will vary with general location, between fields, and will be dependent upon weather and cropping practices. Ultimately, it is important that farmers make decisions based on local agronomic and environmental conditions and should be based on solid field scouting and experience.

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.