Although some of the new insect control trait technologies coming through the developmental pipeline from Bayer CropScience for 2020 may not have a direct application to your row crop operation, there are some that do. According to Dr. Scott Stewart, Extension entomologist, University of Tennessee, growers should review information on what is becoming commercially available and cross-reference that information against available Extension data to help make a more informed decision.
Stewart and Matt Rhine, technology development representative, Bayer CropScience, broke down the new cotton, corn, and soybean trait offerings at the Union City AgKnowledge Field Day and over 300 farmers were in attendance to listen. “This Trecepta variety is bringing three different Bt traits to the market,” says Stewart. “The VIP trait found in Trecepta brings greatly improved control of corn earworms.”
Most cotton producers in the Mid-South have seen Bollgard II becoming less effective on bollworms. “Bollgard III will help combat that, as it also contains the VIP trait, and Bollgard III varieties give you that flexibility of going over the top with glyphosate, dicamba, and glufosinate (Liberty),” says Stewart.
Depending on the registration and export approvals, there may be a cotton lygus trait variety coming for 2021. “When this new technology was first being developed, Monsanto called it a ‘lygus’ trait, which is actually the genus name for tarnished plant bug,” says Stewart. “It wasn’t long before testing showed that it provided much-needed control of thrips, and thrips are the top insect pest of seedling cotton.”
In a cotton insecticide trial that Stewart did this year, he used every available insecticide option to affect control, but crop injury was still substantial. “I believe this is where this lygus trait technology will shine, because much less thrips injury was observed in test plots having this new technology,” says Stewart.
Work conducted by Stewart’s previous graduate student confirmed that Bt lygus trait provides some control of tarnished plant bugs. “They don’t lay as many eggs, and it also has a negative effect on their growth,” says Stewart. “It’s not a stand-alone control for plant bugs like it appears to be on thrips, but it definitely reduces the numbers. You won’t have to make as many insecticide applications if you use the new lygus trait, and that’s where you’ll potentially save some money.”
Stewart has seen significant yield losses if threshold numbers of plant bugs are reached and insecticide applications are not made — and this includes cotton having this new lygus trait. “In reality, you’d still have to make some sprays anyway because this technology doesn’t control stink bugs — especially if you’re not spraying as much for tarnished plant bugs,” says Stewart. “Stink bugs will slip in on you. This isn’t a walk-away technology.”
Stewart expressed concern about the VIP technology being placed in corn varieties, like the Trecepta technology. “Other entomologists around the Mid-South and I are worried about selecting resistance in corn that will impact corn earworm (a.k.a. bollworm) control in cotton,” says Stewart. “We are dependent on VIP trait also present in Bollgard III, TwinLink Plus, and Wide Strike III to get us over the hump until the next trait is released because we’re seeing bollworm resistance to the Bt traits present in Bollgard II, TwinLink, and the original Wide Strike technology, and quite frankly, we’re seeing little economic benefit, at least in our geography, of having that VIP trait in corn. The increased protection against corn earworm in corn having the CIP trait is really not translating into yield.”
Resistance, remaining vigilant on soybeans
Some corn farmers in Texas have observed corn earworm infestations where the VIP technology is being used in corn. “We’ve not seen much of this in the Mid-South, but that shows the potential for resistance is out there and is real,” says Stewart.
The Mid-South corn, cotton, and soybeans crops are progressing, and according to Stewart, progressing well. “I always like to remind farmers to be vigilant in soybean scouting the remainder of the growing season as we near corn and cotton harvest,” says Stewart. “From this point forward, you’ll have 90 percent of your insect problems in soybeans. Stink bugs will start spiking when you hit R5/R6, which is also where your late-season caterpillars increase.”
Soybean pest pressure has been relatively low this year, but Stewart reminds everyone that when corn is drying down and cotton is finishing up, all of those pests will be looking for something green on which to feed. “Their most readily available choice is late-season soybeans,” concludes Stewart.