A hidden monster lurks under the ground, destroying the corn crops and the farmers’ profits.
Midwest flooding may have reduced populations significantly in 2015, but expansive testing and farmer surveys show corn rootworm is on the rise.
“We’ve started to see an increase in population, especially in the last two years in certain geographies, based on survey data that we’ve done internally as a company,” says Preston Schrader, Bayer seed and trait technology development representative. Crop Science. .
The lack of significant weather events and a growing number of farmers committed to corn-over-corn acres may have led to population growth.
“As the economy changes, we’ve had more demand for corn over corn,” says Bruce Battles, manager of technical agronomy at Syngenta. “We see more growers committing to at least two to three years of corn farming before going back to soybeans. As you do that, you start building populations.”
Relying heavily on seemingly simple solutions can also play a role in the growth of the infestation.
“It’s human nature to want a simple solution,” says Battles. “It’s no different than what we’ve seen in other areas of agriculture, like weed control. He finds a new tool, it is adopted on a large scale, and then he begins to see resistant weeds. In some pockets, we are seeing similar things due to a heavy reliance on a singular approach like pyramid traits. [several traits stacked on each other]. Over time, that catches up with you, and I think we’re dealing with the result of some of those years of simplicity.”
Continuous data collection in the fields is a farmer’s main defense against corn rootworm.
“From a central rootworm pressure standpoint, knowing and understanding the problem at hand is key,” says Travis Coffman, Bayer Crop Science trait marketing manager for corn and regional crops. “So there are many solutions or practices that you can implement.”
With no rescue treatments available, growers must diligently plan for rootworm pressure before the growing season begins.
The eggs that rootworms lay in the summer and fall usually don’t hatch until the following year. “Unfortunately, those eggs are underground, so there are very few inexpensive options to control those bugs as soon as they hatch,” says Schrader. “That’s why, from a protection standpoint, you really have to think before you throw the seed in the ground about how it’s going to protect against rootworm.”
Data from previous growing seasons can help growers determine their risk of rootworm damage.
“Look at the current year and make decisions from that,” says Battles. “I highly recommend people build a plan for 2023. Learn as much as you can in this year to build that plan for 2023 because the best way to learn is to get out in the field.”
Routine root digging can help quantify the amount of damage a grower faces.
“That’s the first way to identify if you have pressure there,” says Coffman. “If you have pressure, those roots would rate on something like the 0 to 3 scale from the state of Iowa. [0 is no damage, 3 is severe]. That’s a way to economically identify the potential damage it will have from a performance perspective.”
Farmers can also place sticky traps in fields to understand population pressure and make better management decisions.
“Traps are a very good indicator of which fields will be most at risk in 2023,” says Battles. Fields that are particularly high risk could benefit from a beetle spray program, a practice that can reduce eggs but also requires timely application.
Whenever possible, rotating with soybeans is one of the most effective ways to control corn rootworm.
“Soybeans are a non-host crop, which means the rootworm cannot survive on soybeans,” says Schrader. “When you rotate soybeans, the beetles don’t have the ability to hatch the next year because they depend on the roots of the corn to live. That’s why a corn rotation works so well.”
Some rotation-resistant corn rootworms have been detected, but the risk to corn-on-corn production remains much higher.
“The situations where you find corn upon corn are the ones where you really need to consider what traits you’re using for your farming program because you want to make sure you’re adequately controlling those major rootworms,” says Schrader.
Working with local agronomists and other experts, in addition to using pyramid products, can help farmers create a plan.
Bayer recently introduced SmartStax PRO with RNAi technology, offering farmers a new tool to deal with corn rootworm pressure.
“This pest has a high probability and a great ability to adapt to whatever technology we develop,” says Schrader. “We are always trying to develop new modes of action to control this pest and stay one step ahead.”
While previous products have focused on multiple BT proteins, RNAi technology can identify specific proteins that corn rootworms need to survive.
“We have limited volumes in 2022 that we’re talking to farmers about now, and in 2023, we plan to expand that quite a bit,” says Coffman. “Last year in particular, we found that it will be the strongest biotech defense against corn rootworm compared to all other competitors on the market.”
With three modes of action in one product, SmartStax PRO with RNAi technology offers the opportunity to extend the life of existing management options. It’s an exciting development, but Battles warns farmers to remain cautious.
“If we go into this with the mindset that RNAi is what’s going to take care of rootworms, and it becomes our only management strategy, resistance is just a matter of time,” says Battles. “It’s a question of how many years it takes for that new technology to become obsolete. There are a lot of good technologies coming out, but I encourage people not to see that as the singular new approach to handling the problem. It does not replace the need for a multifaceted approach to management.”