Corn rootworms staging a comeback

DECATUR, Ill. — Corn rootworms, which once headlined on agronomists’ and farmers’ lists of “most unwanted” pests, are making a comeback throughout the Midwest.

“Growers kind of got in a lull 2019 and prior. We saw corn rootworm pick up quite a bit in 2020 and it’s coming with a vengeance in 2021. We’ve seen a lot more pressure, a lot heavier pressure, in a wider span of geography,” said Travis Coffman, traits marketing manager for corn and regional crops for Bayer Crop Science.

Coffman said one factor contributing to the resurgence of the unwelcome guest in cornfields has been changing weather conditions.

“Corn rootworms do not like cold, wet soil in the winter and early spring before you get into the ground. If they’ve got those mild winters and they’ve got good soil, then they are going to continue to breed and build on the populations. The weather patterns have worked out in their favor and the populations just keep growing,” said Coffman at the Farm Progress Show in Decatur.

Coffman said the pressure has increased in both intensity and geography.

“It’s not just ‘I saw a couple of beetles,’ or ‘I saw a little root damage.’ Corn rootworm pressure is on the rise,” he said.

Scouting fields, even close to harvest, can give growers and agronomists a firsthand look at how intense pressure is in fields.

“I highly recommend growers go out and scout. It might be a little late to scout for beetles, but they can do some root digs and see what the roots look like. If you catch it early, if you know what you are going into for 2022, you can set yourself up for success,” Coffman said.

One of the primary weapons against corn rootworms is crop rotation, particularly for growers who are committed to a corn-on-corn program.

“If they are corn-on-corn for more than five years and they are seeing that really heavy pressure, then I highly recommend that they rotate their crop, go to soybeans, use some insecticides and do some different things to get those populations down,” Coffman said.

For those who don’t want to leave that corn-on-corn program, Bayer Crop Science will introduce another tool in the SmartStax lineup for 2022.

“SmartStax PRO with RNAi technology is coming in 2022. We are really excited about that trait. It is going to be the strongest biotech defense available for corn rootworm. It’s going to be a third mode of action for corn rootworm, so it’s going to be that much better against corn rootworm compared to a lot of the other traits on the marketplace that just have two,” Coffman said.

The SmartStax PRO with RNAi technology will be available in limited quantities in 2022 and has received export approvals.

“We were excited to get that approval early on in 2021, so we can get volumes out in 2022. We’ve been working this year, in 2021, so we can get it ready for 2023,” Coffman said.

Coffman said a program using a non-rootworm trait can also be effective.

“If they are struggling with the traits we have today, we recommend they go in with a VT Double PRO, which is a non-corn rootworm trait, and then use some insecticides and beetle bombs to get those populations down. Then they can come back with SmartStax technology or, hopefully, SmartStax’s PRO technology next year and it will be a really good set up,” he said.