Rootworm Pressure Expected to Rise in 2021

Increased corn rootworm pressure on corn crops suggests there will be a need for more application of corn soil insecticides in 2021.

A fall 2020 survey by AMVAC compared 2020 corn rootworm pressure to that of 2012, after which, use of soil-applied insecticides was elevated for the three seasons of 2013-2015.

Jim Lappin of AMVAC says retailers saw an increase in corn rootworm pressure in 2020, and expect the same trend in 2021.

“Our goal was to talk to our retailers about the coming season to make sure we would be able to serve the needs that they saw developing in the market coming forward. Overwhelmingly, we heard from retailers that they’re anticipating an uptick in soil insecticide demand based on a higher-than-normal corn rootworm activity, or rootworm activity more reminiscent of what we saw back in 2012-2013.”

Lappin says there are many reasons why there is more corn rootworm pressure in 2020 and heading into 2021. The ideal growing condition for corn is also ideal conditions for corn rootworm, and weed control can play a factor as well.

“Going into early June, there were a lot of growers told they may not have the ability to spray dicamba later in the season, so a lot of guys ran out and made earlier applications of dicamba and what that resulted in is that dicamba has a limited residual period. So, all of a sudden you had really clean fields in June after they sprayed, but then as the season progressed, as more rainfall occurred, now of a sudden you had some late season weeds that came through, and those created extra places for rootworm the feed.”

Lappin says the best way to combat corn rootworm is rotating crops.

“Rotating to soybeans in a field where you’ve had high pressure or suspected high pressure is one option, but that’s not always a viable option. A lot of growers, particularly in livestock heavy areas need that corn for livestock feed. So, if they’re going to continuous corn situation they need to look at their overall strategy and our recommendation is pick the hybrids that make the most sense hit your yield objectives and then design your insect strategy around those hybrids.”

He says it’s important to monitor your fields.

“Get out there scout your fields, you can use sticky traps to gauge the number of beetles you have out there. That’s not always an indicator of high pressure the following season, the typical rule of thumb is if you can find an average of one beetle per plant, even if only five percent egg survived that could mean substantial economic loss.”

Lappin of AMVAC says soil applied insecticides can help protect your corn from rootworm and protect your yield.

“We have options that would include bagged material if he has an older plan with an older insecticide hopper, we have our SmartBox system, we’re introducing our SIMPAS system, we have liquid options available that can be used. So, based on how that grower has his planner setup, does he have insecticide boxes, does he want to purchase a system like a SmartBox or a SIMPAS system to address that need, or can he use a starter fertilizer to address the need through those types of solutions.”

He adds it’s important to be proactive.

“Unfortunately, there’s no rescue operation for corn rootworm if you don’t control them early on. You can come in and use a beetle spray type of a program, it’s not going to help you with that year but it could reduce the number of beetles that are laying eggs for the subsequent year. In most cases, people are being proactive, they’re using at plant solutions, whether it’s a trait package, a soil insecticide, a liquid insecticide, their using some type of management practice to ensure they don’t have that negative impact of those insect pressures.”

Learn more about controlling corn rootworm in 2021 at or contact your local retailer.