Overall, rootworm pressure has been relatively low the past few years. But Sean Evans, technology development manager with Monsanto, doesn’t want that fact to keep farmers from being vigilant about this major corn pest.
“We want to be careful that we’re making decisions with the proper preparation,” he says.
Don’t go trait-free in corn-on-corn acres, for example, Evans recommends. Invest in trait packages that offer multiple modes of action (e.g. SmartStax RIB Complete) for fields that could show the greatest risk, he says. And know a field’s history and take copious amounts of notes throughout the season on what pests are present – chances are if rootworms were heavy in a field last year, they’ll make an encore appearance this year, he says.
“Your best indicator is what happened in your fields the year before,” he says. “That’s one reason why we encourage late-season insect scouting.”
This winter’s relatively mild weather is also a factor to watch, Evans says.
“Overwinter survival has been really good,” he says. “If we have an early spring with relatively dry conditions, hatch could occur earlier and be quite significant. It takes below-freezing temperatures for 20 to 30 continuous days, and we haven’t even frozen the top 3” to 4” of soil for any significant amount of time here in central Illinois.”
In contrast would take an exceptionally cold winter with little to no snow cover to create significant winterkill, Evans says.
Farmers who are swapping out acres to non-traited corn should think about more than just rootworms, Evans adds. In particular, keep a watchful eye on corn borers on these acres, he says.
“The Bt traits are so effective, it’s easy to lose sight of them,” Evans says. “But it doesn’t take much of a corn borer infestation on non-traited corn to take 20% of your yield pretty quickly.”
Evans suggests two free resources from Monsanto – insectforecast.com and the Apple app Corn Rootworm Manager – to monitor in-season rootworm risks and assess field-by-field recommendations.