Rootworm 'breaking through' in northern Iowa, US

Corn rootworm appears to be breaking through the multiple lines of defense set up in northern Iowa, US.

The director of agronomy for Ames-based Farmers Cooperative Company, Todd Claussen, says they knew rootworm could be a challenge this year after the intense rootworm pressure observed in 2012.

“We’ve taken multiple avenues of control—we’re using multiple traits below-ground and soil-applied insecticides,” Claussen says, “and even with those measures, with all the pressures that we’ve seen that have been created by the 2012 intense pressure, it’s starting to break through—and we certainly find 1st and 2nd instar feeding larvae on corn roots that even have multiple modes of protection.”

Claussen says they have now turned their attention to controlling the corn rootworm adults.

“Soon, in 15 to 17 days, we will see those larvae that are feeding today, we’ll see them pupate and emerge out of the ground as corn rootworm beetle, or the adult stage,” Claussen says, “and we’ll address the adult and we’ll control the adults before they’re able to lay eggs for the following year—to at least continue to manage, and keep an eye on, and avert more of those problems in subsequent years.”

Claussen says rootworm pressure in 2012 was “historic”, reaching 40 to 50 times the economic threshold level on some farms in northern Iowa.   He says that carryover pressure, combined with the reduced effectiveness of soil insecticides due to heavy rains this spring, helps explain the increased rootworm feeding activity in 2013.