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Agronomist predicts bumper crop of corn rootworms

An agronomist says the near perfect 2020 growing conditions were also perfect for growing pests.

Michael Weiss consults for Bayer in central and southern Wisconsin, and says, “We had a good planting date. Everything got planted timely, so when the eggs hatch in the soil, there’s plenty of corn roots there for the larvae to develop on, so I think we just had essentially a bumper crop of corn rootworms this year.”

Weiss tells Brownfield the state ag department’s annual survey of adult rootworms shows the highest beetle pressure in at least five years and the second-highest count in 16 years. “Those guys that are going continuous corn either in a grain situation or a silage situation, they might have to consider a rootworm management plan for 2021.”

Weiss says farmers in central and northern Wisconsin tend to rotate corn with soybeans or other crops, where many in southern Wisconsin will grow continuous corn, which is commonly done in Illinois.

And in the central sands where many growers raise vegetables like sweet corn for canning, the late-planted sweet corn is at risk. “Late-planted sweet corn, it has green silks, and it can attract a lot of corn rootworms, so it can be essentially like a trap crop, if you will.”

Weiss says he does not expect a major corn rootworm impact on the 2020 yield but says farmers will likely need a corn rootworm management plan next year.  He says another problem is the dry weather, which is forcing farmers to chop corn silage early before it gets too dry, making it harder to pack and less desirable for the cows.