Main insect threats to newly planted corn and soybeans

To learn more about cutworm management and risks, click here:….


In no-till fields and lush, weedy acres, slugs are also a risk for growers in high-moisture areas this spring, Seiter noted. As with cutworms, a seedling’s slow growth will greatly increase slug damage, so a shift to dry, hot weather will be a farmer’s best defense against this slimy pest.

Penn State University, located in a state that experiences high slug activity due to the high adoption of no-till agriculture, is a good source on slug management tactics. The university’s PA Slug project monitors populations and produces integrated pest management research for this difficult-to-treat pest, which – as a snail – does not respond to insecticides.

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The bean leaf beetle is a particular threat because it can cause yield loss at both ends of a season, Seiter noted. For now, the first soybeans to come will be most at risk from overwintering adults, which can feed on emerging soybean plants and cause yield loss. Later in the season, their larvae feed on the roots of soybeans and the adult beetles target the leaves and pods.

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Likewise, the colaspis grape has unique characteristics. Seiter estimates that it only reaches economic population and injury levels once every 10 to 15 years, so it can be a shocking nuisance when it does, as it did in 2018. And this pest causes the most damage to first-year corn after soybeans — a rotation that normally protects crops from certain insect threats, Seiter noted.

First, colaspis grape adults are attracted to legumes, such as alfalfa and soybeans, where they lay their eggs in midsummer. Newly hatched larvae feed on the roots of legumes during the same season, before overwintering as partially developed larvae.

The following spring, they wake up — usually in a rotating cornfield — hungry and much less picky about their food, Seiter explained. “So in Illinois we see the most problems in rotational corn, although if you have continuous soybeans, they can be very tough on the second year of soybeans in the spring as well,” he said. he declares.

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WORMS, maggots and wireworms

Last, but certainly not least, is the annual gang of soil insects that like to target young seedlings or seeds. The most common of these are white grubs – the larval stage of various beetles such as Japanese beetles and May/June bugs – corn worms and wireworms.

Grubs and wireworms tend to be at their highest levels in crop fields that have recently been converted from pasture or turf production or that regularly house cover crops, Seiter noted. Seed corn maggots prefer fields that have recently had manure applied or lots of rotting crop residue.

To learn more about white grubs and seed corn maggot, click here:… and here:….

Wireworms are particularly difficult to control or predict outbreaks, given their multigenerational habits in the soil, he added. They are also not killed by the most common seed treatment insecticides, neonicotinoids.

To learn more about wireworm challenges and a new seed treatment option from BASF, see this DTN article:….

Emily Unglesbee can be reached at [email protected]

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