Cooler Weather Conditions, Late Planting, Impacts Insects on Crops

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Source: Ohio State University

COLUMBUS, Ohio -- Rainy, cooler weather experienced recently throughout the region means slugs may be on the rise in some field crops, says an entomologist with the College of Food, Agricultural, and Environmental Sciences at The Ohio State University.

The rains combined with colder temperatures are ideal slug weather, said Kelley Tilmon, a field crop entomologist with Ohio State University Extension and the Ohio Agricultural Research and Development Center. OSU Extension and OARDC are the outreach and research arms of the college, respectively.

Because slugs love these cooler, wetter conditions, Tilmon said growers need to be on the lookout in their corn and soybean fields for slug feeding damage, which can sometimes be heavy. 

“During crop emergence, farmers should scout their fields for slugs, especially in fields with a history of slug damage,” Tilmon said. “As plants emerge, these young slugs will be hungry and feed on corn and soybean, with no-till fields with high residue at a higher risk.

“Wheat fields at this point are less likely to experience economic feeding damage from slugs – the wheat is much further along and the larger plants are less susceptible than little seedlings.”

The adverse conditions that are making fields appealing to slugs will, however, have varying impacts other cops from other insect pests, she said.

Spring planting across the region continued to be slowed heavily by cold, wet conditions, Cheryl Turner, Ohio State statistician of the U.S. Department of Agriculture’s National Agricultural Statistics Service, said in a written statement.

“As of the week ended May 15, corn and soybean planting progress is behind both last year and the five-year average, as farmers have been unable to get into fields that are soggy and, in some cases, in standing water,” she said in the statement. “Some areas saw cool enough temperatures to have frost on Sunday morning.”

As a result of late planting, growers are going to see some shifts in the phenology of their crops this year, meaning the plants will be younger later in the growing season, Tilmon said.

“That can affect the insect pests – crops could be either more or less vulnerable to insect attack depending on the insect,” she said. “Soybean fields that are already up will be at higher risk for first-generation bean leaf beetle feeding as they look for those first fields, but later-planted beans may escape. 

“On the other hand, late-planted beans may be at greater risk from second-generation beetles in late summer because they will be greener and fresher.”

Already, there have been reports of high numbers of black cutworm in traps across the Midwest, which suggests that the pests may be in some fields, Tilmon said. Developing larvae feed on emerging corn, meaning growers need to look out for corn with leaf feeding or stem cutting as the crop emerges, she said.

“While traps are indicating higher than average black cutworms, that doesn’t always mean that they will be out in fields in higher numbers,” Tilmon said. “Producers should, however, be on the lookout.

“Whether or not growers find black cutworms in their fields really depends on the location and conditions of their fields. Growers in southern Ohio may see some feeding this week.”

Wheat growers need to be on the lookout for armyworms and cereal leaf beetles, although indications are that this season may not be a breakout year for armyworms, Tilmon said.

“Armyworms can be hard to predict, but based on data obtained from the University of Kentucky armyworm trapping program, Ohio growers may not have a big problem from the pests this year,” she said. “But wheat growers should still scout for armyworms, which look like striped caterpillars, in their fields.

“Growers who are planting corn into rye cover crops should also be on the lookout.”

Adult cereal leaf beetles have also been reported, so growers can soon expect larvae to begin feeding, Tilmon said, noting the small black larvae can resemble bird droppings.

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