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Japanese beetles headline potential problem pests in 2021

Japanese beetles headline potential problem pests in 2021

Japanese beetle

Japanese beetle numbers could be on the rise again in 2021.

After a few years of smaller numbers, a familiar pest might be present in Midwest fields as the summer growing season ramps up.

“In particular, I would really expect that Japanese beetles will return to higher levels of population,” said Kevin Rice, University of Missouri Extension entomologist.

Rice said in 2017 and 2018, the average for his Japanese beetle traps was nearly 2,500 beetles per week. After a drought in 2018, the numbers plummeted to 200 per week in 2019 and have started to slowly rise, recording nearly 500 per week in 2020. That pattern is expected to continue.

“If I had to guess, I would say we will be back to those 2017-18 numbers of Japanese beetles across (Missouri) this year,” Rice said.

Early calls about pests in 2021 have been about soybean maggot, University of Illinois entomologist Nick Seiter said. He said there was a lot of activity in the middle of April as cool weather stuck around after much of the planting was completed.

“When it’s cool, those soybeans take a long time to germinate and emerge,” Seiter said. “It gives an opportunity for that insect to work on those germinating seeds and reduce soybean stand.”

As the weather has warmed up, that issue is largely in the past, he said, but now black cutworm larvae are going to be large enough to cut plants and reduce stand.

“This would really be the time to scout fields and look for stand loss from black cutworm,” Seiter said. “If you see 3 to 5% of plants cut, that’s enough to trigger an insecticide application.”

Seiter said soybean gall midge is also a major issue to scout for in 2021, particularly in western Iowa. He said while it hasn’t been too prevalent in Illinois, Extension specialists are starting to teach how to scout for it in the state, as they are worried about increased spread.

Rains have delayed planting in some areas, accounting for fewer insect reports so far this year in Missouri, Rice said. True armyworm and fungus issues have been noted so far, but after planting delays the main concern comes later in the season.

Stinkbugs are a common issue for soybean and corn farmers later in the season, including the brown marmorated stink bug, which will require attention, Rice said.

“It’s been in the state for a couple of years, but we noticed last year that this pest has an unusual behavior where it likes to overwinter in human-made structures, including homes,” he said. “What was very noticeable to me last year was homeowners were calling about this bug. That tells me the population has increased and it will be a larger pest in soybeans and corn.”

Both Seiter and Rice identified corn rootworm as another issue that will affect farmers this year. Seiter said monitoring resistance to the pest is going to be key in long-term limitation.

“Resistance to those BT traits is probably the No. 1 concern we have in corn insect management in the Midwest right now,” he said. “It’s not present everywhere, but where it’s present, it’s a very serious problem.”

Seiter said the increased crop prices will make it easier for many farmers to pull the trigger on control applications this year, as it could pay off in the long run. But he encouraged being mindful of how much insecticide is being applied.

“We don’t want to cause ourselves additional damage by removing natural enemies,” Seiter said. “We would like to see it more driven by populations in the field, but there are economic thresholds that it should be based off as well.”

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