Heading into harvest, agronomists generally haven’t seen too much unusual insect activity this year.
Soybean midge, spider mites and rootworms again emerged as some of the top pests in Midwestern fields, but insects appear to have had less of an impact this year than the year before.
“It’s been very quiet on the insect side at least until early August,” said Kelly Estes, who coordinates the University of Illinois Agricultural Pest Survey. “In Illinois, people were operating as usual and didn’t see a lot of problems from what I saw.”
There have been a few pockets of root beetles appearing in parts of Illinois and Iowa. According to Estes’ survey, there was an average of 0.05 beetles per plant so far this year across the state, but more were prevalent in the Northwestern District of Illinois.
Dry conditions seen across Iowa have been a boost for spider mites, said Iowa State Extension entomologist Erin Hodgson. These mites excel in field crops when temperatures are warm and humidity is low, she said, and can damage an already stressed crop.
“The spider mites are usually found feeding on the bottom of crop leaves,” she said. “Feeding will cause infested leaves to turn yellow and brown before they die. This can be mistaken for shooting during drought stress in maize, so farmers need to make sure they spot it.
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The midge also continued to spread from the western half of Iowa, with new confirmation of the pest in seven counties, including Polk and Warren counties. Infestation levels were still low, but there could be more problems statewide because the damage done is often mistaken for fungal pathogens, Hodgson said.
“Traditional pesticides are likely ineffective because the larvae feed inside the stem and are difficult to reach,” Hodgson said. “They like to be in soybean fields that are planted next to where another plot of soybeans was planted last year, but they like to stay on the edges of the fields.”
Japanese beetles were also a pest throughout the Midwest this year, but did not appear to be increasing at the rate of previous years. Estes said it could be due to significantly increased spray activity.
“I’ve never seen so many planes or spray platforms,” she said. “We’ve seen a lot of applications done in both corn and soybeans, more than I’ve done in any other year, and that probably reflects the low numbers we’ve seen, particularly in the eastern part of Illinois.”
Both Estes and Hodgson noted some emerging pest concerns, such as chinch bugs and stem borers. Although they are not yet widespread, they may need special attention before they get too big.
“Dectes stem borer kind of falls into this emerging category,” Hodgson said. “It is newer and we are following it. We have detected it in parts of the state, especially in the south during the summer. The northern corn rootworm is gaining more and more discussion in the northern and western parts of the state.
Every summer, a migratory pest typically enters the area, from thistle caterpillars to army worms, but so far things haven’t materialized in early September, Estes said.
“It was around this time last year when the armyworm saga started, and it’s been pretty quiet on that front,” she said. “We had a few bedbug reports, but overall it’s been pretty quiet. It’ll either be that or we’ll just wait for the shoe to drop on what’s next.