Corn rootworm (CRW) is an annual problem in fields across the Corn Belt, and 2024 is shaping up to be no exception.
This year corn rootworm – along with other insects – appears to be showing up earlier than usual, says Ashley Dean, Extension specialist for field crop entomology at Iowa State University.
She believes the high numbers projected are because the pest was able to overwinter there better, thanks to the milder than usual temperatures.
CRW is the No. 1 pest of corn in Iowa, based on bushels lost and sheer geography of infestation.
“With larvae feeding on the roots alone, that can cause up to 50% yield loss,” Dean told AgriTalk Host Chip Flory on Thursday. “Sometimes those plants lodge and fall to the ground, and then they’re very hard to pick up at harvest so that can exacerbate those losses.”
In Iowa, Dean says nearly every field of corn is at some level of risk to the pest.
“Not everyone will have a high infestation but especially in continuous corn fields, which we have quite a few of, farmers can have problems from corn rootworm that are year in and year out,” she says.
Other States With Moderate Risks
A report issued on insectforecast.com on Thursday said initial, scattered corn rootworm hatch risks are now in the forecast – mainly from southeastern Kansas east into Missouri, central/southern Illinois, central Indiana and western/central Ohio.
“Heat unit thresholds have either been met or exceeded in these areas and generally, soil conditions are favorable at least on a scattered basis for hatches to occur,” says the online report.
“Growers should be aware that hatches are likely to be scattered in nature at least initially especially given recent heavy rainfall in many portions of the risk area. Scouting efforts should commence soon, if not already, in and near the risk area,” the report advises.
Insectforecast.com, founded by Mike Sandstrom, has been monitoring insect migration data and weather patterns across the country’s major crop production regions since 2006.
Beetle Counts In 12 States
Corn rootworm beetle counts that were done in 904 fields across 12 states and Ontario, Canada, last year by Bayer CropScience indicate the risks from heavy CRW populations have expanded in some areas, including in northern Illinois, Wisconsin and Ontario.
A summary of findings from the Bayer study, available here, show that:
-53% of the corn fields sampled had counts exceeding the economic threshold of 2 beetles/trap/day.
-71% of the continuous corn fields sampled were above the economic threshold, which was down from 74% in 2022 and up from 52% in 2021.
-14% of the first-year corn fields were above the economic threshold.
Tracking CRW Populations
The 2024 growing season marks the fifth year that Iowa – as part of a regional, coordinated approach – is tracking corn rootworm populations.
There are a couple of goals for the coordinated effort, Dean notes. The first is to get people out in the field to scout and place sticky traps to catch corn rootworm adults.
Dean says she has 50 such traps that are available to Iowa farmers for free for that purpose.
“We want to get traps in their hands, so that they can go out and help assess those populations in the field,” she says. (See her photo, left, of a trap that has caught CRW adults in the field.)
A second goal for the tracking project is to monitor corn rootworm for any changes to their location or populations.
“All of the Extension and industry folks that are involved with our regional network are really interested in seeing how populations are changing over time,” Dean says.
Learn more about the Corn Rootworm Adult Monitoring Network here.
Iowa farmers interested in getting sticky traps can contact her at adean@iastate.edu
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