Pictured: Western bean cutworm. Photo by Jocelyn Smith, Univ of Guelph
The Department of Agriculture, Trade and Consumer Protection’s weekly field report says the annual western bean cutworm moth flight continued for the third week. Counts have been very low as of July 6. Only nine of DATCP’s 41 monitoring sites reported 1-4 moths per trap.
Scouting corn plants should begin as fields enter the late-whorl and pre-tassel stages. If growers find egg masses and small larvae on 5 percent or more of the plants and control is warranted, the optimal timing for insecticide treatment is 90-95 percent tassel emergence. This application timing increases the chance of exposing caterpillars to the insecticide.
Moth counts will be available for the next six weeks on the DATCP Western Bean Cutworm monitoring network page: https://datcp.wi.gov/Pages/Programs_Services/WesternBeanCutworm.aspx
DATCP expects emergence of 25 percent of this year’s moth population during July 12-25 across the southern half of Wisconsin.
Corn Rootworm Beetle
In addition, corn rootworm beetle emergence is also starting. Beetles of the northern species were observed on July 5 in Rock County. These insects will become increasingly common this month, with peak emergence anticipated by mid-August.
According to DATCP’s 2022 corn rootworm survey, beetle counts were high across much of the southern half of Wisconsin for the second year in a row. Susceptible continuous corn fields in this region are at heightened risk of damaging larval infestations this summer. The 2022 state average count of 0.9 beetle per plant was an increase from 0.8 beetle per plant in 2021. It’s the highest average in more than a decade.
Areas most at risk of experiencing larval rootworm damage this season are the southwest, south-central, and east-central crop districts.
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