Western bean cutworm distribution maps available
Editor’s note: This article is from the archives of the MSU Crop Advisory Team Alerts. Check the label of any pesticide referenced to ensure your use is included.
Trap captures for 2007 are now posted on the western bean cutworm monitoring site at http://www.ent.iastate.edu/trap/westernbeancutworm/. There is a map of trap locations by county, plus several maps showing cumulative captures over time.
This season moths were trapped in six counties in Southern and Central Michigan: Cass, Van Buren, Allegan, Ingham, Lenawee and Monroe. The hot spot was Cass County with a total of 39 moths captured. In comparison, only two western bean cutworm moths were trapped last season, again both in Cass County. This insect appears to have moved further north and east in the Michigan.
Why the concern? Western bean cutworm has moved rapidly cross the Midwest from west to east. The major feeding sight for western bean cutworm larvae in August is in the ears. In some western states, larvae cause severe damage late in the season. Spray applications are made, or growers must choose among different Bt hybrids. Moth numbers are still low in Michigan, and we have NOT documented feeding in ears by western bean cutworm larvae. But in scouting corn in mid- to late-August, be alert for what appears to be “giant corn borers” in ears – this may be western bean cutworm, but there are several caterpillars that feed on ears, such as European corn borer, earworm and armyworm. Collect specimens if possible and preserve them in alcohol – commercial grade ethanol, vodka, tequila, etc. Rubbing alcohol can be used in a pinch, but it isn’t as good of a preservative. Bring the specimens to your county extension office so they can forward them to Howard Russell or me, Chris Difonzo, at the MSU Diagnostic Services.
For the future, here are several free western bean cutworm references on-line:
- Picture of a WBC larva: http://www.ent.iastate.edu/imagegal/lepidoptera/wbcutworm/40wbcutworm.html
- “Don’t confuse western bean cutworm with other moths.” Shows pictures of common moths that can be confused with western bean cutworm. http://www.ent.iastate.edu/trap/westernbeancutworm/files/wbc_id.pdf
- “Identification of western bean cutworm and similar species.” This slide set shows distinguishing characters of larvae attacking corn http://ipcm.wisc.edu/Portals/0/Blog/Files/19/236/3_Look_alikes.pdf