Armyworms marching across the northwest Lower Peninsula

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.

Hungry hordes of armyworms are eating their way through corn and alfalfa fields in the northwest Lower Peninsula. Counties reporting problems are Benzie, Manistee, Mason, Missaukee and Osceola, but other places are likely infested. Fields with poor weed control, as well as edges of corn fields near ditch banks, fences, or neighboring pastures and legume/grass stands are most at risk.

Armyworm, Mythimna (= Pseudaletia) puncta (Lepidoptera: Noctuidae) is a grass loving caterpillar whose numbers can wildly fluctuate from one year to the next. One year it’s difficult to find any of them and then the next year they are seen in the millions marching from one field to another eating all the grass that lie in their path. Steve Gower described this year’s outbreak as “biblical” in proportion.

Armyworm closeup
A close up of an armyworm: the scourge of the
northwestern Lower Peninsula.

Armyworm feeding injury
Several rows of corn showing severe armyworm
feeding injury. All that is left of the leaves on most
of the plants is the midvein. Note that the armyworms
did not touch the ragweed, they much prefer grasses.
Photo credit: Christina DiFonzo, MSU Entomology

Armyworm riddled field
Here another shot of that armyworm riddled field
showing only the corn leaf midveins remaining.
Photo credit: Christina DiFonzo,MSU Entomology

Dr. DiFonzo’s work is funded in part by MSU‘s AgBioResearch.

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