Young Western Bean Cutworm Larvae

Some scouts are starting to notice tiny WBC  larvae that have hatched that crawling in the whorl or making their way down to the ear of the plants.  To help you know whether they are WBC larvae, here are some photos.  You can click on them to enlarge them.

They start out with spots along their bodies (spots have tiny short hairs coming out of them).  You will need a handlens to really see the spots.

Newly hatched WBC Larvae (T. Baute, OMAFRA)
Closeup of newly hatched WBC larvae (Photo Credit: Chris DiFonzo, MSU)


Within a few days they start to develop stripes.

2nd or 3rd instar WBC larva (Photo Credit: T. Baute, OMAFRA)


To know for sure that they are WBC, watch how the way.  The itch their way along a leaf like an inchworm.  Click on video to see how they crawl.

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4 thoughts on “Young Western Bean Cutworm Larvae

  1. if you can almost see the larva in the silk of the corn will insecticides possibly get to them?

    1. Hi Dan

      If the majority of the larvae have already entered the ear than the insecticides won’t work on them. Correct insecticide timing is when the larvae have just hatched and are present on the whorl, tassel or leaves before they make it into the ear. Insecticides can’t penetrate the ear and these larvae don’t really feed on the outside of the ear again once they are safely inside feeding on the kernels.

  2. Hi, Tracey! Still lovin’ your Bug Blog.
    Any news on brown marmorated stink bugs? Also… Isolated fields in Iowa have had soybean aphid numbers jump to well over threshold. Most are holding at low levels. What are you seeing?

    1. Hi Kevin

      We have not found any BMSB in corn or soybean fields yet. The only known specimen to be found in Ontario so far has been in a home near Hamilton this spring. We are trapping and surveying but don’t expect it to be at pest levels for a few more years yet.

      As for soybean aphids, yes they are increasing here too. Eastern Ontario in particular saw numbers climb to above threshold very quickly last week, though I suspect more fields in Central and Southern Ontario will also have this happen. I was just about to write a blog about it actually so good timing on the question.

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