You Are Here: Management Updates 2001 Archive June 26, 2001

Date: June 26, 2001
Category: Insects
Subject: Armyworms, Beetle Adults

We have been getting reports from southeastern Massachusetts that some home lawns are being inundated with caterpillars of some sort. We have not had specimens sent to us in Amherst, but based on the descriptions, I am guessing the lawns are being attacked by one of the species of ARMYWORMS. One species which has been active in Ohio already this spring is the armyworm (Pseudaletia unipuncta), and I suspect this may be the culprit in Massachusetts as well. Caterpillars of this species tend to be gray or green with a hint of pink, but they also have a distinct light-colored stripe along the side of the body. There is also a thinner dark stripe that includes the black spiracles on its lower edge. Caterpillars approach 1.5 inches before they begin to pupate.

Armyworms tend to move in large numbers (hence the name) and can be devastating in areas where they congregate. The damage can appear seemingly overnight, if one of these "armies" appears in an area. We do not know what conditions were so favorable this past winter or spring, but apparently we are in for quite an onslaught. (One homeowner reports 150 caterpillars in a square foot of what used to be turf!)

CONTROL OPTIONS are limited once caterpillars reach an inch in length. The good news is that most caterpillars of that size will be finishing their feeding fairly soon, so they will not continue to cause damage. However, you can figure they have some brothers and sisters along with them ... If desperation reigns, homeowners may try using a home lawn-approved insecticide that has armyworms on the label, but there are no guarantees. Armyworms normally are more active at night (believe it or not!), so applications made late in the day will be "fresher" when the caterpillars return to the surface to feed.

And JAPANESE BEETLE ADULTS have been reported flying this week (26 June). This is about a week earlier than we might normally expect to see the beetles, but the warm weather earlier in June probably pushed things along a little bit. Meanwhile we saw EUROPEAN CHAFER and ASIATIC GARDEN BEETLE ADULTS in Waltham earlier this week as well. For those who are planning to use a preventive grub material, you can figure that the European chafers (eastern third of Massachusetts in particular) will start laying eggs by the end of next week, so any time in the next two or three weeks would be a good time to apply materials like imidacloprid or halofenozide for that species. Japanese beetles probably won't start laying eggs for a couple weeks.

Welcome to summer!!!

- Submitted by: Dr. Pat Vittum