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Management Updates: Jul 20, 2017

Parasitized Japanese Beetles, Green June Beetles
Jul 20, 2017

Parasitized Japanese beetle

When I got out of my car Tuesday afternoon (18 July), I noticed a Japanese beetle adult on the driveway. On closer inspection, it was barely alive. When I looked on the thorax, sure enough, there was an egg of the "winsome fly", a parasitic fly that lays eggs on Japanese beetle adults. The egg hatches into a larva that burrows into the body of the beetle and kills it within a few days, certainly before the beetle has a chance to reproduce.

About 15 years ago, I collected thousands of Japanese beetle adults from Suffield CT and brought them back to Amherst. We checked each one and saved the ones that had parasite eggs, and killed the others. We released the parasitized ones in the Amherst area, and hoped some of them would spread the parasitism. It is always gratifying to find a parasitized beetle in the Pioneer Valley.

The take home message - when you trap Japanese beetles, check to see whether any are parasitized. If they are, release them (a long way away from the trap!!!), so they can continue parasitizing beetles.

Green June beetle

Earlier this year I mentioned that my neighbors had brought me a grub that looked like a green June beetle grub. (These grubs resemble Japanese beetle and other white grubs in some ways, but are larger than European chafers, do not curl up at rest, have a slightly enlarged tail end, and crawl on their backs to move around. They prefer organic matter, and this grub had been found in a compost pile.) Yesterday my neighbors greeted me with a large beetle adult - sure enough, it was a green June beetle!

I don't believe this species has been confirmed in Massachusetts previously, but it is not surprising. The beetles have been found in Connecticut for several years, and with changing climate conditions, it stands to reason that these beetles are figuring out a way to survive in Massachusetts.

The adults are sometimes called "fig eaters" (as is a very closely related species). They are nearly an inch long and are described as a velvet green on the underside. The elytra (hardened wings) are a shiny green with a greenish yellow on the outer margins. They feed on organic matter, including ripening or overripe fruit. The life cycle is very similar to that of annual white grubs (e.g., Japanese beetle), and my guess is that the adults will be laying eggs soon. Most of the damage from the grubs is caused by their tunneling and burrowing through the soil and thatch zones, as they crawl to the surface at night to feed on dead and decaying matter.

Given that this appears to be a fairly new infestation, I doubt many of you will have to deal with them. Be forewarned though - some of the control options are very efficient and result in large numbers of grubs dying on the surface. While that might be satisfying to some, it leads to a smelly disposal problem!

Submitted by: Dr. Pat Vittum