Nature Friday: Got Japanese Beetles?

I do not garden. I love them but I don't do the work. So when I see Japanese beetles, I don't get upset. I actually love photographing them. They are lovely and peaceful. They run away from bumble bees in flowers, co-exist with other flower flies in flowers, and they help each other when one falls off a plant. Click on this photo to see it large and perhaps you'll see why I photograph them: the glorious metallic colors, the furry tiger stripes, the forked antennae, and the textured elytra. 

Japanese Beetle (Popillia japonica)

My buggy research friend JF, however, is a gardener. She hates them. When she described to me what they do, I could understand why the contempt. The gardeners among you can understand, also. JF told me how you cannot get rid of them. But then she also mentioned winsome flies and asked me if I had seen any fly eggs on my JBs (Japanese beetles). JF sent me an article from Maine about winsome flies helping to control JBs without chemicals.

JF and I had one problem though: was the fly here? Our winters are severe in the northeast corner of Vermont. Many times, it's -30°F (-35°C) with wind chills much lower. Many insects cannot successfully overwinter here. My task was to photograph as many JBs as possible to find any winsome fly eggs. And I found them! So now we know winsome flies are here. You don't even have to find the actual fly, which is very small. You only need to see the white dots. Not the white dots that naturally run around the body of the beetle. Look at the front end, around the head, where they are usually laid by the fly.

Winsome fly eggs (Istocheta aldrichi)

The winsome fly was brought to North America purposefully in 1922 to parasitize JBs. It hasn't worked out that well because the fly's lifecycle has to coincide with the beetle lifecycle. It coincides here where I live, which is why I have the white eggs on the JBs. But in New Jersey? No. The fly has finally reached Vermont, Québec, and Ontario. It does not seem to be harmful to other parts of our environment. 

 

Range map of winsome fly

If you live in the areas shown on the map, and manually pluck the beetles from your garden, this advice from Maine may help you: 

• If you can, put in some plants that JBs avoid. Replace them with plants that are nectar-rich for the winsome fly adults and other JB predators.
• If you can, eliminate those plants that JBs most love.
• Encourage winsome flies by letting infected JBs free and only drowning the un-infected ones. The eggs can hatch only on beetles that are alive and then they can grow up to parasitize more beetles (see articles for lifecycle details).

Here are the references you may want to read:

1. Maine.gov: "The Fly that Attacks Japanese Beetles"
2. Laidback Gardener: "Plants Japanese Beetles Tend to Avoid"
3. Laidback Gardener: "The Fly that Attacks Japanese Beetles"

Maine says that by doing these things, ". . . you’ll find the number of beetles can drop significantly in just a few years. Many gardeners in areas where the winsome fly is well established say they can now garden much like they used to before JBs appeared, since the few remaining ones do little damage."

I hope you have a gardenful weekend!

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