The beasts are back – Japanese beetles return (and some good news)

Tue. Jul. 6, 2021
Topic:  Insects · Invasives

Click on the link below to listen to my 2 min. Garden Bite radio show: The beasts are back – Japanese beetles return (and some good news)

The beasts are back. I found my first Japanese beetles on my native Leadplant. Grabbed him, squished him. Then I wandered over to my roses and found 2 more. Two days later, there were 10 of them munching on the last of the roses on my ‘Music Box’ rose.

I’ve armed up with my bucket of soapy water.

the water was sudsy but the soap still kills ’em

Japanese beetles feed on the leaves, flowers or fruit of more than 350 species of plants. Great! JB were first discovered in Minnesota in 1968 and before that in parts of Wisconsin. From a few to millions, they have stuck around in zones 4 and warmer. While their numbers fluctuate each year, they’re still an issue.

The adults feed on flowers and foliage, the grubs feed on turf and ornamental roots.

Japanese beetles on my native Leadplant. They loved the flowers. ugh.

Japanese beetles were first found in the United States in 1916, after being accidentally introduced into New Jersey. Until that time, this insect was known to occur only in Japan where it is not a major pest.

While my soapy water in the evening method is okay, if you’re gone for a few days, your plants could be skeletonized.

Note, chemical methods also kill good bugs. Here is more from the University of Minnesota, which says the best time to apply insecticides for grubs is from mid-July until early September. Granular applied insecticides distributed on soil with a spreader are usually the best insecticides for JB.

NOW for the good news!!! This from Mary Schier of Northern Gardener magazine…

Photo by Mary Schier
Winsome fly on Japanese beetle

These are Mary’s words on the post she wrote:

Some good news on the Japanese beetle front, and I spotted it in a friend’s garden this morning. Those dots toward the front of the beetle are the eggs of the winsome fly, a parasite that acts as a biological control for beetles. The female winsome flies lay their eggs on the pronotum of Japanese beetles. A few days later, the eggs hatch and the fly maggots basically eat the beetle from the inside out.
Gardeners should watch for those distinctive eggs and let those beetles go to perpetuate the parasite. Beetles without dots should go into your bucket of soapy water.
Interestingly, the winsome fly was introduced in the U.S. in 1922 to control the beetles that had been accidentally released here in about 1918. It took the beetles about 50 years to get to Minnesota and the flies another 50 to follow them. It should be interesting to see what this does to Japanese beetle numbers.
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