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Vermont Garden Journal: Japanese Beetle Grubs

University of Illinois' Dixon Springs Agricultural Center, Ron Hines
Japanese beetles

I'm not going to get cute with this topic. There's nothing sweet about Japanese beetle grubs. We recognize grub damage as bare patches in the lawn. Of course, those grubs will turn into adult Japanese beetles in summer and devastate roses, grapes, and many other common garden plants.

While many gardeners despise the Japanese beetles and want to control them without using harmful sprays, the key to success is not attacking the adults, but the young. The c-shaped pale yellow beetle grubs are in the top layers of the soil right now. I know, I've been digging them up as I edge my beds. They will pupate soon and emerge as adult beetles. Now is time to attack the grubs. Luckily there is a control that seems to work well. Beneficial nematodes are microscopic, small roundworms that attack and parasitize beetle grubs in the soil. While nematodes are garden pests further South and West, these beneficial types just attack the soil borne grubs and don't harm plants, beneficial insects, pets or humans. Unlike the milky spore disease powder that also attacks Japanese beetles, beneficial nematodes seem to perform better in our cool soils. In field studies the various strains of beneficial nematodes reduced grub populations to levels comparable to that of the standard chemical insecticide.

The key to controlling the grubs is timing. Spray nematodes in June on lawn areas and mulched paths close to where the adult beetles were feeding last summer. That's where the eggs were laid and grubs live. Spray around dusk and keep the area well watered every 3 days. The beneficial nematodes use water channels to move in the soil looking for the grubs.

And now for this week's tip, watch my new video on vpr dot net backslash tours showing highlights of my upcoming Garden and Food Tour of Barcelona Spain and Provence France this September. We'll see Spain and France through a gardeners and foodies eyes, but sign up soon as the deadline is approaching.

Next week on the Vermont Garden Journal, I'll be talking about fragrant annual flowers. Until then, I'll be seeing you in the garden.

Broadcast on Friday, June 13, 2014 at 5:57 p.m. and Sunday, June 15, 2014 at 9:35 a.m.

IPM with Nematodes
Beneficial Nematodes

Charlie Nardozzi is a nationally recognized garden writer, radio and TV show host, consultant, and speaker. Charlie is the host of All Things Gardening on Sunday mornings at 9:35 during Weekend Edition on Vermont Public. Charlie is a guest on Vermont Public's Vermont Edition during the growing season. He also offers garden tips on local television and is a frequent guest on national programs.
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