Home Meet our Bloggers. What Do Japanese Beetles Eat? Posted on December 5, by Bartlett Tree Experts. Japanese beetles devouring a leaf. About Bartlett Tree Experts. Posted in Pests and Diseases.
Some gardeners living with this pest refer to the riddled leaves on otherwise healthy plants as Japanese lace. Large populations can cause more severe damage resulting in brown and falling leaves. The immature beetles are grubs that feed on the roots of lawn grass and ornamental plants. You may notice small patches of the lawn turning pale and dying just like drought stress.
As the population increase, larger areas are damaged and the roots destroyed. At this point, the grass can easily be lifted from the soil. More damage occurs when skunks and raccoons move into the area digging and dining on these tasty grubs. This is often when I get the call to diagnose the lawn problem. They have coppery-brown wing covers and tufts of white hairs along the edges of their back making them easy to identify.
Japanese beetles start life as a white C-shaped grub. As soil temperatures warm to 50 degrees in spring they move closer to the soil surface and start feeding on plant roots. After several weeks they stop feeding, create a space in the soil and pupate, transforming into the adult beetle. The adult beetles emerge sometime in May in warmer regions and later in June or July in colder areas of the US and Canada.
Your local University Extension Office can help you narrow down the time to begin watching for this pest in your region. Or you can use growing degree days to calculate the beetles' emergence from the soil. This figure corresponds to the accumulation of warm temperatures needed for the beetles to reach the point where they are ready to emerge from the soil.
The daily numbers are added for a sum of the growing degree. Or you can just watch for their appearance in your garden. Much less math involved in that approach. The adults feed for 6 to 8 weeks or more.
They prefer moist lawn areas and mulched garden beds. The eggs hatch in several weeks and the small grubs begin to feed on grass and other plant roots. As soil temperatures drop in fall the full-size grubs move down through the soil for winter.
And the cycle begins again as the soil begins to warm in spring. Their populations do rise and fall over time and can vary throughout the area. You may have a large influx of these insects for several years followed by one with very few.
Enjoy the short break and be ready for an increase in the future. The adults can fly up to two miles traveling in from surrounding untreated spaces. Proper timing and application of the right product are critical for effective control.
Spring applications when grubs are large and mature grubs are not very effective at killing these. Milky spore is probably the most readily available organic grub control. I've found these horrid bugs on my hibiscus, marigolds, even basil!! I hope someday soon they make a "magic" spray for these things.
I will hand pick as many as I can. They love my zinnias. They are piled-up on each other on the blooms. Must be having a party! Have sprayed and also smash between my fingers. Never had them this bad before. They have ruined my roses. We used to put half an inch of Dove dish soap or Sunlight dish soap and a half an inch of vinegar in measuring cup and pour it into a quart of warm water and test spray some sample plants and leave them for a few days to test if the plant can tolerate it.
Then spray the whole plant and the ground around it. Then wait a minute and spray it all again. Or come back in an hour or the next day and spray again. This works on fruit trees too but always test spray first. You can use this spray for grass too. Test spray a small patch first to make sure your brand of grass will tolerate it. Got my introduction to Japanese Beetles this month.
Canas in a pot are covered in them. Hand pick everyday but am losing the battle. They especially. When I disturb them they fly off to my Boston Ivy vine.
Think I brought them home in purchased potting soil. In 25 years of living here this is a first for the little beggars. Your information said these beetles "generally" don't like eggplant, but I can tell you that they absolutely devoured my eggplant.
Thank you for your feedback! We have revised the text. Indeed, these beetles are not fussy eaters! They were really damaging my hazel trees earlier in the year, I wonder if Japanese gardeners have problems with these beetles, lol. I add a little detergent to the water and simply knock the darned beetles into the water. They can actually draw MORE beetles into your yard. If you have to use them place the bag in the back of your property, hopefully not near your neighbor's prized roses!
There is a Home Defence that contains product to kill Japanese Beetle works well. Also if you take a container of boiling water out and knock them into it it's instant gone especially if they are attacking your roses. You indicate a home defence that will work.
Can you be more specific? Thank you. Thanks for advice re: japanese beetles. They are eating my balsam fir trees. Needles are going brown.
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