Japanese Beetles

July 15, 2010 2 Comments

This…

Japanese Beetle

… is not welcome in my garden.

This is the Japanese Beetle, not to be confused with the Asian Lady Beetle…

Asian Lady Beetle

Chances are if you haven’t seen the Japanese Beetle in your garden yet, it will be there soon.  They have been reported in 44 of Iowa’s counties since 1994. 

Map from Iowa State University Extension

If you are in a county not shaded in red and you find a Japanese Beetle contact your local Extension office.

They were transported into New Jersey with ornamental plants from Japan in about 1916 and have been spreading ever since. 

Adult Japanese beetles are around from late June through August, about 6 weeks.  The adults lay eggs in July and August in grassy areas, and these eggs then hatch into white grubs that feed on plant roots and organic matter in the soil.  The grubs stay in the soil until the following June when they become new adults and emerge from the soil to start the cyce again.  Now, while you can treat your lawn for grubs, the female Japanese beetle lays her eggs in grassy areas over a LARGE area, not just your lawn. 

And they are hungry little buggers.  They feed on leaves and fruits (and the flowers) of over 350 kinds of plants.  I found one on my Butterfly Bush, the neighbors asparagus and several on our basil, chokeberry and hibiscus.  They are apparently especially fond of roses, raspberry, grape leaves and crabapple and linden tree foliage.  I don’t have a linden but they haven’t attacked our grape leaves, raspberries or our crabapple yet.  However, they have decided a couple of my roses are their favorite places to dine out.  I have seven separate rose bushes, not including the roses we got from our friend Bill many moons ago.  The beetles love my Sven rose bush…

These two are trying to enjoy a breakfast on my Sven rose bush.

and they have taken bites out of the Firefighter…

The result of a beetle munching on my rose...

World War II….

This one is working away on the leaf of my World War II rose

and Strike it Rich roses.

Before the "invasion". Actually, they only got a couple, but she is loaded again with buds, so I have to stay on top of it. Too bad I have to work so early in the morning. I could really get them taken care of!

I have found them on my Pink Knock-out….

I took this picture and then realized that the round thing on the right is a spider that has snagged this beetle for himself. I left it for him to enjoy.

and my miniature chinese rose, too.  (I can’t find a picture that doesn’t have it buried for winter, sorry)

They seem to be leaving my Ole rose (yes, he is Sven’s “brother”) alone.  It is on the other side of the house and that may make the difference, but they were on the chokeberry bush just to the east…. hmmm.

Controlling the adult beetles is rather hard to do because they emerge daily for several weeks.  I have been able to get a lot of them by handpicking, but a word of warning…  They tend to drop if they feel threatened, so I have had to get my hand or the bucket under the flower or stem I am grabbing.  Oh, and they can also fly. 

My weapon of choice against the Japanese Beetles. They haven't bitten or stung me, but they do leave a bit of, um, gunk on the gloves when they get squished. You can also just brush them into a bucket of soapy water.

The early morning seems to be the best time to get them since they appear more sluggish.  You can use Sevin, Eight or Tempo to spot spray infested foliage but multiple applications are required to keep control.  And make sure to only use them according to label instructions.  AND… spraying the adult stage doesnt’ control the larval stage (they tend be grubs in the turf) with grub damage to the turf and treatment of the turf doesn’t prevent adult damage to ornamental plants.  Tree foliage can be protected with a soil-drench application of a systemic insecticide (this works through the roots of the plant), but make sure you apply it several weeks ahead of the beetle emergence.  I used a systemic on my roses, but I didn’t get it on in time.  The beetles appeared within two weeks of my application.   Again, some of the tastiest morsels for the Japanese beetle appear to be peach, cherry (haven’t see any on mine, yet), plum, apple, linden, birch (again, none yet), elm, Norway maple, horse chestnut, willow, grape (not yet), raspberry (not yet), Virginia creeper, rose (oh, yes!), hollyhock, hibiscus, dahlia and zinnia.  Now, I will say that I treated our trees this spring with a systemic so that may have been enough to keep the beetle at bay.

There is some hope….  Japanese beetles rarely attack red maple, magnolia, white oak, red oak, common lilac, burning bush, hydrangea, forsythia, rhododendron, boxwood, holly, juniper, arborvitae, yew, fir, spruce, pine, impatiens, begonia, ageratum, columbine, sedum, coral bells and coreopsis.  And, for some reason, they have left our “Bill’s roses” alone.  It may be that they finished blooming before the adults emerged and therefore don’t taste as good.  I don’t know, but I keep checking, just in case….

Oh, and there are supposed traps out there (floral lure and sex attractant), but I wouldn’t use them.  The University of Kentucky did some research that showed the traps attract more beetles than they catch and that plants near the traps may have more damage than if no traps are used at all. 

So get out there and get rid of those Japanese beetles!

And Dig it!

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  1. JK says:

    We have a bug bag out for the Japanese Beetles hanging in our maple tree and I think I have the entire neighborhoods beetles coming into my yard. It has trapped a lot of them but I think they are right, it does “attract” them. But without it I think my maple tree would be bare.

  2. Rebecca says:

    I have them in my zucchini. They have destroyed over 10 plants in short time. They release the floral sex hormone/scent when killed in the soapy water. I make sure to remove the water immediately after or the next day there is as many bugs as I pull out. It is infuriating. I like the idea of attracting some of the birds. That will be my goal for next year.

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