Japanese Beetles – How to Control Them!

Are Japanese beetles making your green bean plants look worse than baby swiss cheese? For the last two weeks, I have been constantly picking beans and spraying Japanese beetles, which is why I haven’t blogged since then. They are becoming a problem for all of us and I will explain what you can do to prevent and or control them.

Unfortunately Japanese beetles are quickly becoming a nuisance to farmers, gardeners and landscapers. Over the last few years the pest has been making a steady migration. Japanese beetles are less than one half inch long metallic green beetles. The beetles have hard copper brown colored wing covers. An easy way to distinguish Japanese beetles from other beetles is the row of white tufts that protrude from underneath the wing covers and from the tip of the abdomen.

Another distinguishing characteristic for the Japanese beetle is the absence of foliage on your favorite plants coinciding with the presence of hoards of copulating beetles. Adult beetles emerge from the ground in late May and early June. Adult beetles live approximately 30 to 45 days. Heavy feeding pressure from Japanese beetles usually lasts from 4 to 6 weeks. By September damage from the beetles has usually slowed down significantly.

Japanese beetles are not picky eaters and will feed on over 300 species of plants. Foliage of roses, many tree fruits and grapes seem to be especially attractive to the beetles. The grubs of these beetles can also damage turf before they emerge in the spring. Japanese beetles are known to fly as far as 5 miles but one to two miles is more common. There migratory nature makes controlling the beetles very challenging.

Even if you kill every beetle on your property today, more may begin showing up immediately. Japanese beetles apparently produce aggregation pheromones which attract more beetles to feed and find potential mates. Additionally, beetles may be attracted by volatile odors produced by damaged plants. It is important to maintain low numbers of beetles. High beetle populations produce more pheromones and volatile oils and attract even greater numbers of beetles.

Many chemicals are labeled for control of Japanese beetles. I have heard several reports of good control being obtained from using the chemical carbaryl (sevin®). If you choose to use an insecticide be sure to follow the label instructions and keep up with the spraying. Whatever control strategy you implement, do it when you see a few beetles and before the pest is out of control.

Some grape growers have used a product made from a fine powder of kaolin clay called Surround®. I first heard of this product several years ago when it was being used for control of fungal diseases on apple trees. The product forms a thin protective layer on the trees limbs and leaves. In addition to stopping some fungal infections the product also seems to camouflage plants from Japanese beetles. If the product is applied before the arrival of beetles they never view those plants as food and simply move on to other food sources.

Kaolin clay products do create a haze on plant surfaces that is not aesthetically pleasing which makes it impractical for plants in a landscape setting. Small amounts of beetles on high value plants can be removed by hand. Neem extracts may deter Japanese beetle feeding but will probably not give adequate control when populations are high.

Direct spraying with insecticidal soaps can kill Japanese beetles on contact but will provide no residual protection. These beetles are another in the long list of trials that we gardeners are privileged enough to get to face. Like any trial we’ll come out of it better on the other end and undoubtedly have some good stories to tell about the process.

For pesticides, insecticidal soaps and all your gardening needs, click on Gardens Alive! Remember, they still have the $20 for $40 offer at checkout…so now is the time to buy!

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Happy Gardening from the Master Gardener Girl!!

One Response

  1. I do accept as true with all the concepts you have introduced for
    your post. They are really convincing and will certainly work.

    Still, the posts are too brief for beginners. Could you please lengthen them a bit from subsequent time?
    Thank you for the post.

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