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Attack of the Japanese Beetles
Attack of the Japanese Beetles
By Chuck Burgess, Information Specialist
Clemson Extension Home & Garden Information Center
Any day now, if not already, Japanese beetles will emerge and search out their favorite foods, in an effort to satisfy their seemingly insatiable appetite. They will gather on roses, cherry trees, crepe myrtles and even poison ivy for several weeks and then disappear sometime in August.
Japanese beetles have not always been a nuisance in the United States. They are native to Japan and were first observed in New Jersey in 1916. They are now pests in at least 24 states and continue to spread at a rate of 5-10 miles per year.
The adult Japanese beetle is a brightly colored, oval insect, not quite ½ inch long. The body and legs are a bright metallic green and the wing covers are coppery brown. It can be distinguished from similar beetles by the 12 white spots or tufts on the sides and tip of the abdomen.
Japanese beetles feed on over 400 species of plants. They seem to be attracted to plants in direct sunlight, where they skeletonize the leaves by chewing out the tissue between the veins.
Although a challenge, it is possible to protect your favorite plants from the beetles. Individual shrubs and small trees can be covered with netting. Chemical controls include carbaryl, (Sevin), malathion, cyfluthrin (Bayer Advanced Garden Rose & Flower Insect Killer) and esfenvalerate (Ortho Bug B Gon Garden and Landscape Insect Killer). Always read the label and know that during peak activity, foliage will need to be sprayed weekly to provide protection. Also, spray blooming plants early in the morning or late in the evening to avoid harming bees, which are a much needed pollinator.
It should be noted that most plants can tolerate moderate defoliation. Therefore, if the plant’s appearance is not a concern, the beetles can be merely tolerated or picked off by hand. Picking is most easily done early or late in the day when the beetles are not as active and dropping them into a bucket of soapy water provides for a quick kill.
Japanese beetle traps are very attractive to the beetles but unless many traps are concentrated in a community, they will not provide control. In fact, one study showed significant increase in plant damage when traps were placed adjacent to susceptible plants. The fact is, many beetles will land on nearby shrubs or trees before moving to the trap. If traps are used, place them 30 feet from the plants to be protected.
Many people are surprised to learn that due to larval activity, the Japanese beetle damages plants above and below ground. In July, the adult Japanese beetles burrow 2-4 inches below the soil surface and lay clusters of eggs. The larvae hatch in about 10 days, move into the root zone and begin feeding on the roots of grasses and other plants. Heavy feeding takes place in late August and September. The grubs spend the winter deep in the soil and move back up into the root zone in the spring when they resume feeding. In late April, pupation begins and is followed by the emergence of adults in May and June.
A high grub population is indicated by areas of yellowing and browning turf. This is most common in the late summer and early fall, when heavy feeding occurs. You may also find small holes in your lawn from skunks and other mammals that enjoy eating them. To check for grubs, cut 3 sides of a 1 foot square in the lawn and use a shovel to peel it back. Examine the soil and roots in the top 2 to 4 inches. Repeat this process in several locations. Control is recommended if you find an average of more than 6 grubs per square foot.
Caution should be taken when selecting products for grub control. There is at least one product carried by retailers with a picture of a grub on the bag. However, the active ingredient in this product (lambda cyhalothrin) binds tightly to organic matter and will not move below the surface. Such products will control turf feeding insects but not subsurface insects.
Products containing carbaryl (Sevin) or trichlorfon (Dylox) have an immediate effect and should be used when grubs are feeding. Products containing imidacloprid or halfenozide are considered preventive and are applied in May to control grubs in the fall. Grub-Ex and Bayer Advanced Season Long Grub Control contain one of these active ingredients. Best results are obtained when the insecticide is washed into the soil immediately after application.
Lastly, Japanese beetle larvae are highly susceptible to milky spore disease. It is caused by the bacteria, Bacillus popillae, which is contained in the product, Milky Spore. It is applied to the lawn as a powder. Complete control is not achieved for 2-3 years but once the bacterium is established in the soil it provides control for 20-30 years.
For more information on Japanese beetles, contact Marion County Extension office (423-8285) - or - Clemson’s Home and Garden Information Center at 1-888-656-9988 or http://hgic.clemson.edu.
Last update4/24/2008
This website is maintained by Marion County Extension.
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