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Japanese Beetles Land in the U.S.

1-800-PEST-CONTROL is your Japanese Beetle specialist. Quick identification and eradication is key to keep your valuable lawn and landscaping green and healthy.

The Japanese beetle is probably the most destructive pest of plants and lawns in the eastern United States. Japanese beetles were first found in the U.S. in 1916, after being accidentally introduced into the port of New Jersey. Until that time, this insect was known to occur only in Japan where it is not a major pest.

The U.S. provides a favorable climate, large areas of turf and pasture grass for developing grubs, hundreds of species of plants on which grubs adults alike can feed, and no effective natural enemies. The beetle thrives under these conditions and has steadily expanded its territory.

Japanese Beetles Description and Habits

The egg laying begins soon after the adults emerge from the ground and mates. In the afternoon females burrow 2 to 3 inches into the soil in a suitable area, and lay their eggs. The developing beetles spend the next 10 months in the soil as white grubs. The grubs grow quickly and by late August are almost full-sized (about 1 inch long). Grubs feed on the roots of turf grasses and other vegetable and plant seedlings. Japanese beetles can survive in almost any soil in which a plant can live.

Mid-summer rainfall and adequate soil moisture are needed to keep eggs and newly-hatched grubs from drying out. Females are attracted to moist, grassy areas to lay their eggs. Lawns and golf courses often have very high grub populations. Older grubs are relatively drought resistant and will move deeper into the soil if conditions become very dry. Japanese beetle grubs can withstand high soil moisture, so excessive rainfall or heavy watering of lawns does not bother them.

As Japanese beetle grubs chew off grass roots, the ability of the grass to take up enough water to withstand the stresses of hot dry weather is greatly reduced. Large dead patches will be seen in grub-infested areas. The damaged sod has no roots and can be rolled back like a carpet to expose the grubs. At this point, it may be too late to save the turf. Early recognition by 1-800-PEST-CONTROL of the problem can prevent this from happening to you homes lawn.

Japanese beetles over the winter are only present in the grub stage. When the soil cools to about 60°F in the fall, the grubs begin to move deeper underground. Most pass the winter 2 to 6 inches below the surface, although some may go as deep as 8 to 10 inches. Grubs become inactive when soil temperature falls to about 50°F.

When the soil temperature climbs above 50°F in the spring, the grubs begin to move up into the root zone. Following a feeding period of 4-6 weeks, they emerge as adults.  Adult Japanese beetles are 7/16-inch long metallic green beetles with copper-brown wing covers. A row of white tufts (spots) of hair protrude from under the wing covers on each side of the body. Activity is most intense over a 4 to 6 week period beginning in late June, after which the beetles gradually die off. Individual beetles live about 30 to 45 days.

They begin feeding on plants in June. Japanese beetles feed on about 300 species of plants, devouring leaves, flowers, and overripe or spoiled fruit. Adults feed on the upper surface of foliage, chewing out tissue between the veins. This gives the leaf a lacelike or skeleton like appearance. Trees that have been severely injured appear to have been scorched by fire. Japanese beetles are known to eat rose petals and leaves with delicate veins.

They usually feed in groups, starting at the top of a plant and working downward. A single beetle does not eat much; it is group feeding by many Japanese beetles that result in severe damage. The beetles are most active on warm, sunny days, and prefer plants that are in direct sunlight. Adult Japanese beetles are highly mobile and can infest new areas from several miles away. Usually, however, they make only short flights to feed or lay eggs.

Japanese Beetle Control

From a management standpoint, it is important to recognize that both the adults and grubs can cause severe damage. Since Japanese beetle adults are capable of flying in from other areas, controlling one life stage will not prevent problems with the other. Japanese beetle control during the grub stage requires properly timed applications of a soil insecticide by 1-800-PEST-Control to the infested turf. 

Proper Plant Selection to Avoid Japanese Beetles

Careful selection of plant species when replacing or adding to your landscape is the key to avoiding annual battles with Japanese beetles. Some plants and grasses are highly preferred by the adults and should be avoided. Plants that are especially prone to damage include; roses, grapes, lindens, sassafras, Norway maple, Japanese maple, purple-leaf plum, and others. Many varieties of flowering crabapples are also severely attacked by the beetles.

Many common trees and shrubs are much less attractive to Japanese beetles. These types should be considered when selecting plants and trees in Japanese beetle-infested areas.

Japanese beetles are also fond of certain weeds and non-cultivated plants such as bracken, elder, multiflora rose, Indian mallow, poison ivy, smartweed, and wild grape. Elimination of these plants destroys another feeding ground for these pests. Contact 1-800-PEST-CONTROL if you see Beetles or grubs in your yard or landscaping.

Japanese Beetle Traps

Japanese beetle traps are sold in many home and garden centers. The traps attract the beetles with two types of baits. One mimics the scent of female beetles and is highly attractive to males. The other bait is a sweet-smelling food lure that attracts both sexes.

Extensive research has shown that the traps attract many more beetles than are actually caught. Plants along the flight path of the beetles and in the vicinity of traps will likely suffer much more damage than if no traps are used at all. In most situations, use of Japanese beetle traps will do more harm than good. Call 1-800-PEST-CONTROL today for proper treatment methods.

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