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Japanese Beetle Info

July 24, 2003

 Japanese beetles pose a threat to many plants in our landscapes. The following information about Japanese beetles may help many of you who are finding the beetles this summer.

Japanese beetles were accidentally introduced into the United States and were first noticed in New Jersey around 1916. From this time they have spread throughout the eastern part of the country with few or no predators. Populations in Iowa are increasing rapidly as the pest makes its way across the country. Adult beetles feed during the day on several hundred species of fruit trees, ornamental trees, shrubs, vines, flowers, and field and vegetable crops. They devour flowers, fruit and many other tender leaves. Large holes or skeletonized leaves are trademark destruction as they feed on the tender parts of foliage between leaf veins.

How To Recognize the Japanese Beetle's Life Stages
The adult Japanese beetle is a little less than 1/2 inch long and has a shiny, metallic-green body and bronze-colored outer wings. The beetle has six small tufts of white hair along the sides and back of its body under the edges of its wings. The males usually are slightly smaller than the females. You are most likely to see the adults in late spring or early summer. During the feeding period, females intermittently leave plants, burrow about 3 inches into the ground--usually into turf--and lay a few eggs. This cycle is repeated until the female lays 40 to 60 eggs.

By midsummer, the eggs hatch, and the young grayish-white grubs in the common C-shape begin to feed. Each grub is about an inch long when fully grown and lies in a curled position. In late autumn, the grubs burrow 4 to 8 inches into the soil and remain inactive all winter. This insect spends about 10 months of the year in the ground in the larval stage, causing tremendous damage to the roots of plants and turf with its voracious appetite. In early spring, the grubs return to the turf and continue to feed on roots until late spring often destroying turf in lawns, parks and golf courses. Then they change into pupae. In about 2 weeks, the pupae become adult beetles and emerge from the ground. This life cycle takes a year.

Controlling Adult Japanese Beetles
Peck’s carries the following products that list Japanese beetles as their target, and are most effective at killing or controlling the pests:
· Bonide Eight Insect Control Garden & Home: This product comes as a ready-to-use spray, concentrated spray, and a dust. It is very versatile and can be used on a very wide variety of plants. The spray form of this product is the most effective in controlling the beetles.
· Bonide Malathion Insect Control: This product comes as a concentrate to dilute to make a spray. Mix 1 to 4 teaspoons per gallon of water depending on what variety of plant you are spraying.
· Safer Japanese Beetle Traps: These traps use a dual lure bait of Japanese beetle floral lure and Japanese beetle sex pheromone to attract the beetles. The trap portion of the product then consists of a bag that prevents the beetles from getting out. Replacement bags and bait are also sold. Traps are placed at a rate of 1 trap per 50 linear feet, hanging 3-5 feet above the ground. Bags must be replaced when full. Remove the traps when the pest problem is taken of, as you do not want to attract more beetles to your yard with the floral lure and pheromone bait.