JAPANESE BEETLE
About
1/2 inch long, Japanese beetles are a shiny, metallic green with coppery
brown wing covers that extend almost to the tip of the abdomen. Small tufts
of white hairs occur at the tip of the abdomen and along each side. Eggs
are translucent white to cream and elliptical and about 1/16 inch in diameter
when first laid. In a few days, the egg becomes more spherical and doubles
in size. Grubs are white, slightly curled and have yellow-brown heads.
Grubs are about 1 inch long when mature. Unlike other grubs found in turf,
it has two rows of spines which form a "V" on the underside of the last
abdominal segment. The pupa is approximately 1/2 inch long and 1/4 inch
wide, and it gradually turns light brown and then develops a metallic green
cast.
First
reported in North America in 1916, the Japanese beetle now occurs in most of
the eastern United States. The beetles feed on over 275 different kinds of
shade and fruit trees, shrubs, flowers, small fruits, garden crops, and weeds.
Some of their favorites are roses, crape myrtle, grapes and fruit trees. Japanese
beetle adults eat flowers and foliage, leaving only a lacy network of leaf
veins. The beetle grubs are pests of the roots of grasses and shrubs. Japanese
beetle grubs occur in lawns, golf courses, pastures and even wooded areas.
They burrow through the soil consuming roots. Areas of dead grass may appear
when large numbers of grubs are present especially during dry spells in September
or early October. The grubs overwinter in cells about 6 inches deep. In spring,
they move almost to ground level, where they complete feeding and then pupate.
Adults emerge as early as mid May in eastern North Carolina. Peak emergence occurs in July. Throughout summer, the beetles attack the fruit and foliage of many plants. Soon after emerging, females deposit 40 to 60 eggs in small batches 2 to 3 inches deep especially in damp soil. During dry periods, adults may be more attracted to low lying and irrigated areas to lay eggs where soil moisture is higher. In extremely dry weather, many eggs and larvae perish. In warm, wet summers, eggs hatch in about 2 weeks. The newly emerged larvae feed until cold weather forces them into hibernation. One generation occurs each year.
Flowers and ornamental plants can be protected by dusting or spraying foliage with pesticide. For a list of susceptibility of certain woody ornamentals to Japanese beetle damage see the Mississippi State study.
For home use, carbaryl (Sevin), malathion, imidacloprid (Merit) are good choices. Many of the newer lawn and garden multi-insect products are also effective. Pyrethroid containing chemicals are slightly more persistant. Spinosad and Neem based products give a little protection. Roses or shrubs may also be protected by covering with light netting. Handpicking adults from plants is an almost hourly battle. Homemade concoctions and blended beetle cocktail repellants are mildly effective, and may need reapplication every one or two days.
Japanese beetle traps may catch up to 75% of the beetles that approach them. Traps may lower beetle populations from 30% (1 trap per acre) up to 39% (10 traps per acre) if placed throughout a neighborhood. The trapped beetles must be emptied from the traps every one to two days to prevent them from rotting and releasing ammonia which is repellant to other Japanese beetles. Traps are commercially available. Homemade traps are also effective in catching beetles if baited with phenylethyl proportionate plus eugenol lure available at garden centers and hardware stores. The traps are much more effective in attracting Japanese beetles than in trapping them. Consequently, traps should be placed as far away from the plants to be protected as possible. If traps are used, place far away from susceptible plants. Traps, alone, are not likely to give satisfactory protection to plants being eaten by adult Japanese beetles and pesticides may be required, anyway.
For commercial operations, imidacloprid, acephate, or pyrethroids are effective. Follow label directions for rates and safe use. It may be necessary to apply some of these pesticides more than once for complete protection during the weeks of adult feeding.
Grub control
Commercial preparations of the Bacillus popilliae (milky spore disease) offer some slight effect as a soil treatment. These spores infect and kill only Japanese beetle grubs. The spores are released into the soil and infect new grubs as they come in contact with the bacterial spores. Milky spore preparations can be applied from July until the first hard freeze to areas of turf grass that are mowed to 2 to 3 inches tall. These areas are preferred egg laying sites for adults and here, during the warm months, grubs feed close to the soil surface. Results of milky spore have been disappointing, however, and generally do not justify the expenditure. Milky spore treatment also provides little relief for the homeowner from the onslaught of foliage feeding by the highly mobile adults which fly into the area. Japanese beetle grub populations rarely reach economic threshold levels as turf pests in home lawns. A general threshold is 10 grubs per square foot (fewer on commercial turf) before turf damage becomes an issue. In addition, only small areas of the turf may be infested, so do not assume the entire area is infested. Heterorhabditis species of nematodes may be a viable non-chemical alternative for turf protection, but application directions must be carefully followed.
Soil insecticides for grub control are available, but rarely needed or justified for home owners. Imidiclporid-based insecticide applications any time from late spring through summer are fairly effective. The residual life of the soil applied chemicals varies, so follow the label instructions. Killing all grubs in a lawn will not protect your shrubs from Japanese beetle adult feeding so grub insecticides for adult beetle control are an unnecessary use of pesticide.
No matter which product or approach is selected, be sure to follow label directions. Recommendations for insecticides approved for control of these insects in home lawns can be found under the "White Grubs" listing in the Insect Control in Home Lawns section of the NC Agricultural Chemicals Manual. Recommendations for insecticides approved for use on sod farms, golf courses or other commercial sites can be found in the Commercial Turf Insect Control section of the NC Agricultural Chemicals Manual.
Useful References
Recommendations for the use of chemicals are included in this publication as a convenience to the reader. The use of brand names and any mention or listing of commercial products or services in this publication does not imply endorsement by the North Carolina Cooperative Extension Service nor discrimination against similar products or services not mentioned. Individuals who use chemicals are responsible for ensuring that the intended use complies with current regulations and conforms to the product label. Be sure to obtain current information about usage and examine a current product label before applying any chemical.
Published by North Carolina Cooperative Extension Service
Distributed in furtherance of the Acts of Congress of May 8 and June 30, 1914. Employment and program opportunities are offered to all people regardless of race, color, national origin, sex, age, or disability. North Carolina State University at Raleigh, North Carolina A&T State University, U.S. Department of Agriculture, and local governments cooperating.
Prepared by: James R. Baker & S. Bambara, Extension Entomologists
ENT/ort-44
July 1994 (Revised) April 2002
Web page last reviewed January, 2008 by the webperson.