The Japanese beetle is the most destructive urban and suburban landscape pest in the eastern United States. According to the National Agricultural Pest Information Service, Japanese beetles now occupy at least the eastern half the country, and they are steadily munching their way west at a rate of five to 10 miles per year.

Plant volatiles attract Japanese beetles,
resulting in feeding aggregations.

In a feeding frenzy that would do credit to a shark, this pest devours foliage and flowers of hundreds of plant species, from roses to apple trees, and wreaks havoc on turf in lawns, parks, and golf courses.
 

Beetles Swarm to Floral, Fruity Compounds

Research has shed light on what prompts Japanese beetles to act like "garden sharks." These pests swarm with killer instinct when they smell plants whose leaves release floral, fruity compounds under attack. As the scent is released, more and more beetles attack a plant, methodically stripping the flesh from between the veins of the leaves until the plant is little more than a skeleton.
    Researchers have tried many avenues to discourage this pest. Small-scale use of scented commercial traps proved counter- productive, attracting more beetles to a garden than might have shown up otherwise. Repellents based on neem oil, a natural botanical insecticidal, also provided little benefit, as did milky-spore powder, despite its long history of use. Mainly, homeowners and landscape managers in the past relied on repeated applications of synthetic insecticides to protect lawns and landscapes from this pest. Many of the effective products, however, are under regulatory scrutiny and may soon be prohibited or severely restricted.
    Soil insecticides are used to control insect pests in home lawns and on golf courses, but some lawn chemicals pose a potential environmental hazard or upset nature's balance by killing beneficial insects and earthworms.
 

Alternative Management Needed

Problems with pest resistance and concern for public safety and pesticides' environmental hazards have underscored the need for alternative, effective management.
    The need to develop sustainable approaches to urban plant protection from the Japanese beetle has been the impetus for major IPM research at the University of Kentucky.
    Kentucky entomologist Daniel Potter and his collaborators are studying the feeding habits of Japanese beetles to determine ways natural plant resistance can be substituted for insecticides. Their work has shown that, within generally susceptible plant species such as crab apples, maples, and lindens, certain cultivars are highly resistant to attack and are good choices for use in beetle-infested areas. Potter hopes that by studying the basis for this variation, other resistant cultivars can be developed.
 

Molt-Accelerating Compounds Effective

University of Kentucky researchers are working with industry to develop safer insecticides with new modes of action. Researchers have discovered, for example, that a new class of insect growth regulators is highly effective against Japanese beetle grubs.
    These growth regulators, called molt-accelerating compounds (MACs), mimic the grubs' natural molting hormone in order to induce a premature, lethal molt. Because vertebrate animals lack this hormone, these compounds are essentially nontoxic to humans and wildlife. The first molt-accelerating compound was marketed for use on lawns and golf courses in 1998, and it marks a new generation of effective, environmentally friendly lawn-care products.
    Managing Japanese beetles and other urban landscape pests requires proper timing, which can be difficult. Landscapes often contain dozens of plant species, each with specific insect pests only briefly vulnerable each year.
    The Kentucky researchers developed a simple management system by tracking, for three years, seasonal development of 33 important insect pests and 34 types of flowering landscape plants. Because there is a phenological (weather-related) correlation between particular insects and plants, this tracking yielded a calendar which can help the gardener or landscaper determine timing for insect management by simply observing flowering dates of familiar plants such as lilacs and dogwoods.
    This research is being publicized not only in scientific articles, but in trade magazines, gardening journals, popular press articles, and on the Internet.
    As a result of IPM research at the University of Kentucky, homeowners and landscapers throughout the eastern United States now have information enabling them to:

• select pest-resistant varieties of landscape plants
• use fewer pesticides yet still reduce pest proliferation
• take advantage of newer, safer insecticides.

Japanese beetles swarm with killer instinct when they smell plants releasing floral, fruity compounds.

Replicate of a field trial testing for variation in resistance of rose cultivars to Japanese beetle defoliation.

Japanese beetle grubs cause millions of dollars in damage to lawns, golf courses, and other turfgrass sites.

This work is partially supported by the U.S.Department of Agriculture Southern Region IPM Grants Program and by grants from the International Society of Arboriculture, the Horticultural Research Institute, and the United States Golf Association.
 

For more information contact:
 

Doug Johnson    Research and Education Center    P.O.Box 469    Princeton, KY 45245-0469    (502) 365-7541 ext. 214

B.C. Pass, Choir    Department of Entomology    University of Kentucky    Lexington, KY 40546-0091    (606)257-7450