The Japanese beetle was first detected in New Jersey in 1916. Since then, it has spread to much of the US, including much of New England. The life cycle of this insect typically takes 1 year to complete, however in the northern parts of New England, some Japanese beetle grubs may take 2 years to mature. In New England, partially mature grubs (larvae; immatures) overwinter in the soil below the frost line. In the springtime, grubs will continue feeding on the roots of grasses until they are ready to pupate near the soil surface. Adults are said to emerge in the third week of May in North Carolina, and the first week of July in parts of New York, Vermont, and New Hampshire (Johnson and Lyon, 1991). Adults also emerge starting in July in Massachusetts, over a two month period, which is thought to peak in early August (Robert Childs, Personal Communication). Adult beetles are approximately 1/2 inch long, stout bodied, with brown wing covers (elytra) and a metallic green body. Adult Japanese beetles will fly to trees, shrubs, and other hosts and begin feeding. Adults live for 30-45 days, and will mate over this time frame. After mating, females lay eggs approximately 1 to 4 inches beneath the soil surface. Females can each lay approximately 40-60 eggs. Eggs hatch in the next 2 weeks and small grubs begin to feed on fine roots until cold temperatures encourage them to burrow deep in the soil where they overwinter. Mature larvae are nearly 1 inch in length, white, with brown heads. Japanese beetle larvae resemble the grubs of other scarab beetles. Both the adult and larval stages are capable of seriously injuring plants.
The adult beetles skeletonize the leaves of many different plant species, including but not limited to the hosts listed above. Over 300 species of plants are listed as adult food sources. Seasonally, the adults may feed on low-growing plants first, such as roses, grapes, and shrubs before moving onto the foliage of trees. On trees, the leaf tissue between veins is fed upon, leaving behind a lace-like skeleton. They may prefer young leaves to old. On roses, even the flowers may be fed upon. The larvae (grubs) can be a serious pest of turf by feeding on the roots. Management information provided here is for the damage caused by the adult life stage to trees and shrubs. Consult UMass Extension's Turf Program for information about Japanese beetle grub feeding damage in turf.
Monitoring adults can be done with traps, but place them far away from valued plants. Trapping may not be effective in managed landscapes. Adults may prefer to feed during the warmest part of the day, especially on plants in full sun. Monitor for adults from late June to early August.
Pick and destroy adults feeding on trees and shrubs when practical by dropping them into a bucket of soapy water. Planting trees and shrubs that are not preferred by the Japanese beetle (when possible) can help reduce issues with this insect on specimen plants in managed landscapes. Trees and shrubs known to be less preferred by this insect include but are not limited to: arborvitae, boxwood, dogwood, forsythia, ginkgo, hemlock, hickory, holly, juniper, lilac, magnolia, northern red oak, red and silver maple, redbud, rhododendron, spruce, sweetgum, tuliptree, and yew. Keep in mind that these options may have other significant insect pests in your area. (Ex. arborvitae, boxwood, hemlock, magnolia, etc.)
Parasitic wasps have been important in managing Japanese beetle populations, including Tiphia vernalis and T. popilliavora. Istocheta (formerly Hyperecteina) aldrichi, a parasitic fly known as the winsome fly, has been important in reducing Japanese beetle populations in Massachusetts. A large array of additional insect natural enemies of Japanese beetles are listed in the Invasive Species Compendium; CABI. Birds and toads are predators of adult beetles and grubs. Grubs are also fed upon by moles, shrews, and skunks (Johnson and Lyon, 1991).
Acephate (NL)
Acetamiprid (L)
Azadirachtin (NL)
Bacillus thuringiensis subsp. galleriae (NL)
Bifenthrin (NL)
Carbaryl (L)
Chlorantraniliprole (NL)
Chlorpyrifos (N)
Chromobacterium subtsugae (NL)
Clothianidin (NL)
Cyantraniliprole (NL)
Deltamethrin (adults) (L)
Dinotefuran (NL)
Emamectin benzoate (L)
Entomopathogenic nematodes (L)
Fenpropathrin (NL)
Flonicamid+cyclaniliprole (N)
Gamma-cyhalothrin (L)
Imidacloprid (L)
Insecticidal soap (NL)
Isaria (paecilomyces) fumosoroseus (NL)
Lambda-cyhalothrin (L)
Malathion (L)
Neem oil (NL)
Permethrin (L)
Pyrethrin+sulfur (adults) (NL)
Chemical management information provided in this guide is for management of Japanese beetles on trees and shrubs only, not turf.
Active ingredients that may be applied systemically include: acephate (injection), acetamiprid (injection), azadirachtin (injection, soil drench), chlorantraniliprole (soil drench), clothianidin (soil drench), cyantraniliprole (soil injection, soil drench), dinotefuran (soil drench), emamectin benzoate (injection), imidacloprid (soil drench), and neem oil (soil drench).
When used in nurseries, chlorpyrifos is for quarantine use only.
Make insecticide applications after bloom to protect pollinators. Applications at times of the day and temperatures when pollinators are less likely to be active can also reduce the risk of impacting their populations.
Note: Beginning July 1, 2022, neonicotinoid insecticides are classified as state restricted use for use on tree and shrub insect pests in Massachusetts. For more information, visit the MA Department of Agricultural Resources Pesticide Program.
