Japanese Beetle, Popillia japonica
Order: Coleoptera
Family: Scarabidae
Description
The Japanese beetle is an invasive species in North America and native to northern Japan. In the United States, this pest is more prevalent in eastern states. It was first introduced to New Jersey and regulations and careful monitoring have restricted its establishment in western states. Adults have an oval body about 15 mm (0.6 inches) long, and male beetles are slightly smaller than females. It is generally metallic green with coppery brown wing covers, which do not quite cover the tip of the abdomen. There are six tufts of white hair beneath the forewings on the abdomen. The antennae are clubbed at the end and may spread to a fan-like form. The larvae are white grubs that measure about 2.5 cm (1 inch) long and tend to lie in a curved C-shape. They have a creamy white body with a dark head and well-developed legs on the thorax.
Quick Facts
- Japanese beetle adults feed on foliage and fruits of many fruiting trees and shrubs. Raspberries and blueberries are highly attractive to this pest.
- Japanese beetle larvae are white grubs that feeds on the roots of grasses.
- Adults are best controlled by handpicking or using certain insecticide sprays.
- Japanese beetle traps can capture many adults but have not been shown to reduce damage to nearby plants. Beetles are best controlled by handpicking or the use of certain insecticides.
Japanese beetle on grape leaf. Note the six tufts of white hair on the abdomen beneath the copper-colored forewings. These beetles cause significant defoliation and damage to leaves and flowers of many plants. Image credit: Clemson University – USDA Cooperative Extension Slide Series , Bugwood.org
White grubs (larvae) of the Japanese beetle. Image credit: David Shetlar, Ohio State University
Japanese beetles feeding. Image credit: Ada Szczepaniec, Colorado State University, Fort Collins, CO
Japanese beetles feeding on raspberries. Image credit: European and Mediterranean Plant Protection Organization, Bugwood.org
Japanese beetles feeding on raspberry foliage. Image credit: Whitney Cranshaw, Colorado State University, Bugwood.org
High density of Japanese beetles feeding on apple shoot. Image credit: M.G. Klein, USDA Agricultural Research Service, Bugwood.org
Japanese beetles feeding on grape foliage. Image credit: USDA ARS, USDA Agricultural Research Service, Bugwood.org
Japanese beetle feeding on blueberry foliage. Image credit: Jerry A. Payne, USDA Agricultural Research Service, Bugwood.org
Life history and habits
Japanese beetle has one generation per year. Adults may begin to emerge from the soil in early June and are usually most abundant in early summer – from late June through early August. Adults can attack over 300 plant species, including a wide variety of fruiting trees and shrubs including but not restricted to grape (Vitis spp.), cherry (Prunus avium), plum (Prunus domestica), raspberry (Rubus spp.), and blueberry (Vaccinium spp.). Japanese beetles are often found aggregating on the sunny sides of plant foliage, fruit, and flowers where they feed and mate. Feeding tends to begin near the tops of plants from mid-morning until late in the afternoon or longer, depending on temperature. Mated females seek areas where soil is suitably moist to lay a small cluster of eggs among plant roots. A total of 40-60 eggs may be laid by each female beetle, during her four-to-eight-week life span. Upon hatching from the eggs, the grubs (larvae) seek out nearby plant roots and feed. During the time Japanese beetles are in the egg and earliest grub stage they are quite sensitive to drying and may die if soils temporarily dry out during this period. The larvae continue to feed until soil temperatures drop to about 60°F (16° C) at which time the larvae move deeper into the soil where they remain through winter. Activity resumes as soil temperatures rise in spring and, after a feeding period of about 4-6 weeks, the larvae form an earthen cell and pupate. A few weeks later the pupal stage is completed, and the new adults emerge.
Injury
Adults feed on the leaves and fruit of many commonly grown fruit-bearing plants. Heavy feeding on grape can skeletonize leaves, which significantly reduces yields and affects plant growth. In addition, feeding injuries produced by Japanese beetle can result in secondary attacks by the green June beetle (Cotinis nitida) and secondary pathogen infections. Infestations on berries pose a contamination hazard during the harvest period.
While this pest does not typically injure apples, previously damaged fruit is susceptible to feeding by Japanese beetle. Stone fruits such as peaches and plums are more thin-skinned and susceptible to feeding injury, which appear as gouged, shallow patches. This pest prefers feeding on early ripened or damaged fruits, and many fruits can be injured under high Japanese beetle densities. During the ripening period, most of the fruit’s edible portion may be consumed, leaving only the core.
Monitoring
Monitoring should begin early in the growing season, and management can begin when the first beetles appear. Trapping can be used for management when the pest population is low or as a monitoring tool in areas where Japanese beetle is established. It is important to note that the lures degrade over time, and that adult beetles can migrate several hundred yards from neighboring areas.
Traps for Japanese beetle consist of a funnel on top of a cylindrical collection vessel containing floral volatiles and a female sex pheromone. These traps capture varying ratios of male/female beetles, with a greater proportion of males captured in the afternoon.
Under high Japanese beetle populations, the use of traps can lead to a “spill over” effect in which plants near the trap experience an increase in feeding and injury. Research has demonstrated that plants in residential landscapes infested with Japanese beetle experience substantially more feeding injury when one or more traps are deployed, compared with similar landscapes in the absence of traps. However, trapping with a 121-liter trash bin can help remove large quantities of beetles from the population and has been shown to reduce feeding injury on blueberry foliage.
Cultural control
Varieties that produce thin-skinned fruits are more susceptible to feeding injury than varieties that produce fruits with thicker skin. Regarding grapes, the leaves of Marquis, Reliance, Catawba, Concord Seedless, Concord, Edelweiss, and Einset grapes are less attractive to Japanese beetle than other varieties. Of these grape varieties, Concord appears to show little or no measurable effect to feeding, and young vines appear to be less susceptible to feeding injuries. Research also indicates that grapes can tolerate low to moderate defoliation. The berry variety Prelude is less attractive to Japanese beetle than Anne, Caroline, Dinkum, Heritage, and Himbo Top. The apple varieties Honeycrisp and Zestar! experience higher defoliation and beetle densities than other varieties. In addition, certain apple cultivars, such as Honeycrisp, are more susceptible to yield loss due to defoliation over consecutive years. In small fruit crops, UV-blocking high tunnels can be deployed as a physical barrier to prevent Japanese beetles from feeding on plants.
Hand picking
Hand picking beetles can often be effectively employed in small plantings to help reduce feeding injuries of Japanese beetles. The beetles can be easily picked or dislodged from plants or can be removed by shaking infested plants over a collecting container in early morning when temperatures are cool. To be effective, it is recommended that handpicking be performed daily. Since beetle flights peak at midday and plants are colonized in the afternoon, hand picking beetles in the evening will further optimize this approach by maximizing the number of beetles removed. Furthermore, removing beetles in the evening reduces overnight feeding, resulting in decreased emission of plant volatiles that would otherwise attract more beetles.
Biological control
Several parasitoids have been released in the United States for Japanese beetle control, including Tiphia vernalis and Istocheta aldrichi. Both species have been successfully released in the United States. Neither species is currently established in Colorado, nor are they commercially available. The Tiphia spp. are wasps that lay eggs on the larvae of Japanese beetles, while I. aldrichi is a fly that attacks adults. Istocheta aldrichi can kill adults of Japanese beetle relatively quickly, which can help limit the pest population.
Chemical control
Some insecticides commonly used for managing Japanese beetle include pyrethroids, organophosphates, carbamates, neonicotinoids, and anthranilic diamides. These different insecticides vary considerably in features such as how long they can persist and control beetles, what plants they can be applied to, whether they move systemically in the plant, and their degree of hazard to beneficial insects, notably pollinators. Insecticides that are highly toxic to bees and can persist long enough to kill insects for days are hazardous to foraging pollinators. Some insecticides, which are less toxic to bees or persist for only a short period, can be used on flowering plants if applications are made during early morning or dusk–when bees are not active and visiting plants. A couple of insecticides do not have restrictions for use on plants in bloom because they have very little, if any, toxicity to bees.
Given the high dispersal activity and wide variety of plant hosts, Japanese beetles will often reinfest areas treated with insecticides. In such instances, multiple applications may be needed, which can result in outbreaks of secondary pests such as mites, whiteflies, and scales, depending on the insecticide. Certain anthranilic diamides can be used to reduce defoliation of woody ornamentals and have low toxicity toward bees. Defoliation can also be reduced with treatments of pyrethrin, but this insecticide should not be applied during flower periods to minimize effects on pollinators.
Azadirachtin is derived from neem oil and acts as a feeding deterrent, and applications have been shown to deter feeding on Tilia cordata, a species of linden, up to 14 days after treatment. However, its effectiveness may be reduced after multiple applications since Japanese beetles tend to habituate after repeated exposure. Saponins are a class of plant defense compound that are especially abundant in Medicago spp. such as alfalfa (M. sativa). Laboratory and field research suggests that these compounds display repellent properties against Japanese beetles and may be incorporated into existing management programs. Foliar spray applications of Bacillus thuringiensis galleriae (Btg) may also suppress feeding of Japanese beetles but can be toxic toward lepidopteran species. Therefore, Btg should not be applied in landscapes with lepidopteran host plants, especially those of threatened or endangered species.
CSU Extension Fact Sheet
Download or view the CSU Extension’s PDF fact sheet for your reference.
References
Althoff, E., and K. Rice. 2022. Japanese Beetle (Coleoptera: Scarabaeidae) Invasion of North America: History, Ecology, and Management. Journal of Integrated Pest Management. 13(1): 1-11. Available https://academic.oup.com/jipm/article/13/1/2/6503655
Hahn, J. 2022. Japanese beetles in yards and gardens. University of Minnesota – Extension. Available https://extension.umn.edu/yard-and-garden-insects/japanese-beetles
Hammons, D., K. Kurtural, and D. Potter. 2010. Impact of insecticide-manipulated defoliation by Japanese beetle (Popillia japonica) on grapevines from vineyard establishment through production. Pest Management Science. 66:565-571. Available https://onlinelibrary.wiley.com/doi/epdf/10.1002/ps.1908
Iovinella et al. 2023. Antifeedant and insecticidal effects of alfalfa saponins in the management of the Japanese beetle Popillia japonica. Journal of Applied Entomology. 147: 651-660. Available https://onlinelibrary.wiley.com/doi/pdfdirect/10.1111/jen.13153
Pinero, J., and A. Dudenhoeffer. 2018. Mass trapping designs for organic control of the Japanese beetle, Popillia japonica (Coleoptera: Scarabaeidae). Journal of Pest Management Science. 74: 1687-1693. Available https://onlinelibrary.wiley.com/doi/epdf/10.1002/ps.4862
Redmond, C., L. Wallis, M. Geis, R. Williamson, and D. Potter. 2019. Strengths and limitations of Bacillus thuringiensis galleriae for managing Japanese beetle (Popillia japonica) adults and grubs with caveats for cross-order activity to monarch butterfly (Danaus plexippus) larvae. Pest Management Science. 76: 472-479. Available https://onlinelibrary.wiley.com/doi/epdf/10.1002/ps.5532
Shanovich, H., A. Ribeiro, R. Koch, and A. Nielsen. 2012. Seasonal Abundance, Defoliation, and Parasitism of Japanese Beetle (Coleoptera: Scarabaeidae) in Two Apple Cultivars. Journal of Economic Entomology. 114(2): 811-817.
Available https://colostate.primo.exlibrisgroup.com/discovery/fulldisplay?docid=cdi_openaire_primary_doi_dedup_db88664bc821d2f0aa36a52c5460f33a&context=PC&vid=01COLSU_INST:01COLSU&lang=en&search_scope=MyCampus_FC_CI_PU_P&adaptor=Primo%20Central&tab=Everything&query=any,contains,japanese%20beetle%20fruit%20pest
Switzer, P., and R. Cumming. 2014. Effectiveness of Hand Removal for Small-Scale Management of Japanese Beetles (Coleoptera: Scarabaeidae). Journal of Economic Entomology. 107(1): 293-298.
USDA. 2015. Managing the Japanese Beetle: A Homeowner’s Handbook. United States Department of Agriculture – Animal and Plant Health Inspection Service. Available https://www.aphis.usda.gov/plant_health/plant_pest_info/jb/downloads/JBhandbook.pdf