How to Get Rid of Japanese Beetles Without Making It Worse

Japanese beetles are the rare garden pest where the obvious product makes things worse and the most popular organic fix has the weakest evidence. Below is what extension entomologists recommend, plus our own analysis of when and where the beetle is being recorded.

What works, what does not, and why

Know the beetle and its calendar

The adult is about 7/16 of an inch long (8 to 11 mm in the UF/IFAS description), metallic green with coppery brown wing covers, and has five tufts of white hair along each side plus a pair at the tip of the abdomen. The grub is a C-shaped white grub about an inch long when grown.

There is one generation a year. Adults start emerging in June (from mid-May in warmer areas, according to UF/IFAS), activity is most intense over a 4 to 6 week period beginning in late June, and individual beetles live about 30 to 45 days. Females slip into moist turf in the afternoon, burrow 2 to 4 inches down and lay a total of 40 to 60 eggs over their lives. The grubs feed on roots, overwinter 2 to 6 inches down and finish feeding in spring; USDA APHIS notes the insect spends about 10 months of the year underground.

Our analysis of 60,200 US research-grade iNaturalist records shows how compressed the adult season is. On our seasonality index (100 is the beetle’s average share of everything recorded), records sit at 11 in May, jump to 273 in June, peak at 577 in July, then fall to 247 in August and 73 in September. Ninety-three per cent of all the records fall in June, July and August. May and June beetles, the brown beetles that hit lit windows, peak earlier, in April and May, which is one quick way to tell the two apart. If those are what you have, see our guide to June bugs.

Step 1: Remove beetles by hand every morning

Handpicking works better than it looks. Kentucky entomologists note that beetles on a plant attract more beetles, apparently through odours from damaged leaves, so clearing a plant early stops the snowball.

1. Go out early, when it is cool and the beetles are sluggish.
2. Hold a container of soapy water under the stems and give the plant a sharp shake or tap. Japanese beetles play dead when disturbed and drop straight down, which Colorado State describes as thanatosis.
3. Repeat daily through the flight.
4. Pick off overripe or damaged fruit on fruit trees and the ground beneath; APHIS notes its odour draws beetles in.

For roses, small fruit bushes and young trees, Kentucky suggests cheesecloth or fine netting during the peak weeks.

Do Japanese beetle traps work?

They catch beetles. They do not protect plants. The commercial traps combine a sex lure that mimics virgin females with a floral lure that attracts both sexes, and Kentucky notes the combination can draw in thousands of beetles a day. University of Kentucky research by Gordon and Potter, published in the Journal of Economic Entomology in 1985 and 1986, found traps attract many more beetles than they catch, so susceptible plants along the flight path and near the traps suffer more damage than if no trap were used. Kentucky’s conclusion: in most landscape situations traps probably do more harm than good. APHIS notes a trap captures only about 75 per cent of the beetles that approach it, even under favourable conditions.

There is one exception the top-ranking advice leaves out. Where the beetle has only just arrived and the population is small and isolated, mass trapping can help. A Minneapolis study published in the Journal of Arboriculture in 1998 reported a 97 per cent reduction after four years of trapping an isolated population, and state agencies use trapping as part of eradication. That is a coordinated programme across an area, not one trap by a rose bed. If you keep a trap, put it well away from gardens at the edge of the property.

Step 2: Spray only what you must, and protect the bees

When beetles are on a tree too tall to shake, or numbers are overwhelming, a foliage insecticide is the remaining option.

• Check the label for the plant. It must list the plant or crop you are spraying, and for food plants, the days between the last application and harvest. Our guide to reading a pesticide label shows where to find both.
• Mind the flowers. Colorado State lists carbaryl, bifenthrin, beta-cyfluthrin, lambda-cyhalothrin, permethrin and imidacloprid as highly toxic to bees and persistent enough to kill them for days; their labels normally prohibit use on plants in bloom that attract bees. That matters because favourite hosts like roses and lindens are often flowering when the beetles arrive.
• Shorter-lived options such as pyrethrins and azadirachtin (neem) can be used on flowering plants only at times bees are not visiting, typically dawn or dusk, as the label directs. Expect only a few days of protection. Our review of neem oil covers the field trials.
• Expect to repeat. New beetles fly in throughout the flight, and Kentucky notes applications may need repeating during the adult period.

For large shade trees, spraying the canopy safely is generally a job for a licensed arborist or tree care applicator with the right equipment, not a garden sprayer.

Step 3: Deal with the grubs only if a count says so

Treating the lawn will not protect your roses. Colorado State says grub control in a yard has very little, if any, effect on the number of adults feeding on trees, shrubs and garden plants, because the beetles that eat your plants usually flew in from elsewhere.

APHIS gives the method. Cut a sample of turf 8 by 8 inches and 3 inches deep, count the grubs, multiply by 2.25 to convert to a square foot, and consider treatment where the count exceeds 10 grubs per square foot. Sample in late summer (August to October) or late spring (April to June). Our lawn pest control guide covers the full sampling routine and how thresholds differ between grub species.

• Preventive products applied just before or shortly after eggs hatch, typically mid-June to early July in Colorado State’s guidance, give the best results. They often disappoint when used as a late rescue on large grubs.
• Nematodes (Heterorhabditis bacteriophora is the commercially available species APHIS names) work when grubs are present and active, applied in cool, overcast conditions and watered in immediately. They are alive, so use them quickly.
• Let the surface dry in July. Colorado State notes eggs and the tiniest grubs are very susceptible to drying, and suggests letting the top couple of inches of soil dry a bit during egg laying and hatch in July and early August; UF/IFAS notes that in dry summers females seek out irrigated lawns to lay eggs. Deep, infrequent spring watering helps the grass tolerate it.
• Mow higher. Taller turf has a larger root mass and tolerates grub feeding better.

Skunks, raccoons and moles dig for grubs, and that digging is often the first sign. Damaged sod also lifts away like carpet because the roots have been cut.

What about milky spore?

Milky spore, a bacterium that causes milky disease in the grubs, is the most recommended organic fix and has the shakiest record. APHIS says it builds up slowly, over 2 to 4 years, and works best in community-wide programmes. Field trials by Redmond and Potter at the University of Kentucky, published in 1995, found neither the traditional spore product nor a newer formulation raised milky disease levels or reduced grub numbers on two golf courses over several years. Purdue says commercially available products have not proven effective, and Colorado State estimates that where it has long been present it reduces populations by less than 5 per cent.

Japanese beetles on trees, in the garden and in the house

On trees

Lindens, Norway and Japanese maples, sassafras, purple-leaf plum, crabapples and elms are among the favourites named by Kentucky and Purdue. The beetles usually feed in groups, starting at the top of a plant and working downward, and prefer plants in direct sun. Young or recently planted trees are the ones most worth netting or protecting, since a small canopy can be stripped quickly.

In the garden

Roses, grapes, raspberries and green beans take much of the damage in vegetable and flower beds. Kentucky reports that many common trees and shrubs are rarely attacked; Purdue lists red maple, ash, holly and most evergreens among resistant choices. Our garden pest control guide explains why spraying vegetables carries its own label limits.

In the house

Japanese beetles do not live or breed indoors. Eggs are laid in turf soil and the grubs feed on roots, so a beetle in the house has flown in through an open door or torn screen, or been carried in on plants. Remove it and repair the screen; no indoor treatment is needed. Other beetles that turn up indoors in numbers, such as Asian lady beetles in autumn, are a different problem.

Our data: the beetle is moving west, unevenly

USDA APHIS records that by 1972 the beetle had been reported in 22 states east of the Mississippi plus Arkansas, Iowa and Missouri, and that regulation and monitoring have so far kept it from establishing in most of the West. Colorado State reports permanent, reproducing populations along the Front Range and in Mesa County. To remove the effect of iNaturalist’s own growth, we express each year as records per 10,000 observations of anything in that state.

• Colorado: 2 records in 2015 (1.9 per 10,000) rising to 514 in 2025 (17.83 per 10,000), a steady climb that fits an established, spreading population.
• Kansas: no records in 2015, 142 in 2025 (18.24 per 10,000).
• Nebraska: rose sharply to 59.85 per 10,000 in 2019, then settled to 17.79 by 2025.
• Washington and Oregon: almost nothing. Washington has 2 research-grade records, both in 2021.

That Washington figure is a useful warning about what citizen records can and cannot show. In the same year, 2021, the Washington State Department of Agriculture trapped more than 24,000 Japanese beetles in and around Grandview, as part of an eradication programme that treats lawns and mass-traps adults. Records show where people photograph beetles, not how many there are. In the West, if you think you have seen one, report it to your state department of agriculture rather than just managing it.

Frequently asked questions

Can you permanently get rid of Japanese beetles?

Not once they are established in your area. USDA APHIS states there are no quick fixes that rid homeowners of the beetle after it becomes established, because adults fly in from surrounding properties. What works is reducing damage each season: daily handpicking, netting valued plants, choosing less-preferred plants, and treating the lawn only when a grub count calls for it. Eradication is possible only for small, new, isolated populations, through state-run programmes.

What do Japanese beetles hate the most?

No scent or spray reliably repels them. Kentucky entomologists class garlic, hot pepper and orange peel extracts, insecticidal soap and companion planting as generally ineffective. What the beetles avoid is certain plants: Purdue lists red maple, ash, holly and most evergreens among resistant species, and Kentucky notes many common trees and shrubs are rarely attacked. Neem products deter feeding for only about three to four days.

Why do I suddenly have Japanese beetles?

Adults are strong fliers and can reach new areas from several miles away. Once a few feed on a plant, odours from the damaged leaves attract more, so numbers build quickly. Lawn moisture also matters: females lay eggs in moist turf, and irrigated lawns in dry summers can support large grub populations. In parts of Kansas, Nebraska and Colorado, the beetle is also still expanding its range.

What month do Japanese beetles go away?

In most areas the adults are largely gone by late August or early September. Kentucky describes a 4 to 6 week peak beginning in late June, after which beetles gradually die off, and Colorado State says a few persist into September. Our analysis of iNaturalist records puts the peak in July, with records falling to a quarter of that peak by September. The grubs remain in the lawn until the following summer.

Sources

• University of Kentucky Entomology, ENTFACT-451, Japanese Beetles in the Urban Landscape (revised 2026).
• USDA APHIS, Managing the Japanese Beetle: A Homeowner’s Handbook (2015 edition).
• Colorado State University Extension, Fact Sheet 5.601, Japanese Beetle.
• UF/IFAS Featured Creatures, EENY350, Japanese Beetle, Popillia japonica Newman (revised 2019).
• Purdue University Extension, E-75, Japanese Beetle.
• Gordon, F.C. and Potter, D.A., Efficiency of Japanese beetle traps in reducing defoliation of plants in the urban landscape and effect on larval density in turf, Journal of Economic Entomology 78 (1985); and 1986 follow-up on single and multiple trap arrangements.
• Redmond, C.T. and Potter, D.A., Lack of efficacy of in vivo and putatively in vitro produced Bacillus popilliae against field populations of Japanese beetle grubs in Kentucky, Journal of Economic Entomology 88 (1995).
• Wawrzynski, R.P. and Ascerno, M.E., Mass trapping for Japanese beetle suppression in isolated areas, Journal of Arboriculture 24(6) (1998).
• Washington State Department of Agriculture, Japanese Beetle Eradication 2023 Wrap-Up.
• The Pest Control Brief analysis of iNaturalist research-grade records, pulled October 2026.