Rose chafer
A slender tan scarab beetle, 5/16 to 1/2 inch long, with long, spiny, reddish-brown legs. The adults emerge in late May and June, feed for three to four weeks, and chew large ragged holes in roses, peonies and other flowers. They also skeletonise the leaves of grapes, raspberries, fruit trees and birch. The grubs live in sandy ground under grass and weeds and do not damage lawns. None of the extension guides we read recommends a beneficial insect or microbial against it. Pick the beetles off into soapy water or cover the plants during the flight, and keep chickens away from them: the beetles contain a toxin that can kill birds.
Adult Macrodactylus subspinosus feeding on a rose bloom. Photo: pending.
Identification
Adults are 5/16 to almost 1/2 inch (8–13 mm) long, slender and tan to pale green, with conspicuously long, spiny legs that are reddish-brown or orange. Their short antennae end in a club of flat, plate-like segments, as in other scarabs. In flight a rose chafer can look like a wasp. Beetles live for about three weeks.
It is often confused with the Japanese beetle, which also feeds on roses and grapes. The Japanese beetle has a metallic green head and thorax with copper-brown wing covers (Minnesota Extension); the rose chafer is slender, pale green to tan, with long reddish-brown or orange legs. In the Northeast, rose chafers start emerging around the end of May or early June, a few weeks before Japanese beetles. The grubs are C-shaped white grubs with brown heads, about 3/4 inch long when grown, and are rarely seen.
Easily confused with
- Japanese beetleAlso a pestFeeds on the same roses and grapes, but has a metallic green head and thorax with copper-brown wing covers. A rose chafer is slender and pale green to tan, with long, spiny, reddish-brown or orange legs.
- WaspsBeneficial — leave itIn flight a rose chafer can look like a wasp. At rest it is a beetle: tan wing covers over the body and long, spiny, reddish-brown legs.
Damage symptoms
The adults do all the damage, and they do it quickly because they arrive in numbers. They prefer flowers, especially roses and peonies, and chew large, irregular holes in the petals. On leaves they eat the tissue between the large veins, leaving a skeleton. Grapes, raspberries and strawberries are damaged, as are the leaves of apple, cherry and birch. Plants on or near sandy ground are hit hardest, because that is where the grubs develop.
- Large, ragged holes in rose, peony and other blooms
- Leaves skeletonised between the veins
- Clusters of tan, long-legged beetles in open flowers
- Damaged grapes, raspberries and strawberries
Lifecycle & degree days
There is one generation a year. Adults come out of the ground in late May and early June and feed for three to four weeks, generally until late June. They mate soon after emerging, and the females lay eggs in the soil, mostly in sandy soil, then die. The eggs hatch two to three weeks later, and the grubs feed on the roots of grasses and weeds. They spend the winter below the frost line and pupate the following spring. Adults are strong fliers, so beetles from surrounding land keep arriving through the flight.
- Adult flight
- Late May to late June, 3–4 weeks
- Adult life
- About 3 weeks
- Egg hatch
- 2–3 weeks after laying
- Generations / yr
- 1
- Overwinters
- Grubs, below the frost line
Host crops
The adults feed on a wide range of flowers, trees and shrubs. Roses and peonies are the classic garden hosts. Among fruit, Minnesota and Maine name grapes, raspberries, strawberries, blueberries, cherries and peaches, and Maine adds corn, beans and peppers among vegetables. Minnesota also lists rose, grape, apple, cherry and birch among the plants whose leaves are skeletonised. The grubs feed on the roots of grasses and non-crop plants and do not damage lawns or landscape plants.
Monitoring & action thresholds
None of the extension sources we read gives a number for gardens. Minnesota Extension's guidance is to hand-pick when numbers are small and consider a garden pesticide when large numbers are present, knowing it may need repeating because more beetles fly in.
Start checking roses, peonies and grapes in late May, especially if you have had rose chafers before or garden on sandy soil. Check often through June, because new beetles keep flying in from surrounding areas.
Biological control
No biological control is recommended for rose chafer in the extension sources we read (Minnesota, Maine), and a PubMed search found no field trial of a commercial beneficial against it. Grub nematodes and milky spore are sold for lawn grubs, but we found no trial of either against this species. Rose chafer grubs live under grass and weeds in sandy ground and do not damage lawns, and treating a lawn does not stop adults flying in from elsewhere. Do not try to use poultry either: the beetles contain a toxin that acts on the heart, and both extension services warn that they can kill chickens, other birds and small animals that eat them.
Cultural controls
The flight lasts only three or four weeks, so protecting the plants through June is the whole job.
- Hand-pick beetles into a pail of soapy water, and check again often — more fly in
- Cover prized plants with cheesecloth or floating row cover as the beetles appear, and remove it once feeding stops after June
- Protect individual show blooms with bags, a Cornell rose IPM tip passed on by Maine Extension
- Keep chickens and other poultry away from the beetles; do not feed collected beetles to them
Chemical, last resort
- CarbarylREI 12 h
- PermethrinREI 12 h
- EsfenvalerateREI 12 h
Rating: the effect on this pest's natural enemies if a spray hits them or they feed on treated plants. REI is the re-entry interval on farm and greenhouse labels; home labels usually give none, so follow the label.
Sources
University of Minnesota Extension, Rose chafers (Hahn, rev. 2026)
University of Maine Cooperative Extension, Rose Chafer (Home and Garden IPM)
University of Minnesota Extension, Japanese beetles in yards and gardens
UC IPM Pest Management Guidelines: Asparagus; Cole Crops — Flea Beetles (REIs)
Page status
Drafted from the sources below, then checked claim by claim against those sources on 23 September 2026.
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