Rose chafer Macrodactylus subspinosus
IDENTIFICATION — Rose chafers have a deceptive name – they feed on a wide variety of plants, not just roses. These tan beetles are about ½ in. long and have long, orange legs. Adult beetles emerge suddenly in May or June, feed for about a month and then disappear again. The adults only live for a month, so their damage is limited.
Adult females lay eggs in late summer. The larvae hatch, feed on grass roots, and overwinter below the frost line. In spring, they pupate and emerge as adults. Rose chafers prefer sandy soils and are most often found in the northeast United States and eastern Canada.
DAMAGE — The larvae cause limited damage to grass roots. But hungry adults chew large, irregular holes in foliage, fruit and flowers (especially those with white petals). Rose chafers can be toxic when eaten by poultry and small birds.
CONTROL — Prevention is the best policy when it comes to rose chafer beetles. They won’t lay eggs in moist soil or shade. Beneficial nematodes applied to the lawn in spring or fall will kill rose chafer larvae and pupae in the soil. These nematodes are available at Gardens Alive! (www.gardensalive.com).
Small numbers of this pest aren’t too difficult to control. Handpick adult beetles and drop them in a bucket of soapy water or rubbing alcohol. Do this in early morning or at dusk, when beetles are more sluggish. Or make a trap by filling white buckets with an inch of soapy water and setting them near the plants. The beetles, attracted to the white color, will drown.
For large numbers of rose chafers, try organic pesticides like neem, insecticidal soap, rotenone and pyrethrum. Insecticides like carbaryl (Sevin®) and acephate (Orthene®) are also effective.