NC State Extension Publications

Description and Biology

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Oriental beetles, Anomala orientalis, are about ½ inch long and are oval in top view. They range in color from solid black to mottled black and brown, to almost completely unmarked pale brown. The eggs are small and spherical. Oriental beetle grubs are almost identical to those of Japanese beetles, that is, C-shaped white grubs that grow to almost ¾ inch long. However they can be distinguished by parallel rows of setae on the raster visible only with a hand lens. Adults begin to emerge mid June (shortly before Japanese beetles emerge) and may continue to emerge into September. They feed and mate after emergence. After mating, females burrow 2 to 4 inches into the soil and lay eggs. Females enter the soil several and lay several eggs each time. Females prefer well watered, but dryer sites are also infested. Eggs cannot develop in extremely dry soil. This beetle flies in the evening with peak activity between 7:00 and 11:00 PM with a maximum around 9:00. The majority of adult emergence takes place in July. By late July, grubs actively feed on soil organic matter and plant roots. Newly hatched grubs feed on fine rootlets of turfgrasses as well as dead organic matter. Grubs molt twice as they grow during the summer and are found in the top 2 inches of the soil profile. As soils cool in the fall, the grubs dig down further to spend the winter. As soils warm the following spring, the grubs ascend to feed for 4 or 5 weeks. Grubs then tunnel downward to pupate in a cell. Sometime later, a new generation of adult beetles emerges from the soil to continue their wheel of existence.

Oriental beetle

Oriental beetles are black, mottled or tan.

Oriental beetle eggs

Oriental beetle eggs are spherical.

Oriental beetle grubs

Oriental beetle grubs are typical white grubs.

Host Plants

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Adults can cause minor damage to most flowering plants, but are particularly attracted to daisies. roses, hollyhock, phlox, and petunias. Grubs sometimes cause seriously damage roots of annual and perennial grasses as well as fully grown nursery stock and even containerized plants.

Residential Recommendations

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Some biological suppression of oriental beetles is given by the spring typhia, Tiphia vernalis, a small, black wasp that digs down to oriental beetle grubs and lays its eggs on the grub. The spring typhia egg hatches and the wasp grub eventually consumes the oriental beetle grub. The spring typhia grub then spins a cocoon in which it spends the winter, pupates the following spring, and a new generation of wasps emerges later. Tiphiid wasps are harmless to humans unless one is handled carelessly or stepped on.

It is not a good idea to spray flowers to protect them from oriental beetles, Japanese beetles, or any other chewing pests as pollinators and butterflies are bound to suffer from the pesticide residue. Suspending a light bulb over a pan of soapy water each evening helps catch many oriental beetles as they fly about. Place the pan on the ground with the light bulb a few inches above it. To control oriental beetle grubs, apply an insecticide labeled for turf pest control in home landscapes. Fortunately, oriental beetles are not thought to be resistant to pesticides. The garden supply sections of most big box stores have several pesticides available.

Tiphia vernalis

Tiphia vernalis is a parasite of oriental beetles and Japanese beetles.

References

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For assistance with a specific problem, contact your local Cooperative Extension Center.

This Factsheet has not been peer reviewed.

Author

Professor Emeritus
Entomology and Plant Pathology

Publication date: Aug. 2, 2016
Revised: Oct. 9, 2019

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