Order: Coleoptera (Beetles)
Family: Scarabaeidae (Scarab Beetles)
Species: Rhizotrogus majalis

The European chafer was introduced in the 1920’s on the East Coast if the United States. The States that are currently infested with European Chafer include the North Eastern US extending to Michigan. This pest is a serious problem in turf and cereal crops in the Eastern U.S. and Europe.

Image Source - GrowerCentral.com

Adult beetles emerge in mid-June and will be present through July and possibly August in Washington. In this time period, during the evening, the beetles swarm at dusk. These “swarms” can be rather noisy, sounding like buzzing bees. The beetles mate as darkness sets in and females will seek ovipositional sites in the soil soon after mating. Eggs are laid singly inside earthen cells. A female will lay 20-30 eggs. Larvae will hatch from the eggs two weeks later and begin to feed on plant roots. The larvae are “C”-shaped, about ¾ inch long when mature, white with a darker distinct head capsule. They appear much like root weevil larvae but scarabs have three pairs of visible legs and grow much larger. Chafers spend the winter as larvae and will pupate in May the following year, emerging as adults 2-3 weeks later in June.

Larvae are the damaging stage of this pest. Generally, European chafers prefer to feed on cereal plants like turf and wheat. Larvae can feed on just about anything and have been found damaging the fine roots of broadleaf plants and conifers. In turf, larvae feed in the root zone up to the root crowns of turf grass. Heavy infestations cause browning and death of turf, especially as drier months begin. Secondary pests, such as raccoons and skunks will peel back turf to feed on the grubs causing significant damage to lawns.

 
Image Source - BC Ministry of Agriculture & Lands

Monitoring for white grubs is very similar to that for crane fly. The threshold for white grubs is dependant on the health of the turf. Generally, 5 to 10 grubs per square foot warrant management tactics. Monitoring adult flight can be fairly obvious because of their swarming behavior and the noise they make.

Managing the European Chafer will not be easy. Reports across the country have alluded that this pest tolerates many insecticides and the currently recommended ones are unsavory for birds or pollinators.

This is why surveying for potential introductions of this pest is very important and crucial for management of the European Chafer.

Many thanks to Todd Murray for some of the information contained in this article.