In the garden: Grass/lawns
Throughout UK (although more common in the southern counties) and Europe
The cockchafer is about 2.5cm in length and is the largest species of chafer beetle in the UK. The adult beetles have reddish-brown wing cases and a black head with short fan-like antennae. Their bodies are hairy and have white cup-shaped markings down each side. Adult cockchafers are associated with deciduous woodland where they feed on tree leaves. Their larval grubs are creamy white in colour with brown heads. They live underground feeding on grass and plant roots. Adults fly at dusk during May-July and live for about a month. The grubs can live for over 2 years developing underground.
Adult cockchafers do not cause any significant damage to the deciduous trees that they feed on. The larval grubs often cause yellow patches to appear on lawns where they are feeding on the roots. This can result in dead patches. A number of plants can also be damaged in this way.
Adult cockchafers can be collected and removed from gardens when they are flying during May-July. They are often attracted to lights at dusk.
Areas of lawn where yellow patches are occurring can be lifted and inspected for chafer grubs, which can then be removed by hand. Commercially available entomopathogenic nematodes can also be used to water into the infested areas. These microscopic worms enter the grubs and cause a bacterial infection within which kills them.
Only control these chafers if the damage they cause is intolerable, otherwise it is advisable to let them be. In some areas cockchafers are becoming less common.