Adult cockchafers eat leaves and flowers of a range of deciduous trees, plants and shrubs but do not tend to be serious pests in Britain. The larvae, on the other hand, can be serious pests of grasses and cereals, as they live in the soil feeding on roots. They can be serious pests in gardens, nurseries and pastures, causing brown patches of grass to appear. They also attack other garden plants and vegetables (4).
Adults appear in April or May. They feed for a time, and females become mature at 10 to 15 days after emergence. After mating, females lay around 20 eggs in soft soil. A large number of females die after egg-laying, but some return to feeding and may then go on to lay a second or even third batch of eggs (5). After 4-6 weeks the larvae hatches out. It takes 3-4 years for the larvae to become fully developed, and they burrow deeper into the soil each winter to hibernate (5).