How to recognise it
The larvae live in soil and are white, c-shaped and up to 40mm in length with a brown head and three pairs of thoracic legs. The damage caused by the larvae appears as plants wilting and dying (similar to the symptoms of a vine weevil attack, although vine weevil larvae are without the thoracic legs).
The appearance of the adult varies by species:
Cockchafer – also known as the May bug the adults are up to 30mm long with red-brown wing cases, clubbed tips on the antennae and white triangular markings on the sides of the abdomen. Larvae are the largest of the chafer grubs, growing to 40mm length.
Garden chafer – these are up to 12mm long and the head and thorax are metallic blue-green with brown wing casings.
Summer chafer – also up to 12mm long, these are distinguishable from the garden chafer as they are entirely red-brown without the metallic blue-green colouring.
Brown chafer – adults are about 15mm long and entirely red-brown, common in well-wooded areas.
Rose chafer – up to 20mm in length these are bright metallic green and the adults are often found feeding on and around roses in June.
Welsh chafer – the smaller species, being only 11mm long, this has reddish-brown wing cases with a black head, thorax and legs.
Lifecycle
Females lay eggs in the soil near plants (ie to ensure a food source) in early summer. The larvae hatch a few weeks later and feed underground on roots, corms, tubers or rotting wood until they are ready to pupate (which can take between 1 and 5 years depending on the species). The pupa resides about 60cm down in the soil before emerging as a fully grown adult.
Why it’s a problem
The larvae feed on roots, corms, tubers and stems of plants including raspberries, strawberries, potatoes, lettuces, young trees and many herbaceous perennials. Lawns are also susceptible to attack. The affected plant will wilt and die when the main root is severed.
In lawns brown, withered areas appear during dry weather – lifting the turf usually reveals the larvae underneath. Further damage may be done to lawns by predators such as foxes, badgers, crows, magpies, starlings and jays ripping up the turf to feed on the larvae.
Adults can also damage plants by feeding on leaves, buds, flowers and fruits of apples, roses and some other plants.
Where you are likely to find it
Mainly in near plants in newly cultivated areas or under lawns.
How to deter it
Winter and spring digging can expose the underground pupae.
How to get rid of it
If a lawn is infested then heavy rolling in late spring can kill the pupae and emerging adults. Good maintenance of (eg watering and feeding) will give it a better chance of surviving any damage caused. Re-seeding in the spring may be necessary following a particularly severe attack.
A lawn treatment containing imidacloprid is available to control chafer beetles in grassed areas.
Biological control is available with the nematode Steinernema carpocapsae on moist, warm (min. 14˚C), light soils.
Is it good for anything?!
In breaking down organic matter they are making nutrients available to your plants. They also provide a good source of food for their predators, encouraging wildlife in your garden.
Other useful information
Beetles (Coleoptera) are the largest order of insects, with over 400,000 species identified to date.
