Garden pest control - Cockchafer Grub (Description and control instructions)

Scientific Name: Melolontha melolontha
Other Names: Maybug, Rookworm

The fat white larval stage of the Cockchafer Beetle is quite destructive to cereal and other grass plant roots. They live in the soil for three or four years and are sometimes called Rookworms as Rooks are said to be particularly fond of adults and larvae. The adult beetles are up to 35mm long and can fly making them a little frightening as they buzz around, usually at dusk in May, but are harmless to humans. The adults are also destructive, feeding on flowers and foliage.

They are usually found in rough grazing or cereal crops and in new gardens. Turning over the soil exposes them to the birds. There is now a biological control which uses a parasitic nematode called Heterorhabditis megidis. It is applied to moist soil from late July to September when the grubs are most active close to the surface and the soil temperature is above 12C / 50°F. The nematodes invade the grubs over a period of 4 to 6 weeks and infect them with a bacteria which causes them to shrink and die. They are supplied under the trade name Nemasys Chafer Grub Killer and can be ordered by mail or online at any time, but will be delivered at the best time for use in August and early September. (Nematodes are also effective against Leatherjackets).

For chemical control Provado Lawn Grub Killer which contains Imidacloprid is a recent introduction for the treatment of Leatherjackets and Chafer Grubs.