Chafer grubs are the larvae of the Chafer Beetle. There are six species in the UK the Welsh Chafer, Summer Chafer, Brown Chafer, Cock Chafer, Garden Chafer and Rose Chafer. The grubs feed on the roots of grasses and other plants, their presence can be detected by the yellowing patches that it creates in turf. Chafer grubs can be found in the soil under the loose turf. They live within the soil for up to 3-4 years going through various ‘instars’ as they develop. Significant damage to turf can be done by predators such as starlings, rooks, crows, jackdaws, magpies, foxes and badgers that make the most of an abundant high protein feed lying just beneath the surface.
Chafer Grubs have stout white bodies curved in a C shape, light brown heads, with three pairs of legs and darker patches at the base of the abdomen. They are bigger than the adult beetles although their size varies according to species, 8-35mm; typically the Garden Chafer and Welsh Chafer are between 10mm and 15mm long. The head and thorax are metallic blue-green on the Garden Chafer and black on the Welsh Chafer.
The grubs eat the roots and damage and eventually kill the plant. The first symptoms are yellowing patches that eventually turn brown, particularly in dry weather. These areas are then pecked at or dug up by predators. In severe infestations the turf can be pulled back to reveal as many as 100 grubs per square metre.
Methods of Control
Biological control – The nematode Heterorhabditis megidis is commonly used as a biological control. The nematode penetrates the grub and infects them with a bacterium which is fatal to the grub. Best treated during August to early October.