Chafer Beetles / Grubs

Chafer beetles and grubs present a potentially serious threat to the health of domestic lawns. The beetles are easily recognisable as being a flying insect, approximately 9mm (⅜”) in length, with brown wing cases and a brown or metallic green head.  

The adult chafer beetles emerge from the lawn, typically from late May to the middle of June, and after mating, lay their eggs on the turf within a couple of weeks or so. The eggs hatch into chafer grubs a few weeks later, and the grubs start to feed on grass roots until late autumn, before burrowing deep into the ground for the winter. Any initial damage may not be serious and could therefore perhaps go unnoticed, but damage will become obvious at the times when the grubs are reaching maturity, i.e., between autumn and early summer of the following year, when areas of the lawn may become yellowish. Having lain dormant during the winter, the grubs start to move back towards the surface in the spring, feeding on the grass roots as they go, before emerging as beetles, thereby starting the process again. 

The species most often found in lawns are the garden chafer, Phyllopertha horticola, and the welsh chafer, Hoplia philanthus; the latter is particularly found in sandy soils, and are therefore of particular concern for the areas of Nottinghamshire that sit on the Bunter sandstone.

The months of May and June (i.e., just prior to the eggs hatching out) are the ideal time to apply a chafer grub control, as the young grubs are more susceptible to the treatment..   

There is no doubt that the presence of chafer grubs presents a serious threat to a lawn. Like leatherjackets, the grubs eat the roots of the lawn and other plants, often with devastating results. The damage caused by the grubs eating the grass roots typically becomes obvious during late summer, when the areas of the turf may turn yellowish. The grass may also be found to be easily pulled up, because the roots have been so badly damaged that they can no longer ‘anchor’ the grass plant.

This damage is often exacerbated by the action of predators digging for the grubs. Birds are the chafer grub’s natural predator, particularly members of the crow family such as magpies and rooks, and hedgehogs, badgers and foxes will also dig up the lawn in order to feed on them. This activity can often cause more damage to the lawn than the grubs themselves.