Chafer grubs

Chafer grubs, the larval stage of the chafer beetle, can present challenges in grass areas as they feed themselves by consuming the roots of grass plants.

Adult Chafers are medium-sized reddish brown beetles about 13-15mm long.

It is the grub stage however that is most likely to be found in turf.  Damage is usually most evident in August and September. Early symptoms include gradual thinning, yellowing, and weakening of the grass stand followed by the appearance of scattered, irregular dead patches. As damage continues, the dead patches may increase in size, and apparently healthy turf areas may exhibit sudden wilting.  The turf may feel spongy as you walk over the infested area.

Adult Chafers emerge from the pupal cells in mid-June and continue mating until late July. The adults emerge at dusk and fly to nearby trees and shrubs where copulation begins. This copulation occurs in mass until dawn when adults return to the soil. Cool or rainy nights greatly reduce flight and mating activities, but eventually females dig into the soil and lay eggs. Each female lays 15-20 eggs in 2-5 days. They are usually laid in compacted soil, up to 150mm deep.

The eggs swell to approximately 2.0 x 2.7mm as they absorb moisture and hatch in about two weeks. The first instar (stage) are approximately 4mm long and may remain in the soil if surface moisture levels are low. however eventually the young larvae move to the surface and feed on plant roots. If food is sufficient, the first instar matures in three weeks and the second instars take a further four weeks to mature. The third instars which can grow to 17mm when fully grown feed for a period in the autumn before moving down into the soil for the winter. Pupation then occurs in mid-May 50-150mm into the soil.