Chafer Grubs in lawns. The larvae - grub - of the chafer beetle can do considerable damage to lawns, as it lives its life under the turf - eating away at the grass roots.
The Chafer grub feed on the roots of the lawn turf during spring and summer. Whilst not as much of a problem as Leatherjackets, they can still leave the lawn with several dead patches.
Small brown patches of turf, which can easily be pulled away are the tell-tale signs of the chafer grubs in lawns, together with birds pecking down into the lawn. Starlings, crows and magpies in the main, together with a few animals such as foxes and moles which scratch into the lawn in search of this juicy morsel!
In light soil areas, the chafer grubs can be controlled by rolling the lawn in spring - this crushes them. However, this should not be carried out in heavy soil areas. This is quite effective, and a heavy roller is not necessary. Light soil lawns where 'roller' mowers are used, seem not to have problems with Chafer Grubs!
Nemasys - is a biological control - will kill the grubs, but they can also be killed off with Provado Lawn pest treatment which will be avaiable from any good garden centre.
More damage can often be done by predators scratching at the lawn to find the Chafer Beetle Grubs than by the grub itself. However, the yellow spots in the lawn are unsightly in well maintained lawns. Isolated spots can be dug up with a daisy grubber in order to find the grubs, then carefully eased back after disposing of the grub - which is normally a few inches under the turf.
The Chafer grub in the image is well advanced. Younger grubs will not have the legs formed as in this image.
Whilst it is normally the larvae or grub of the Chafer Beetle that does the damage to turf roots, the adult beetle also lives in the ground for much of its adult life. Not too difficult, for the Chafer Beetle adult normally lives as a beetle for around two weeks only! The Chafer Beetle grub then, lives for the rest of the life cycle in various stages of development - all taking place under your lawn.
It is easily recognised with its characteristic curled habit. In typical insect form, it has three pairs of legs - normally visible in all but the youngest stages of development. It is creamy white, all but its light brown helmet of a head. The plump beetle make a good feast for birds as above.
The bad news is, that the Chafer Beetle Grub lives under your lawn for up to twelve months, before emerging as an adult beetle for just a couple of weeks. Does its mating and then back underground. It mates by flying into surrounding trees. Does the job, back to earth, lays its eggs and then dies. All in the spell of a couple of weeks.
We are left with its offspring to deal with for up to a year! To make matters worse, it feeds for most of that year on the roots of grasses - your lawn! The only respite from its feeding regime, is in the coldest of winters. If it is not freezing, it will eat.
Damage is rarely noticed until the spring, when the grasses that used to have roots, soon wither and die as the weather warms up. It is only in severe infestations of the Chafer Grubs that the damage is ever anything worse than a few small patches of browned grass. However, if a warm humid period coincides with the adults mating time, then a good crop of young Chafer Grubs will soon make the lawn look unsightly.
Not surprisingly, the beetle are rarely seen, for they normally fly at night to their mating perches up in trees. Sometimes there are enough of them to create an unpleasant looking swarm. They do not bite humans as far as we are aware. They are essentially vegetarians!
Leatherjackets also tend to leave the same type of brown patches - but normally visible in the late summer.
Other causes of brown patches on the lawn....