Waiting too long could mean missing the window
Leatherjackets and chafer grubs are two of the most common culprits behind damaged and disappearing lawns, and autumn is a key time to tackle them. As the young grubs hatch into the warm, moist soil, they begin feeding on grass roots - and are at their most vulnerable while they are still close to the surface.
Gardeners often assume that once autumn arrives, there’s nothing more they can do about lawn pests until spring, but this is actually one of the most important times to treat. If conditions are right, there can still be time for two treatments before the end of the year, but gardeners need to act quickly before falling soil temperatures send the grubs deeper underground. Also before the ground becomes too cold for the nematodes to be effective.
So, what’s eating your lawn?
There are two main lawn pests to look out for: leatherjackets and chafer grubs. Leatherjackets are the grey, cigar-shaped larvae of crane flies - the familiar daddy longlegs. They hatch in late summer and early autumn and feed on grass roots, potentially leaving lawns with brown, thinning or bare patches. Chafer grubs are creamy-white, usually curled into a C-shape, with an orange- brown head and three pairs of legs near the head. Like leatherjackets, they feed on grass roots, while their presence can also attract birds, foxes and badgers that tear up the turf looking for them.
One of the easiest ways to check for either grub is to water a patch of affected lawn and cover it with black plastic sheeting for a few hours. The grubs may come to the surface, making them easier to identify without digging up the lawn.
So, what can you do about them?
If leatherjackets are the culprit, Leatherjacket Nematodes, which are watered into the lawn to seek out and kill the larvae. They should be applied when soil temperatures are above 10°C. For chafer grubs, the best treatment is Nemtodes for Chafer Bug, which is watered into the lawn to target the grubs. Soil temperatures need to be above 12°C for these nematodes to work effectively.
Depending on when the first treatment is applied and how long conditions remain suitable, you may be able to make two applications before the end of the year. This can be particularly useful because lawn pests do not all hatch at the same time, so a second application can target grubs that have emerged since the first treatment.
The important thing is to identify what you’re dealing with before choosing a treatment. Leatherjackets and chafer grubs look quite different, and there are different nematodes for each. You can see examples here.
If you’re able to treat twice, the second application gives you another opportunity to target newly emerged grubs. But don’t leave it too late - once soil temperatures drop, the grubs will move deeper into the soil and treatment becomes much more difficult.
Discover more about lawn pests
Not a pest eating your lawn? More advice here