Lawn: Chafer Grubs

How do I know if I have Chafer Grubs?
The first “tell” if your lawn has Chafer Grubs, or for that matter, Leatherjackets is usually secondary damage from prey. Chafer grubs eat the roots of the grass plant. This cuts off the plant’s food and water supplies but more importantly, it cuts off its ability to anchor itself to the soil. Thus, when foxes, badgers, or birds come to prey on the grubs they can just scratch the lawn back and help themselves. If secondary damage is not visible you may be able to see a random browning of the grass. Pick several browning areas and try and pull back the turf. If it is well anchored you can rule out these pests.

If you see a sight like this, try to pull back the edges of the lawn. They will likely roll up like a piece of turf. And when you do, this is what will meet you.

It is quite normal to have the odd chafer grub in your lawn or even dozens of them if it is a large lawn, but in these numbers and density seen above the lawn is likely to be infested.

What are Chafer Grubs? What are Leatherjackets?
We group these larvae together as they behave in much the same way but usually at different times of the year. They are the larval stages of the Chafer Beetle and the Crane fly respectively. The adult forms both lay their eggs in the soil, which hatch as larvae and subsequently eat the roots of the grass plant, before emerging as another adult form. This is a somewhat simplified explanation of their lifecycle, to which there are many stages! The larvae will move up and down the soil profile depending on temperature.

How do I get rid of Chafer Grubs?
Chemical control is not available for either of these lawn pests, but biological control is available in the form of nematodes. These are microscopic worms that are sprayed onto the soil. They move through the soil with the aid of water. They find their host which must be at a specific stage in the life cycle, enter it and eat it from the inside. These nematodes are not a foolproof answer. Timing is critical. Lawns should be aerated prior to application to help the nematodes get close to their host and plenty of water must be available to help them travel. If all this is right, you can expect about a 50% kill rate. For this reason, LawnsOne does not offer this as a service.

This is how LawnsOne would recommend dealing with Chafer Grubs and LeatherJackets. Firstly, net the area concerned. This should prevent further (if there is any) secondary damage from predators. Water the lawn profusely and apply an autumn fertiliser. Encouraging the grass plant to root again. We then advise the customer applies nematodes at the correct time (we can provide supplier details for this). We can of course aerate the lawn. The nematodes will need re-applying for up to four years to ensure the infestation is controlled.

If the damage is too far gone your LawnsOne professional will strip the turf and dispose of it, exposing the grubs to predators. The soil is turned a number of times over the course of a few weeks to expose more of the grubs each time. A nematode solution is then applied and the area re-turfed. LawnsOne has had complete success using this process. It does take time, but it is 100% biological, organic, and successful.

Key points to remember
Secondary predatory damage is often worse than the primary damage.
Net the affected area immediately to prevent secondary damage.
Water and feed the lawn, with an autumn fertiliser.