Warning signs checklist
- Yellow or brown patches that appear suddenly in late summer or early autumn
- Turf that lifts away from the soil like loose carpet when you pull it
- Spongy, soft areas underfoot where the grass roots have gone
- Crows, jackdaws, magpies or foxes digging systematically at the same spots
- Crane flies (daddy-long-legs) flying in large numbers in late August to September
If you have three or more of these, read on. If you just have a couple of yellow patches, check our bare patches guide first, as there are several possible causes.
Both chafer grubs and leatherjackets are soil-dwelling larvae that feed on grass roots just below the surface. The grass looks fine from above until the roots are largely gone, then it dies and the turf separates from the soil. The damage can be dramatic and fast, particularly in late summer when larvae are most active.
We see this in gardens across Sandwich, Deal, Worth, Ash and Eastry every year, usually reported to us in August and September when people come back from holiday to find a third of the lawn looking like it has given up. Kent's mild winters mean larvae survive in greater numbers from one year to the next than they do further north, so the problem can be persistent if left untreated.
The Lawn Master team, which trains professional greenkeepers across the UK, produced a useful overview of both pests, including what they look like in the soil: Lawn Pest Control: Chafer Grubs and Leatherjackets (LawnmasterTV, YouTube). It is worth a few minutes if you want to confirm what you are looking at.
Before you start: safety
- Wear gloves when handling soil and when mixing nematode solutions.
- Wash hands thoroughly after digging in areas with larvae.
- Keep children and pets off the treated area for at least 24 hours after applying nematodes, and until the lawn surface is dry.
- Do not use chemical insecticides on lawns unless specifically licensed for amateur use on turf, as most are withdrawn from sale and the remaining options carry restrictions.
Step 1: Tell the two pests apart
Lift a section of affected turf in the damaged area and look at the top 5 to 10 cm of soil. You are looking for larvae.
- Chafer grubs are white to creamy-white, C-shaped, 15 to 30 mm long, with a brown or orange head and three pairs of small legs clustered near the head end. They curl up when disturbed. The most common species in Kent gardens is the garden chafer.
- Leatherjackets are cylindrical, grey-brown and legless, up to 30 mm long, with a tough leathery skin (hence the name). They do not curl up. They are the larvae of crane flies, which lay eggs in lawn turf in late August and September.
It matters which one you have because the nematode species used to treat them are different. If you find both in the same lawn (not unusual), you will need to treat for both.
Step 2: Judge the severity
Count how many larvae you find in a roughly 30 cm by 30 cm section of soil. Fewer than five per sample is a low-level population that may not need treatment. Six or more per sample, or a lawn where the turf peels back in large sections, warrants treatment. If you are finding 20 or more per sample, the damage will be severe and you will likely need to reseed after treatment as well.
Step 3: Apply nematodes at the right time
Biological nematode treatment is the most effective option available to home gardeners. Nematodes are microscopic roundworms that enter the larvae, release a bacterium that kills them, and then multiply in the dead host. They are non-toxic to people, pets, birds and other garden wildlife.
The treatment windows matter:
- Leatherjackets: apply Steinernema feltiae nematodes in September to October, while larvae are still small and the soil temperature is above 5°C. Earlier (July-August) is generally too soon, as the eggs have not yet hatched.
- Chafer grubs: apply Heterorhabditis bacteriophora nematodes in August to September, while grubs are in their first or second year and still in the upper soil. Older, larger grubs go deeper and are harder to reach.
In both cases, the soil needs to be moist and the temperature above 12°C for the nematodes to move freely and work effectively. In East Kent, August and September usually offer these conditions, but in a very dry summer (such as the heatwave periods we have had) you may need to water the lawn thoroughly before and after applying.
Step 4: Apply correctly
Nematode products are supplied as a powder or gel you dissolve in water. Apply in the evening or on a cloudy day to avoid UV exposure killing the nematodes before they reach the soil. Remove any fine filter from your sprayer or watering can rose, as nematodes can get trapped. Water the lawn well beforehand, apply the nematode solution evenly, and water in again immediately after. Keep the soil moist for two to three weeks while the nematodes get to work. Results are usually visible within four to six weeks as the larvae die and bird activity drops off.
Step 5: Repair the damage
Once the infestation is under control, the areas where roots were destroyed will need reseeding. Our guide to fixing bare patches and our overseeding guide both cover the practical steps. For leatherjacket damage, early September is the ideal time to reseed once you have applied treatment; for chafer damage, you may get better results waiting until the following spring for a May overseed.
Stop and call us if
- Turf is lifting from the soil across a large area (more than a third of the lawn): the lawn may need professional renovation rather than patch treatment.
- You are unsure which pest you have and do not want to buy the wrong nematodes: a visit from us or a local lawn care professional gives you a confirmed diagnosis.
- The infestation has been present for two or more seasons without improvement: entrenched populations sometimes need a combined approach.
We can take a look
If you are not sure what you are dealing with, or the damage is beyond a patch job, get in touch. We cover Sandwich, Deal, Worth, Ash, Woodnesborough, Eastry and Sandwich Bay and can give you an honest assessment of what your lawn needs.