White Lawn Grubs
A complete guide to identifying and getting rid of damaging lawn grubs
Everything you need to know about white lawn grubs
By the team at DIY Gardening
Are you experiencing an issue with white lawn grubs?
These pests can devour your lawn’s roots, munch on the top growth and to rub salt into the wound, they attract badgers, foxes and large birds that tear up the lawn in a frantic attempt to feast on the grubs.
Even a small, localised infestation can result in noticeable lawn issues such as:
- Browning or yellowing of the grass.
- Bare patches.
- The grass pulling away easily.
- Little or no growth.
- Susceptibility to disease and other pests.
Neglected lawns with severe infestations can look horrid with dead and dying grass leading to moss and weeds taking hold.
Chafer grubs are a real lawn wrecker, but with a little effort, you can get rid of them.
Unfortunately, commercially available insecticides won’t work on lawn grubs, but there are solutions for gardeners.
Because lawn grubs are only active at certain times of the year, the treatment must be applied ar specific times, or it won’t work.
The good news is that in most cases you will be able to control the numbers of lawn grubs or even completely eradicate them, and you shouldn’t need to dig up the entire lawn.
First Identify the Lawn Grubs
In the UK several different species of grub are known to damage lawns, but the two most common ones are chafer grubs and leatherjackets.
The first step for any gardener is to identify which grub has infested their garden as the treatments for each species is different.
Leatherjackets are dark in colour, relatively straight and cylindrical and usually over 2cm in size. They don’t have a distinctive head or legs.
Here is what a leatherjacket looks like:
If your lawn grubs look like this, then go and check out our guide to getting rid of and preventing leatherjackets.
The other type of lawn grub that is often found in the UK is the chafer grub, and the remainder of this guide will cover information and treatment suggestions for this grub.
This grub is just as destructive as leatherjackets but is distinctive and easy to identify:
- Is a white or creamy white coloured lawn grub.
- Has distinctive legs at the front of the body.
- Often curls into a “C” shape.
- Has a brown head, just in front of the legs.
This is what chafer grubs look like:
The Best Time to Treat Chafer Grubs
Chafer grubs aren’t active all year so you’ll need to apply any treatment or removal technique at specific times.
Here’s a brief explanation of the chafer lifecycle:
- August – The chafer beetle lays eggs just below the grass which hatch into chafer grubs and start feeding.
- September to October – The white chafer grubs feed on lawn roots and some top growth.
- Mid-November to Mid-March – As the temperature cools, the grubs burrow deeper into the soil and are less active.
- Mid-March to May – The grubs feed on more roots and top growth as the soil temperature rises.
- May to June – The chafer grub turns into a pupa.
- Late May to June to early August – The chafer beetle is born and lays eggs, usually in August.
- The lifecycle is complete and now starts all over again.
As you can see, the white chafer grubs are most active from August to October and in the spring from mid-March to May.
The best time to apply any treatment is when the grubs are young and actively feeding, which is in late August and September, possibly into early October if the soil temperature is still warm.
You can also apply the treatment in the springtime, but the soil temperature must be above 12°c. As the grubs will have hardened over winter, the success rate for Spring applications is below that of Autumn treatments.
Image from Nemasys Chafer Control.
How to Kill White Lawn Chafer Grubs
We’ve got several suggestions for you to try, timing is critical here, and they won’t work in the middle of the summer or winter:
1) Use Nematodes
Nematodes are tiny parasitic worms that attack the grubs and kill them from the inside.
As a bonus, nematodes will lay eggs inside the grubs which will hatch and release more nematodes; these will seek out more grubs and kill them.
One small pack contains millions of nematodes, and they are 100% safe for pets, humans, children and plants.
Nematodes won’t harm regular garden worms or insects as they only target the grubs, and they are suitable for organic gardening.
Nematodes are by far the best way to treat chafer grub infestations, but there are some limitations:
- They must be applied at the correct time of year when the grubs are active, not in the middle of summer or winter.
- You’ll need to water the lawn frequently for at least two weeks; otherwise, the nematodes will die.
- Nematodes are perishable so you must use them as soon as they are delivered or store them in the fridge for no more than a few days.
- Repeat applications are almost certainly required.
2) The Tarp Method
This is an excellent method for small and medium-sized gardens when the grubs are active and devouring the roots (see the lifecycle info above), I’ve seen the tarp method successfully deployed on golf courses in the past.
First, you need to buy a dark plastic cover, such as a tarpaulin, the size will depend on how big your garden is but you can do this in stages if you have a vast lawn.
Pick a warm yet cloudy day and water the grass well, so it’s saturated, you don’t want the water to evaporate so avoid hot sunny days.
Now lay the sheet over the grass and secure it at the edges with pegs or heavy objects such as bricks or plant pots.
Leave the tarp on overnight and lift it early in the morning. The warm, dark and moist environment under the tarp will encourage the grubs to the surface where they can be either picked up or swept into a container.
You’ll need to repeat this process several times and for large lawns, move the tarp around the garden in stages.
The tarp method is a great way to reduce chafer grub numbers and works very well when they are active.
3) Encourage Natural Predators
White lawn grubs are a delicacy in many countries but don’t worry; we aren’t suggesting you dig them up and cook them for dinner!
Birds love these juicy garden pests, and if you can encourage more of them to your garden, they’ll be able to pick off some of the grubs.
Chafer grubs often surface during the nighttime and early morning when the temperature isn’t too cold. By placing birdbaths and feeding stations around your garden with plenty of bird food, you should be about to attract some early morning birds to feast on the chafers.
You should avoid throwing seeds directly onto the grass as this will encourage badgers and foxes to visit, and they will tear up the lawn as they search for the grubs.
Some lawn damage from birds is to be expected, but it can usually be repaired easily with overseeding and a little TLC.
Check out our guide to the best squirrel proof bird feeders if you want to encourage more birds to visit your garden.
4) Improve the Quality of the Lawn
Chafer grubs can be found in any lawn, but they prefer plenty of thatch to feed on and are more likely to flourish in sparse lawns that provide plenty of space for them to burrow into the soil.
Lawns that are regularly dethatched, fertilised and generally well-tended are often denser and therefore less appealing to the grubs.
We recommend regular raking and dethatching along with a fertiliser regimen to keep the lawn as dense as possible.
If your lawn is very mossy, you should take steps to remove the moss; lawn grubs seem to thrive in mossy lawns.
Excessive watering will only encourage the grubs to be more active so until the infestation is under control, we suggest you dial back any watering to the minimum.
Our lawn care guide is the best place to learn how to create the perfect lawn and is a great place to start.
5) Pheromone Lure and Traps (for chafer beetles)
Note: this is a beetle trap and not a grub trap.
This method is a long shot and untested by us here at DIY Gardening although we have heard of mixed results from gardeners with lawn chafer infestations.
This device contains two parts; a trap and a lure which includes a powerful chafer beetle pheromone.
The beetles are attracted to the pheromone where they meet their demise by getting caught in the trap.
While the trap is reusable, the pheromone can only be used once.
As with other products, timing is critical, and this trap and lure only works on beetles and not grubs, so it must be used before the beetles lay their eggs.
The best time to use this lure is in late May or early June as the pheromone is only active for around six weeks.
While this product won’t kill all the beetles, but even getting rid of a few will have a knock-on effect as they won’t be able to lay eggs.
We feel that beetle lures and traps should be a last option, worth try for sure but it won’t be as effective as nematodes or the tarp method.
White lawn grubs, also known as chafer grubs, are one of the most destructive lawn pests in the UK. See incredible photos of the damage they can cause here. They can completely destroy a lawn if left unchallenged as their numbers increase each year exponentially.
Warm winter weather can make the infestation worse, but no matter how severe the problem, there are solutions.
The tarp method is a great way to surface the grubs and nematodes, if deployed at the correct time, can significantly reduce the population of grubs in the lawn.
As with most perennial pests such as white grubs and leatherjackets, the sooner you act, the better.
It’s doubtful that white lawn grubs will go away of their own accord, certainly not before they’ve devoured your lawn!
We hope you found this guide helpful.
Danny Woodley at DIYGardening.
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