Garden grubs can cause a number of different problems for those who grow plants. But what exactly are grubs? Which grubs might you encounter in a UK garden, how can you spot them, when and why are they a problem, and what might you do about them? I have put together a definitive garden grubs identification guide to help you find out just what is attacking your garden.
What Are Garden Grubs?
Before I go into detail about garden grubs identification, you may be wondering what garden grubs actually are. Well, garden grubs are the larval stage of a number of different insect species. Often, for example, they can be the larvae of chafer bugs, of which there are a number in the UK, of other beetle species, or of crane flies, for example.
Very occasionally, they might be the larvae of dangerous invasive species, such as the Japanese beetle and should be removed quickly to prevent their spread.
There are several different species – around 20 – of chafer bugs in the UK, and numerous other larvae that look very similar to these grubs, and the important thing to understand is that most do no harm at all in a garden.
What Do Garden Grubs Do?
Most of the grubs you find in a garden will not harm your plants or be a problem for you as a gardener in any way. In fact, most garden grubs are beneficial parts of the ecosystem – providing a food source for a number of different creatures and contributing to the local ecology.
However, there are a few species of grubs which do pose a risk, because they eat the roots of lawn grasses, or other plants. Grassy areas can also be damaged by wildlife that digs up the turf to find the grubs below. Sometimes, grubs may eat the roots of crop seedlings, or other plants in the ground or growing in pots or other containers.
Signs of Garden Grubs In The Garden
In order to understand whether problems with plants are due to grubs below the ground, it will often be necessary to dig a little below the ground or in the growing medium in a container to check around the roots and find the culprits themselves.
If chafer grubs, for example, have been eating roots in a lawn or grassy area, patches of the turf may become yellow and die back. You may also see telltale destruction where birds and other creatures have dug and delved to catch the grubs that have caused the problem.
Other plants whose roots have been attacked by these or other potentially problematic garden grubs may also wilt, turn yellow or brown, and die back.
Remember however that other things can also cause these problems and so it will often be very challenging to ascertain which garden grubs, if any, might be to blame.
Remember too that even when you spot grubs in the soil or growing medium in your garden, these are not necessarily of a type that will damage your plants.
Most garden grubs do not pose any threat to plants at all and in fact, are good to have around within the ecosystem to boost biodiversity and maintain a healthy natural balance within the space.
Garden Grubs Identification
Unfortunately, it can be very difficult and nigh-on impossible for the layperson to distinguish between the many different garden grubs they might unearth in their garden.
The grubs that can cause a problem can all look very similar to one another. And they can also look identical or near-identical to perfectly inert and even helpful species.
But let’s take a look at some of the species that can be garden pests, to help you work out which, if any of these, might be causing problems in your garden.
Here’s my garden grubs identification for the two most common grubs.
Chafer grubs are the larvae of a number of different chafer beetles. Most do not pose a threat for garden plants at all and are important parts of the garden ecosystem. However, some, such as the small garden chafer and Welsh chafer can eat grass roots, and the cockchafer and summer chafer will also very occasionally feed on plant roots.
Chafer grubs are white, chubby and C-shaped. They have light brown heads and three pairs of legs which are found close to their head ends. Many chafer grubs can reach around 1.8cm long, and large chafer grubs like the cockchafer and the summer chafer can grow up to around 3cm in length.
Remember, the vast majority of chafer grubs and chafer beetles are not detrimental to your plants, and in fact help you to manage an organic garden. One species, the rose chafer grub, is extremely helpful in a composting system, where they help break down organic matter.
Leatherjackets are the larvae of crane flies (Tipula subspecies), also known as daddy longlegs. There are a number of different crane flies that might be found in UK gardens.
The larvae are a greyish-brown, and have no clear head of legs visible. The size depends on the species but these too can grow to around 3cm in length. The name refers to the fact that these larvae have a tough and rather leather-like skin.
Leatherjackets can sometimes eat the roots of lawn grasses, leaving yellow or brown patches in a lawn. Occasionally, they can also become a problem in vegetable gardens, especially where the beds are newly created on what was once lawn. They can sometimes snip through seedling stems, causing their collapse.
However, most crane fly larvae do not pose any problem at all in a garden. In fact, many help in a garden by feeding on decaying vegetation and helping to cycle nutrients in the soil. And they are an important food source for a variety of beneficial wildlife.
Vine Weevils, raspberry beetle grubs and a number of other grubs are also sometimes considered to be garden pests. But like the above, the benefits they confer outweigh the problems when they are present in a garden.
How To Prevent Different Types of Grubs In Your Garden
If you’ve used my garden grubs identification and found that you’re struggling with one of these pests, there are several things you can do. The key thing to think about as an organic gardener is how you can work with nature rather than fighting it. Your attitude to garden grubs should be shaped by this idea and philosophy.
We should, when confronted with garden grubs that cause problems in our gardens, remember that these species, like all pests, are still important parts of the ecosystem. We should not try to prevent them at all, but rather should welcome them into our space.
And we should always keep in the front of our minds that most garden grubs are very much more beneficial than harmful.
Pick Them Off By Hand
When growing in containers or in raised beds, picking grubs up and removing them by hand can often be the best policy.
In an organic garden, of course, intervention of any kind is best avoided where possible and it is best to adopt a live and let live approach on the whole. But removing grubs from valued plants can prevent issues without depleting the biodiversity in your garden.
Go Earth-friendly With Beneficial Nematodes
As a last resort, where leatherjackets have become a problem, a biological control might be considered as the ‘nuclear option’. Since of course, in an organic garden, we never use synthetic pesticides at all.
For a serious leatherjacket problem, for example, pathogenic nematodes – Steinernema carpocapsae or Steinernema feltiae – might be used.
Remember, however, that mostly we can live and let live as these larvae do not usually pose a significant risk in a garden, and getting rid of them may do more harm than good.
Introduce Birds and Other Predatory Creatures Into Your Garden
By far the most important strategy for dealing with problematic garden grubs in an organic garden is boosting biodiversity as much as you possibly can. You goal in an organic garden should always be to encourage as many different creatures into your space as possible. This is the number one goal in organic pest control.
Remember, many garden grubs are a food source for numerous other creatures such as birds, badgers, foxes etc… and when we have plenty of predatory wildlife around, those grubs numbers should never be able to get out of control.
If you use my garden grubs identification guide, I’m sure that you’ll be free of those pests in no time.
Do you have any garden grubs identification tips? Leave your advice in the comments!
Elizabeth Waddington is a writer and green living consultant living in Scotland. Permaculture and sustainability are at the heart of everything she does, from designing gardens and farms around the world, to inspiring and facilitating positive change for small companies and individuals.
She also works on her own property, where she grows fruit and vegetables, keeps chickens and is working on the eco-renovation of an old stone barn.
To get in touch, visit https://ewspconsultancy.com.