Guide to Common Garden Pests
A relatively small number of garden pests are responsible for most of the damage done to flower and food crops in UK gardens. Identify some of the usual suspects, along with their favoured foods, in our guide to common garden pests.
Those of a sensitive disposition may like to look away now …
Aphids (Greenfly, Blackfly)
Appearance: Aphids are extremely common and can significantly impact on plant growth. They have tiny soft pear-shaped bodies. There are hundreds of species, but the most commonly known can be grouped as greenfly or blackfly - although equally may be orange, brown or pink in colour. You may spot them clustered on the stem of soft shoots – look under leaves in particular – or may find a sticky substance on your plants that gives away aphids have been there sucking at the sap. Ants farm aphids and if you see ants running up and down the stems it is often a sign there are aphids.
Key Signs of Aphid Damage: Look for leaves that are curling, yellowing or misshapen. The presence of Honeydew (a clear, sticky substance, often accompanied by a black sooty coating) is another good indicator of aphids.
Favourite Plants to Consume: Aphids eat a huge variety of plants, both outdoor and in the greenhouse. They prefer soft, new shoots.
Ways to Tackle: A number of beneficial insects, including ladybirds, lacewing larvae and hoverflies, are natural predators of aphids so a good garden ecosystem will help with control. If there are not too many, you can also squash them. If your plant has a real infestation, gently shake the plant so the aphids fall off. They can also be rinsed off with a light solution of washing up liquid.
Appearance: These small white-winged insects, at just 1 or 2 mm in length, look very much like white moths as adults and are related to aphids. You may well spot them on the underside of leaves; they prefer younger, fresher leaves and they will fly in clusters when you disturb them. Their lifecycle is only three weeks long, which means an infestation can occur very rapidly.
Key Signs of Whitefly Damage: Whiteflies cause damage by sucking the sap from plants. This may not be immediately visible - you are more likely to spot the insects themselves - but a large infestation can lead to a black sooty 'mould' like appearance on leaves, which weakens plant growth. They are particularly prevalent in greenhouses.
Favourite Plants to Consume: They can be found on a wide range of plants, including azaleas, rhododendrons, honeysuckle, plus edibles including cabbages, tomatoes and cucumbers. As the name suggests they are most often a problem in the greenhouse.
Ways to Tackle: In greenhouses, you can catch adult whiteflies by hanging yellow sticky traps. You can also try companion planting as a form of deterrent; the strong smell of marigolds for example is a deterrent, so these are often grown next to vegetables or in a greenhouse.
Appearance: An unmissable, squashy-looking body plus small sensory tentacles on its head. Slugs move along on one muscular foot. They range in scale from surprisingly small to terrifyingly large; limax cinereoniger species can grow comfortably beyond 20 cm in length.
Key Signs of Slug Damage: Ragged leaves with holes in them, scalloped bites / nibbles at the edges of leaves. You are likely to be able to spot silvery slime traces near the damaged plant, or on it. Slugs attack at night so look for fresh damage first thing in the morning to confirm suspicions (or head into the garden in the evening armed with a torch – be sure not to go bare footed!). Most plant damage is done by small slugs and snails that go unnoticed, rather than the huge ones found on lawns.
Favourite Plants to Consume: These voracious molluscs consume almost anything, but particularly love tender leaves along with vegetable, fruit and salad crops.
Ways to Tackle: Encourage slugs’ natural enemies into your garden; slow worms if you are so lucky, hedgehogs, centipedes and (perhaps less practically) ducks. Some natural methods, like placing copper coins around plants, can also meet with success. Failing that, try organic control methods such as Slug Gone Wool Pellets.
Cabbage Moth Caterpillar
Appearance: By no means the only caterpillar species to wish to chomp on your vegetables, cabbage moth caterpillars are particularly challenging as they will happily make their way into the heart of the brassica. The caterpillars are distinguished in shades of yellow or browny green with no hair.
Key Signs of Cabbage Moth Caterpillar damage: Holes in the leaves of your brassicas. You may physically spot the caterpillars.
Favourite Plants to Consume: Cabbages and other brassicas – broccoli, sprouts
Ways to Tackle: Create a garden ecosystem that includes natural predators – birds in particular. You could also place a net over your brassicas as they grow. It is also possible to pick off the caterpillars and any eggs regularly by hand. Use marigolds as a companion plant that repels the cabbage white butterfly (don't plant marigolds too close though, as they can reduce the root growth of the cabbage).
Vine Weevil (adult and larvae)
Appearance: Otiorhyncus sulcatus, better known as black vine weevil, is a black-brown, moderately sized insect at around 1cm in length. It has a beetle-like appearance, with fused wings meaning they cannot fly, and orange hair tufts on their wing cases. Black vine weevil larvae are c-shaped, have no legs and are white - rather like maggots but with copper colour heads. The weevils are all female and a male has never been identified, so one can soon become a big problem!
Key Signs of Black Vine Weevil Damage: These highly destructive garden pests feed on leaves as adults and have a calling card of notch-shaped bites around the edges. The larvae feed on plant roots, causing the entire plant to die.
Favourite Plants to Consume: Black vine weevils are responsible for attacking a huge range of plants both in the garden and home, from perennials to shrubs and trees. They are particularly keen on plants in containers, such as heucheras and hostas.
Ways to Tackle: Options for control include picking adult weevils off of plants and removing larvae from the soil. A garden full of the animals that eat them will also help; in particular birds (including chickens), frogs and hedgehogs. For the larvae, the soil can be treated with a predatory nematode.
Appearance: Chafer grubs are the larvae of chafer beetles (cock chafer / Maybug, garden chafer or Welsh chafer) and live below ground in the soil. The cock chafer grub is found in beds and borders, feeding on plant roots. The other species feed on the roots of grasses and can wreak havoc on your lawn in particular. These fat white grubs have c-shaped bodies with light brown heads. Look for three sets of brown legs positioned near the head end to distinguish them from black vine weevil grubs.
Key Signs of Chafer Grub Damage: Wilting plants in borders or yellow patches of lawn and torn up turf where birds and other animals rummage for the grubs.
Favourite Plants to Consume: A variety of plants and grasses (lawns)
How to Tackle: One of the less common pests on this list, if found in beds and borders they can usually be removed with a trowel. For the lawn, water in the evening, cover with sheets to bring them to the surface then remove the cover at first light to create a feast for your garden birds.
Appearance: Mealybugs are tiny oval-shaped insects that have a white, powdery wax coating. There are several different species, many of which have what looks like legs coming from their sides and back end. In their earliest stage of life, it's entirely possible to mistake them for fungus and not recognise them as insects at all.
Key Signs of Mealy Bug Damage: Mealy bugs are sap-feeding insects. In the greenhouse, you will probably notice a white wax on less prominent parts of the plant under which are the insects or their eggs. Mealybugs excrete a sticky substance called honeydew, which may cause black sooty mould on leaves.
Favourite Plants to Consume: A wide range of plants grown in the greenhouse, including citrus plants and tomatoes; houseplants and especially cacti, succulents and orchids and less often outdoor plants including ceanothus, phormium and bamboo.
How to Tackle: Always inspect plants very carefully when you buy them for signs of a mealybug population, particularly if they are going to be growing in your greenhouse. Be careful to remove dead leaves and debris from your greenhouse as these could harbour eggs. Ladybirds are natural consumers of mealybugs; encouraging them into your greenhouse may be a natural deterrent. While plants can survive a small amount of mealybug damage, if the infestation is severe it may, unfortunately, be best to dispose of the plant. If an infected plant is in a pot, quarantine that plant to prevent spread. Multiple treatments will most likely be required to control this difficult pest.
Appearance: Adult lily beetles have a black head and legs combined with bright red wings. They grow to around 8mm long, so can be spotted relatively easily. Their eggs, which are laid on the underside of leaves are orangey-red. They emerge in mid-spring, having overwintered in sheltered spots such as among piles of leaves.
Key Signs of Lily Beetle Damage: These beetles make clearly visible holes in leaves and a severe infestation may eat through all foliage on a plant. If a plant has been attacked by lily beetles in the summer, because this can affect bulb development the plant may not flower at all the following year.
Favourite Plants to Consume: They are almost entirely found on lilies and fritillaries; these at least are the only plants eggs are laid on.
How to Tackle: Inspect your lilies and fritillaries regularly all through the growing season. Your plants will be able to survive a small amount of damage, so you may choose to ignore a minor amount. You can also remove beetles by hand. The best natural control method is predators including birds, frogs and wasps. There are insecticides available if other methods fail to keep an infestation under control.
Two-Spotted Spider Mite
Appearance: A tiny and common eight-legged insect, only around 0.4mm in length and oval in shape. The two spotted spider mite is orange-red to dark green in colour and has two or four very dark dorsal spots.
Key Signs of Two Spotted Spider Mite Damage: Attacked plants may develop a pale mottled appearance. The mites may be found under leaves, but may be difficult to say without the aid of a magnifying device. Leaves may fall off the plant and in really severe cases webbing may form over the plants, which can die under a heavy infestation.
Favourite Plants to Consume: This voracious mite will feed on a wide variety of plants, including greenhouse plants and houseplants. They are not usually a problem outside, but in very prolonged hot periods they will begin to appear outside too and attack plants in your beds and borders, including fuchsias and pelargoniums.
Ways to Tackle: Two spotted spider mites tend to be at their worst in hot dry summers, which helps them breed more quickly. You can spray affected plants with an insecticidal soap to control the worst of it. It is also particularly important with greenhouses to disinfect and clear thoroughly before the winter, to minimise any mites that may be trying to shelter there for the winter. Generally they attack plants that are under stress, so keeping plants well fed and watered enables them to better fend off the attack.
Appearance: These small insects are typically around 2-3mm long. The different species are mainly green or yellow in colour with mottled markings. They are thin with a body in the shape of a winged, narrow wedge.
Key Signs of Leaf Hopper Damage: A key sign of leafhoppers is the sight of them 'hopping' (as per their name) off plants when disturbed. They are present on the underside of the leaves and as the infestation grows the leaf will become pale in colour with mottled white on its upper side.
Favourite Plants to Consume: Leafhoppers feed on the sap of a wide variety of plants; some are specific to a single variety such as the rhododendron leafhopper and potato leafhopper. They are very often found on scented plants, such as herbs, lavander and nepeta. In the greenhouse, they are particularly keen on tomatoes, peppers and cucumbers and outdoors foxgloves, pelargoniums and nicotianas are just some of their favourite plants.
Ways to Tackle: Check your plants regularly for any signs of leafhoppers from their growing season in spring. A small amount of damage will not destroy plants and natural predators such as birds, ladybirds and wasps should do a good job at keeping them under control. If they are becoming a nuisance, insecticides are available for control.
Leaf Miner (inc Allium Leaf Miner)
Appearance: Leaf miners are small insects that lay eggs on a variety of garden plants. One of the more recent of these in the UK is the allium leaf miner, which was first spotted here in 2002. The flies of the species are small, around 3mm in length. Leaf miners lay eggs on plants in early to mid-spring once they awake from overwintering.
Key Signs of Leaf Miner Damage: These insects actually eat the inside of the leaf ('mining'), which leads to distinctive trail-shaped damage on foliage.
Favourite Plants to Consume: Depending on the insect they will be found on apples, holly, chrysanthemum, horse chestnut trees and alliums. The allium leaf miner actually consumes plants across the entire allium family, including leeks, onions, garlic, chives and shallots.
Ways to Tackle: There are limited ways to tackle this particular pest. Covering your plants with insect mesh – particularly in early spring and late autumn – is the best option. Crops, once affected, will not be able to be stored and will need to be safely destroyed.
Appearance: Scale insects are an ancient species with a diverse appearance. They can vary from 1-2mm to larger insects covered in wax. Mealybugs are technically a scale insect - one of the only species of scale insect that can move from the plant it inhabits. Female scale insects typically have soft bodies without legs, hidden beneath domed scales and they extrude a waxy substance. Males may look more like small flies.
Key Signs of Scale Insect Damage: Scale insects can cause serious damage. They can sometimes be identified by spotting scales or small bumps on stems and beneath leaves. Some leave a waxy substance on the top of leaves. The presence of Honeydew (a clear, sticky substance, often accompanied by a black sooty coating) is another good indicator of scale insects.
Favourite Plants to Consume: Scale insects suck the sap from a number of plants, including perennials, shrubs like camellias, fruit crops - especially citrus - and houseplants.
Ways to Tackle: If there is a small number, you may be able to pick them off with your nail. Birds are also a natural predator, so encourage them into your garden. Otherwise, treat with an organic spray, such as Resolva Natural Power Bug & Mildew Control. It may require multiple treatments as they are well protected by their waxy covering. Best results are usually achieved earlier in the season when the youngsters are still mobile (in their crawler stage).
Appearance: There are hundreds of different species of tortix moth. The caterpillars of the tortix moth develop from eggs in a matter of a few weeks and are small and green. The caterpillars roll themselves up in the leaves that they then feed on.
Key Signs of Tortix Moth Damage:
Favourite Plants to Consume: Tortix moths will go for your fruit plants and ornamental plants, both inside and outside. They can be particularly damaging in greenhouses.
Ways to Tackle: As totrix moths tend to overwinter before emerging in spring, keeping plants free of debris underneath them is a good way to prevent this. You can also squash caterpillars that you find rolled up in leaves.
Appearance: This variety of aphid is a black insect that sucks sap from woody stems, at the same time covering itself in a white waxy substance.
Key Signs of Woolly Aphid Damage: From spring into autumn look out for a fluffy white wax, that you may first mistake for fungal growth. Colonies on shoots will cause lumpy growths.
Favourite Plants to Consume: Woolly aphids are found on apple trees, pyracantha and Cotoneaster.
Ways to Tackle: Check any apple, pyracantha or Cotoneaster plants from spring onwards for any signs of woolly aphids. You can use a brush to scrub away the insects in small numbers. If left, then natural predators such as ladybirds, hoverfly larvae and lacewings will rapidly find and prey on the aphids. If the infestation becomes too large, organic controls are available.
Appearance: If all insects arguably have an alien appearance, earwigs are up there with the strangest. The black-brown bodies give way to frightening looking pincers on the back, although these are completely harmless. There are hundreds of different earwig species and, despite the folklore tales, they do not like to crawl into people’s ears. They will, however, create damage by chewing on the flowers and vegetables in your garden.
Key Signs of Earwig Damage: Look for ragged edges or holes on leaves and petals. Favourite Plants to Consume: A wide range of flowers, fruit and vegetables.
Ways to Tackle: Earwigs can bring as much benefit as damage to the garden, eating small insects – in particular fruit aphids. If the population is getting out of control, you could set simple traps by placing a flower pot filled with compost, grass or paper near the house and then emptying of any residing earwigs in the morning.
Appearance: First noted in private UK gardens as recently as 2011, box tree caterpillars can completely strip the foliage off of box plants. They are a particular problem in the South of England, though may inevitably spread further north. The caterpillars are green-yellow in colour with black heads, growing to 4cm in length.
Key Signs of Box Tree Caterpillar Damage: You are likely to be able to spot the caterpillars and their webbing on your box plant. Once they go to work, your box plant may be completely defoliated. Note - box tree caterpillar damage is entirely separate to the fungal disease box blight.
Favourite Plants to Consume: Buxus (box).
Ways to Tackle: Remove caterpillars by hand if possible. Encouraging more birds in your garden may help tackle them naturally, but is not known to what extent. Alternatively, consider insecticide for control or, as a last resort, choose an alternative plant. If your plant survives after an attack, keep it well fed to help regrowth.
A small number of pests have been found in limited numbers in the UK that present a real danger to plant, and in some cases human, health. Any sightings of these should be reported to the relevant authority.
Oak Processionary Caterpillar / Moth
First spotted in the UK in London in 2006, the oak processionary caterpillar has also been found in some surrounding counties. The caterpillars and their nests have long hairs that can cause an itchy rash or eye and throat irritations in humans and should not be touched. They should not be touched under any circumstances at any time.
The caterpillars feed on oak leaves and can leave the tree vulnerable to attacks from other pests and diseases. Any sightings should be reported to help control the spread of this pest.
Report via Forest Research Tree Alert portal