Our gardens are our sanctuary, a place where we can escape into our own little patch of nature. We pride ourselves in the time and effort it takes to make our backyards one to show off. So, to ensure our gardens remain impeccable is to keep it healthy and one of the best ways to maintain a healthy garden is to familiarise yourself with the common garden pests and diseases.
Not every leaf spot, scab or miscolour is an indication of a pest infestation or fungal/bacterial disease, some symptoms are caused by planting conditions or environmental stress. It’s important to spot early signs of pests or diseases as precautions can be made to prevent any unwanted damage as the sooner a pest or disease is identified, the easier it is to eliminate.
But what are the main signs to look out for?
Here is some information and expert advice on the 10 most common pests and diseases of hedging plants in the UK, including what to look for and how to deal with them.
Firstly, pests. As all gardeners are aware, there’s always some kind of pest eating away at your plants, but that’s just nature. It doesn’t mean your garden is fighting off an infestation as the healthiest of gardens have all types of bugs which do a sterling job in all sorts of ways, from helping to decompose plant matter, enriching the soil, to aiding with pollination, letting your plants blossom. However, it’s the ‘bad bugs’ which warrant action. Here’s a list of the most conventional UK pests we encounter in our gardens and some advice on stopping them.
Aphids are the first on our list as this 3mm long insect is the most common pest your hedge plants will encounter. This sap sucking bug will usually infest young, soft growing tips of plants in spring and summer. With over 500 species in the UK, they are mostly referred to as ‘greenfly’ or ‘blackfly’ but come in all kinds of colours such as yellow, light green and even pink, with some covered in a woolly layer, as with the beech woolly aphid. Aphids multiply quickly, but move slowly so with early identification and correct methods of removal, they are relatively easy to control.
Aphids themselves are difficult to see however the impact of an aphid infestation is visible to the naked eye. Look for misshapen, curling leaves with a yellowing distortion. You can also check the underside of affected leaves as these troublesome bugs tend to hide there. If leaves or stems are covered with a sticky honeydew, this is an indication of an aphid infestation as this substance is produced by the insect as waste.
Natural predators will do their best to reduce the presence of aphids however you can get rid of them by wiping the infested leaves with a damp cloth or spraying with cold water. Chemical control is also available or use insecticidal soap or horticultural oil.
2. Scale insects
Another sap sucking insect, is the Scale, these are limpet-like insects with a protective shell-like casing. There are more than 25 species of scale insect and they are active all year round.
They weaken the growth of young plants, and some species produce white egg masses on stems and on the undersides of leaves. Like aphids, they too leave behind a sticky honeydew substance as a manifestation of their presence.
It is possible to remove scale insects with a brush and warm soapy water or you can purchase an effective insecticide spray.
3. Winter moth caterpillars
When discussing winter moth caterpillars, we are not referring to one specific pest. Winter moth is a common name given to the species that have adult moths, they are present and lay eggs from November to April. This name can be deceiving to us gardeners as these insects do all of their damage during the caterpillar stage and can lead us searching for the wrong pest. The caterpillars appear in spring, chewing their way through new growth, leaving holes in leaves and disfigured foliage behind.
Using pesticides in late March to April will prevent winter moths from infesting your plants as they have not hatched, leaving them vulnerable to chemical control. In conjunction with this, attracting birds to your garden is an effective way of eliminating hatched winter moth caterpillars. These insects are favoured among bird species such as tits, so encouraging them with the correct bird food or planting bird friendly hedging will benefit you and your efforts to prevent a winter moth caterpillar strike.
4. Spider Mites
If you’re a greenhouse gardener, these insects may be your number one enemy as they enjoy wreaking havoc on indoor plants, but will also enjoy attacking outdoor plants, especially Buxus sempervirens. Spider mites are made up of around 1,200 species, live in colonies and are often found on the underside of plant leaves. They leave tiny yellowish green mites and egg shells under affected leaves and if left untreated, a heavy infestation will see fine silk webbing in addition to leaves losing their colour, turning yellow, and may dry up and fall off.
We recommend discarding the use of pesticides as they are quick to develop resistance to them. Regular clipping of the hedge, ensuring that the clippings are disposed of immediately, is an effective way to prevent spider mites from infesting your healthy plants. Insecticidal soaps, horticultural oil or simply washing your plants with a strong blast of cold water are all valuable methods of removing spider mites.
5. Vine Weevil
Vine weevil is a beetle known to infest a wide range of ornamental trees, hedging plants and fruits with the tendency to favour plants kept in containers. These 10mm, dull black bugs can be found on plants in spring and summer and will leave irregular notches on the leaves as a sign of their plague. Adult weevils are difficult to find as they mostly come out at night. Give your plant a good shake if there are vine weevils present, as they will fall off your plant when force is administered. In addition to the vine weevil beetle, in autumn and winter, root-eating, soil borne grubs target the roots of a plant which will inevitably cause plants to weaken and die.
Precautions can be made to prevent a vine weevil attack such as chemical and physical control. Check your planting areas, root balls and pots for vine weevils before planting or repotting. There are also a number of insecticides that can be used to treat damaged plants and give protection against a potential attack.
It’s recorded that around 85% of most plant diseases are caused by fungal-like organisms. Their symptoms result in miscolouring, leaf markings and unusual substances covering the surfaces of plants.
1. Honey fungus
According to the RHS, honey fungus has been the most commonly reported garden disease for 20 years running and is deemed to be the most damaging fungal diseases in the UK. Made up of several destructive species, honey fungus spreads underground attacking the roots of healthy trees, shrubs, hedging, woody and perennial plants.
Honey fungus hinders the growth of developing leaves, whilst causing mature leaves to become pale. At ground level, white fungal growth appears between bark and wood and in some cases, golden brown mushrooms appear briefly on infected stumps, usually in autumn. Honey fungus is a tough disease to get rid of, often digging out the affected shrubs and surrounding plants is the only option to minimise potential spread to other parts of the garden. If you have a known honey fungus contamination in your area, we have a number of plants resistant to this disease. Species such as Box, Hornbeam, Griselinia, Lavender, Lonicera nitida, Yew, Holly, Hebe, Hazel and Blackthorn – all are great choices.
2. Powdery mildew
Powdery mildew is a fungal disease which occurs on specific species and targets the foliage and stems. Often associated with water stress, powdery mildew appears in summer and autumn. If your plants are experiencing this disease, it can be easily identified as a white powdered substance will be materialise on the foliage.
You can neutralize powdery mildew both naturally and chemically. Raking autumn leaves and disposing of them will impact the level of water stress your diseased plants will encounter. There are also heaps of chemical products to treat powdery mildew.
Phytophthora is a genus of plant-damaging Oomycetes that can also have a negative effect in natural ecosystems. This fungal disease attacks the root system and is the common cause of root and stem base decay of a wide range of trees and shrubs. Its presence derives from heavy or waterlogged soils causing large roots to appear blackened and finer roots to rot away. Above the ground symptoms arise once the root decay is well advanced. Deciduous plants will yellow and branches are likely to die back, whereas conifer plants will turn a dark matt green or brown.
As this disease is caused by waterlogged soil, it is important to improve the drainage with grit or land drains and for potted plants, ensure the pots have an effective drainage system. If you are experiencing a Phytophthora infestation, remove and destroy all infected plants and replace topsoil in effected areas as soon as possible. To fully avoid this disease, you can plant species which are less susceptible to Phytophthora, such as Berberis, Hornbeam, Leylandii, Hazel, Hawthorn, Photinia and Western Red Cedar.
1. Bacterial Canker
Bacterial Canker (Pseudomonas syringae) is a disease caused by two closely related bacteria that affect the stems and leaves of a number of the Prunus genus, although Prunus laurocerasus (Cherry laurel) and Prunus lusitanica (Portuguese laurel) are more resistant to this bacterial disease than their relative species.
This disease is also known as ‘shothole disease’ as infected plants display small brown patches on its leaves in midsummer, which eventually fall out to leave small round holes. Alongside these unsightly leaf disfigurations, sunken dead areas of bark will joined by a gluey ooze.
To prevent Bacterial Canker from infecting your plants, carrying out all pruning in July or August when tissues are more resistant is an effective way to reduce the chance of infection. On infected plants, cut out all cankered areas, pruning back to healthy wood. You can then paint all pruning wounds with a wound paint to protect your plant from reinfection. While mentioning the possibility of reinfection, it’s important to remove and destroy these cuttings.
2. Fire blight
Hedging plants such as Cotoneaster, Hawthorn, Photinia and Pyracantha can be effected by this waterborne bacteria. Most apparent in late spring and autumn, this disease attacks the shoots of blossoms, giving the plant the appearance of drying out and sun scorching. Cankers on branches, especially where infected shoots join larger branches appear and a slimy white liquid will leak from infections in wet weather.
Prune and destroy all signs of infection immediately, soaking your cutting tools with disinfectant between cuts to avoid spreading the bacteria. Jersey fluid or methylated spirits are recommended by the RHS.
Box Blight & Caterpillar
You may be familiar with this term and it may be something that is currently invading your gardens. Box blight is a disease found on box (buxus semperviren) leaves from the fungus Cylindrocladium buxicola (syn. Calonectria pseudonaviculata). The disease can be spread by wind driven rain, overhead irrigation, animals (pets catching the disease on their fur and transferring it onto your box). We hate mentioning Box blight in a blog because we wouldn’t want people to be put off the classic Buxus sempervirens – it’s one of our top 10 sellers (literally tens of thousands of plants per annum) and we have not once ever in over 8 years had a customer report blight following supply of our plants. The symptons of box blight are:
- Leaves turn brown and fall, leading to bare patches
- Black streaks and dieback on young stems
- In wet conditions the white spore masses of the fungus may be seen on the undersurfaces of infected leaves (place leaves in a plastic bag with moist tissue for a few days to check). Note that spore masses of Volutella blight will look pink. taken from RHS
Box caterpillar was first found in 2007 and first sighted in the UK in 2008. It is in season from mid-March to October. Box tree caterpillars feed within webbing and can completely defoliate box plants. The caterpillars are a lot more prominent in the south of the UK. See EBTS (European Boxwood and Topiary Society) for their map of caterpillar recordings.
Here at Hedges Direct, we ensure that all of our stock is pest and disease free. If you are experiencing any of the symptoms mentioned above but are unsure on whether you can correctly diagnose your plants, we have an expert service team who are more than happy to help identify any pest or disease infestation and offer advice. We simply require you send in some pictures of the plants in question to firstname.lastname@example.org