Holes in your leaves? Larve in your soil?
We keep all of our stock pest and disease-free, however we know that sometimes an existing hedge may need a little TLC, so we've put together a guide on the most common problems gardeners face from pests and diseases in the UK.
Not surprisingly aphids are the most common pest you will encounter in your hedge, there are over 500 species in the UK. Aphids are sap-sucking bugs, around 3mm long, that usually infest the young soft growing tips of plants in spring and summer. They are most often encountered as ‘greenfly’ or ‘blackfly’ but come in several other colours, they may also be covered in a woolly protective layer, as with the beech woolly aphid.
|Symptoms||Infestations of young shoot tips, visible to the naked eye, often accompanied by the distortion of young plant growth and general weakening of the plant. |
A sticky honey dew exuded by the aphids that can result in the growth of black sooty moulds, (not in themselves harmful to the plant).
|Natural Control||Encourage natural predators such a ladybird and hoverfly larvae. |
Small infestations can be wiped off with a damp cloth.
|Chemical Control||There are a number of pesticides on the market for the control of aphids in hedges, the most effective will contain Deltamethrin or Cypermethrin. Always read the label and follow the manufacturers’ instructions.|
2. Scale insects
A sap-sucking insect that has a protective shell-like scale that covers its’ body, often resembling small limpets, there are a number of species in the UK which can affect hedging.
|Symptoms||Small bumps found on the underside of leaves or on the stems of woody plants. Some species exude a sticky white covering in summer to protect their eggs, and this can often be the first time they are noticed. Light infestations will cause few problems.|
|Natural Control||On woody stems, the scales can be removed with a brush and warm, soapy water.|
|Chemical Control||Product containing Deltamethrin or Cypermethrin will be most effective, spray in May/June. Always read the label and follow the manufacturers’ instructions.|
3. Vine Weevil (Otiorhynchus sulcatus)
Vine weevil is a beetle that attacks a wide range of plants, including hedge plants.
|Symptoms||Adult weevils, which are a dull black colour and around 10 mm long, can be found on plants in the summer. They eat the leaf margins and leave them with irregular notches.|
The grubs are around 5-10 mm long, creamy white in colour with tan-brown heads, they live in the soil and eat the fleshy young roots in autumn and winter. This can result in wilting and death of the plant.
Adult weevils are difficult to find, coming out mostly at night. It is possible to place an upturned umbrella under the shrub and give it a good shake to capture the weevils in the brolly.
To control the larvae use the microscopic nematode Steinernema kraussei available from garden centres. This tiny creature invades the body of the grub and kills it. For best results, water into the soil in August or September when the soil temperature is still warm enough for the nematode to be effective (5-20ºC) and before the vine weevil grubs have grown large enough to cause serious damage.
|Chemical Control||There are no chemical control methods available for application to the soil around plants, though a product containing acetamiprid is available for pot grown plants.|
4. Winter Moth Caterpillars
Winter moth is a general name given to a number of species that have adult moths that emerge and lay eggs between November and April. The small caterpillars emerge in spring and eat holes in young and developing leaves of a wide range of deciduous trees, shrubs and hedge plants.
Attacks by winter moth caterpillars are first noticed in spring when young emerging leaves are eaten.
The damage is often first spotted in summer when the leaves are fully grown and the small holes made during the spring have enlarged with leaf growth, by this time the caterpillars have already left the plant.
|Natural Control||Encourage birds into your garden, especially tits, who feed these small caterpillars to their young in the spring.|
|Chemical Control||There are a number of pesticides on the market for the control of caterpillars, the most effective will contain Deltamethrin or Cypermethrin. Always read the label and follow the manufacturers’ instructions.|
5. Spider Mites
There are a number of species of these small sap-sucking pests, and they are most commonly found in greenhouses. However, in warm dry summers, they can become a problem for plants growing outdoors too, particularly for box hedging.
|Symptoms||Plants infested with spider mite show a fine pale mottling on the upper leaf surface. The underside of the leaves have many tiny yellowish-green mites and eggshells. These are more easily seen with the aid of a magnifying lens.|
In heavy infestations, you may see fine silk webbing on the plants, and the leaves lose much of their green colour.
|Natural Control||Spider mites are unlikely to become a major pest outdoors, so could easily be tolerated. As they infest the young growth they can be controlled by regular clipping of the hedge and then burning the trimmings.|
|Chemical Control||Products containing acetamiprid will give some control, always read the label and follow the manufacturers’ instructions|
6. Powdery Mildew
Powdery mildews are fungal diseases of the foliage and green stems and are often specific to individual species. They are usually superficial as they cover the surface of the leaf. Powdery mildews have a relatively high water content and can survive in dry conditions and so are often associated with water stress in the host plant.
|Symptoms||A white, powdery spreading fungus that can cover leaves and green stems in late summer and autumn. Leaves and young tissues can become distorted and stunted.|
|Natural Control||Water plants in dry weather to reduce stress, particularly those that are newly planted. Rake up leaves in autumn and burn or remove, do not compost them as the spores overwinter in the dead leaf matter.|
|Chemical Control||Mildews are easily controlled with chemical as they only affect the surface of the leaf. There are a wide range of products available for the treatment of powdery mildew, those containing tebuconazole are very effective. Always read the label and follow the manufacturers’ instructions.|
7. Honey Fungus
There are several species of honey fungus, all in the genus Armillaria. This problematic fungus spreads underground attacking and killing the roots of trees, shrubs, hedging and herbaceous perennials. Beech, Photinia, Privet, Holly, Yew and Prunus species are all particularly susceptible.
Above ground the leaves of affected plants will become pale and poorly developed, there may be premature autumn colouring. Twigs and small branches may die back completely, particularly in dry weather.
|Natural Control||There is no known effective control for honey fungus. Remove all dead and dying material from the soil and burn if possible. Replace topsoil if practical to do so. (See appendix I for more resistant species).|
A large genus of microscopic pathogens often described as a fungus, and though they resemble a fungus they are distinctly separate.
|Symptoms||Above ground, the foliage of deciduous plants will yellow and twigs and branches may die back. In conifers, the foliage will turn a dark matt green or brown. These are symptoms indicative of poor water uptake, as the roots are progressively destroyed, and could be mistaken for drought or honey fungus.|
Below ground, smaller roots will have rotted away and larger roots will appear blackened and will be soft and easily broken. As this is a microscopic pathogen there will be no visible signs of its presence.
|Natural Control||Improve the soil drainage with grit or land drains. Remove and destroy all infected plants and replace topsoil in the immediate vicinity if practical to do so. Plant with less susceptible species, (see appendix II).|
|Chemical Control||There is no effective chemical control for phytophthora in the soil.|
9. Bacterial Canker (Pseudomonas syringae)
Also known as ‘shothole disease’, bacterial canker is a waterborne disease that affects Prunus species. Prunus laurocerasus (Cherry laurel) varieties and Prunus lusitanica (Portuguese laurel) are more resistant than any other Prunus.
|Symptoms||Small brown patches will appear on the leaves from midsummer, the centre of these falls out to leave a small round hole, giving it the alternative name of shothole. |
On the branches, sunken lesions or dead areas will appear, often accompanied by a sticky amber coloured ooze. In severe cases, whole branches will die as the lesions cut off the sap flow.
|Natural Control||The bacteria are waterborne and can be carried by rain or fog. They can enter leaves through tiny breathing holes called stomata. |
Restrict the pruning of Prunus species to July and August when the plants are most resistant. Paint all pruning wounds with a sealant containing copper.
|Chemical Control||There is no effective chemical control once the disease is present.|
10. Fireblight (Erwinia Amylovora)
A disease caused by waterborne bacteria that affects members of the Pomoideae family. Hedging such as Cotoneaster, Hawthorn and Photinia can be affected.
|Symptoms||The disease most often enters a plant through the blossoms in spring, causing them to wilt and die, remove blossoms if you suspect infection. In late spring and summer, shoots may shrivel as the infection spreads through the inner bark. In damp weather, a slimy white exudate may be present on the infected tips.|
|Natural Control||Prune out and burn all signs of infection immediately, clean secateurs with Jeyes Fluid or formaldehyde to avoid spreading the infection.|
|Chemical Control||There is no effective chemical control for fireblight.|
Appendix I – Hedging plants more resistant to honey fungus
Appendix II – Hedging plants more resistant to Phyophthora