Clematis Care : Clematis Diseases and Pests

Clematis Diseases and Pests

Animal pests

Climbers are not particularly prone to attack from the variety of wildlife that can wreak havoc with other less robust plants. In general they are remarkably resistant, and the amount of growth they produce in a season soon covers up the odd nibbled leaf. The climbing roses are of course prone to the same problems as their non-climbing relatives, and can therefore be dealt with in a similar fashion.

clematis wilt

The list that follows is designed to help you isolate potential problems. It should not put you off growing these wonderful plants.


Aphids

This is the name given to the group of pests that includes the well-known greenfly and blackfly, which attack nearly every plant at some time during the growing season. They suck the sap from the young shoots, and cause stems and leaves to curl, generally in a downward direction. They also exude a sticky residue that is much loved by ants, which are often seen moving up and down a badly infected plant. In severe cases a black mould forms over the surface of the leaves.

Gardeners are often confused by the mass of white specks which appear during an aphid attack. They sometimes mistake these for whitefly, when in fact they are the husks of dead aphids.

Aphids can be controlled by a vast array of chemicals, many of which only kill off the aphids, leaving the beneficial lacewings, ladybirds and hover-flies to carry on their own form of pest control.


Earwigs

These rather lovable creatures are responsible for chewing chunks out of leaves and flowers, especially those of clematis, to which they are very partial.

Earwigs are also rather difficult to control. For as they only venture out during the night, no amount of spraying will have the slightest effect. The various dusts that are recommended for the purpose will simply make your plant look as though it has a terminal case of mildew.

There is a much simpler and more effective plan of attack. All you need to do is to place the skin of half a grapefruit at the base of the plant. The earwigs will return to spend the day underneath it, at which point both the grapefruit skin and the earwigs can be disposed of together.


Froghoppers

These pests are responsible for the frothy mass known as cuckoo spit. This hides a small green insect, which sucks up sap and in severe cases can severely stunt the growth of the plant.

Froghoppers can simply be washed away with a forceful stream of water from your sprayer before they can do any damage.


Scale Insects

Sometimes small brown scales appear on the leaf undersides of evergreen climbers (Clematis armandii is especially prone). Also, as with aphid attacks, a black, sooty mould covers the leaves. The little beast involved is the scale insect. Under each brown hump lives a small bug, which sucks the sap from the plant.

Because scale insects colonise the underside of leaves, they often build up large colonies before you notice them. They are also rather difficult to control. Only repeated sprays of a good systemic insecticide in the early spring will have any effect. Mercifully, scale insects are not particularly common, and are more liable to appear on evergreens grown in a conservatory.


Slugs and Snails

No section on pests would be complete without some mention of these two doyens of the plant-eating world. Slugs and snails do more damage to clematis than any other creature, with the possible exception of a gardener using a hoe. It’s usually the slugs that devour the succulent basal shoots, while the snails’ ability to climb gives them access to a hearty meal from the flowers.

There’s a huge armoury of control methods available, but none so effective as placing a layer of sharp grit around the base of the plant. Slugs and snails hate this. What is more, you only have to do it once and the grit doesn’t get washed away.


Mice

These little rodents can do vast amounts of damage in winter, especially if you are growing clematis through heathers. The covering of heathers makes an ideal winter habitat for mice, and they don’t have to go far for a meal.

Growing clematis through a clay drainpipe for the first foot will help to control this problem. But a cat is probably the best answer. Mouse traps are not a good idea. It’s so easy to forget where you’ve set one in a bed of heathers, with dire results to your fingers when you start weeding the following spring.


Ants

Sometimes plants wilt and die for no apparent reason, particularly those planted at the base of a wall. Should this occur, it’s always a good idea to check around the base of the plant for an ants’ nest. These creatures make a vast complex of tunnels when creating their nests, and this sharpens the drainage so much that the climbers suffer from drought.

Ants can be easily dealt with by sprinkling an ant powder over the soil surface.


Fungal (Climber and Clematis) Diseases

Provided you water and feed your plants correctly, and don’t leaving any jagged shoots when pruning, and remove dead leaves and other debris on a regular basis, then you probably won’t need to read this section.

Plants are living things, and diseases generally strike those which are weak and undernourished – not those which have built up a strong immune system. The clematis diseases that follow are the ones most usually encountered. All of them can be controlled by cultivation methods and the occasional spraying.


Clematis Wilt

This is the name that strikes terror in the heart of many gardeners. It first became a problem in the early part of the century, and ever since then discussions have raged as to what it is and how it can be controlled.

The symptoms are dramatic but not necessarily terminal. Wilt usually strikes just as the clematis is about to flower: the first signs are a slight greying of the leaves, followed by a total collapse of the plant (though sometimes only one shoot is affected) as though it has suddenly dried out. At this point many plants are consigned prematurely to the bonfire – which is a mistake, as they can often recover.

Clematis wilt is thought to be caused by a fungus, which attacks the plant at the point where the soil and air meet, blocking the flow of sap and thus causing the plant to wilt. It must be said that on many occasions the same symptoms can be due to mechanical damage. One of the stems may have been cut by a hoe or damaged by the pet cat. Either way the treatment is the same.

Cut out and burn all the dead and dying shoots down to ground level, and give the plant a good soaking. Provided that you’ve planted it correctly and buried a few buds beneath the soil, the plant stands a good chance of recovery. Some precautions against slugs will allow shoots to come up from below ground level, and very soon the plant will be back to full vigour.

Certain clematis varieties seem to be more prone to wilt than others. These are the ones that have caused the most problems in the past:

• C. ‘Countess of Lovelace’

• C. ‘Moonlight’

• C. ‘Duchess of Edinburgh’

• C. ‘Marie Boisselot’

• C. ‘Horn of Plenty’


Mildew

This clematis disease strikes mainly those clematis plants growing in the shade, and where there is poor air circulation. It can be recognised from the white powdery markings on the leaves, which if it is left unchecked will eventually turn brown and die. The later-flowering varieties are also more prone to attack.

Mildew can be easily controlled by a preventative spray with a specific fungicide.


Grey Mould

This fungus can be discerned from a light-grey fluffy growth that starts to form on dead leaves, usually in the autumn. If left untreated, the disease will spread rapidly to the living parts of the plant.

The best cure is prevention. Remove all dead material from around the plant. This fungus is also more prevalent on plants grown in a conservatory, where good ventilation will keep it at bay.


Clematis Care – Other Problems

Bottom leaves dying This is perfectly normal. It will happen during the late summer period, particularly to the later-flowering varieties. As the plant grows it has no more use for these bottom leaves, so discards them to save energy for flowering.


Green Clematis Flowers

The early-flowering hybrids are the most prone to this problem, which flower arrangers love to make use of. It is caused partly by the weather and partly by a lack of potash. A good feed with tomato fertiliser will soon rectify the problem.


No Clematis Flowers

Sometimes, for no reason, a clematis will ‘go blind’ and fail to flower. High-potash fertilisers will help to alleviate the problem, as will pruning the shoots back by half, which will sometimes make the clematis produce flower buds later in the season.


24. September 2010 by Dave Pinkney
Categories: Climber Plants | Tags: | Comments Off on Clematis Care : Clematis Diseases and Pests

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