Rose bushes and flower seedlings, shrubs and trees, vegetable plots and fruit crops, house plants and even the lawn are all in danger of succumbing to the UK’s most common plant and garden diseases, whether they be fungal, bacterial or viral. Here’s how to spot and treat them.
This disease (right) grows mostly on the upper surface of leaves and will occasionally spread to the underside and other parts of the plant. It thrives in dry soil conditions, but where overhead conditions are a little humid. A whole host of plants, including herbaceous and many ornamental, can be at risk from a powdery mildew infection.
What to look for: As the name suggests, it is characterised by a white powdery fungus coating on the leaves.
How to treat: Remove and destroy all infected parts of the plant and be careful not to transfer spores on to healthy foliage. Try not to add too much nitrogen-rich fertiliser as this can promote sappy growth which is more vulnerable to fungi. If opting for chemical solution, choose a fungicide containing penconazole. If looking for a suitable organic treatment, choose a dispersible sulphur spray.
Botrytis (or grey mould) is often found on indoor cyclamen and outdoor flowers, such as lily and chrysanthemum, which are kept in very humid conditions.
What to look for: It looks like a grey furry mould and can be found on leaves, petals and the base of stalks.
How to treat: Pick off the affected part of the plant and reduce any humidity by increasing space between plants, encouraging air movement. Destroy all plants which are severely affected, and avoid over-feeding with a high nitrogen fertiliser as this encourages soft lush growth that is more susceptible to attack. No fungicide treatments are currently available on the market for home gardeners, but a recommended organic remedy is lime sulphur.
Clematis wilt mostly strikes early, large-flowering varieties.
What to look for: The top of the clematis can wilt, collapse and eventually die. The diseased shoots turn brown and hang loosely from the main stems.
How to treat: Cut out all affected shoots and, if the entire plant is affected, cut it down to ground level and feed with a good liquid fertiliser. Initial planting of the clematis several centimetres deeper than normal allows for the development of healthy shoots beneath the surface as replacements. There's no ready-made chemical treatment, but spraying the soil around the plant with a fungicide containing penconazole can help healing.
This disease (left) is extremely common in seedlings and is usually caused by over-watering, crowding of seedlings, poor air circulation, dirty containers, infected soil or contaminated water.
What to look for: Damping-off disease causes emerging seedlings to rot off at soil level, collapse easily and lose their leaves early.
How to treat: Sow your seeds thinly in good compost and clean pots, then dampen in moderation with fresh water and make sure there is the necessary ventilation. And avoid sowing seeds too thickly. For a chemical treatment, try one of the many copper-based fungicides on the market in the seed trays.
Leaf spot is a common plant disease, easily noticeable, and caused by a combination of bacteria and fungi.
What to look for: Leaf spots can be of various colours such as grey, brown or black, and can affect all types of plants. Spots can sometimes join together to form larger areas of dead black tissue.
How to treat: Immediately remove and destroy all infected foliage, and to reduce the chances of re-infection for the following season, prune shrubs back hard and water sparingly for a few weeks. For a non-organic treatment, spray with suitable fungicides (containing myclobutanil) and continue spraying at fortnightly intervals throughout the season.
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