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Pests and Diseases on Roses

Pests and Diseases on Roses

Roses are very tolerant plants but if they are not taken care of they become spindly and unattractive, producing few if any flowers. Neglected roses are also more susceptible to pests and diseases, especially when they are also being grown in the wrong place. If pests attack roses, it may be because they are not properly looked after and heavy prolonged rain can also cause fungal diseases and this in turn makes roses more vulnerable to pests.

Diseases
If roses are not properly looked after they become susceptible to diseases and pests. Heavy prolonged rain plus humid conditions can also cause fungal diseases.

Mildew. Mildew is a fungal disease that affects the stems, buds and leaves of roses. It appears like a covering of white dust and roses are more prone to it if they are over-fed or left to dry out in dry weather. Roses must be sprayed with a fungicide and if mildew is very bad, the affected areas must be cut out.

Blackspot. Leaves are covered in round brown or black spots and fall prematurely. Collect and dispose of all affected leaves but don’t put them it the compost bin as the fungus will only be spread around the garden. Feed and mulch the roses regularly and if the black spot is very bad spray with a fungicide.

Rust. Yellow swelling on the undersides of the leaves, turning black in autumn or leaves falling prematurely are the symptoms of Rust. It can be prevented by mulching well, picking up fallen leaves to prevent further infection or spray with a fungicide.

Pests
Pests are much easier to identify than diseases and the majority of them are clearly visible on leaves, flowers and fruit. With a few exceptions they are also easier to control than diseases.

Aphids - These are black, green or reddish insects that damage the leaves, buds and young shoots of roses and they leave a sticky secretion on the leaves. Lavender, marigolds, nasturtiums and cress are all believed to repel aphids when planted underneath roses. Aphids can be dislodged by simply spraying them with a powerful jet of water, spraying with a solution of washing-up liquid or if infection is very bad it is essential to spray with an insecticide.

Caterpillars - Most caterpillars eat holes in the leaves and in severe infestation they may even defoliate them. You should open curled leaves and investigate the contents of webbing to see if caterpillars are the cause. If caterpillars are few and not stripping foliage rapidly, they can usually be controlled by hand picking. Where they are present in large numbers then an insecticide will have to be used.

Earwigs - These brown insects are normally not seen during the day as they feed at night. They shred the leaves and flowers of roses although they also eat some aphids so they are not always a huge problem. They can be trapped with straw stuffed into inverted pots and supported on a cane among the plants.

Whitefly - Whiteflies are tiny white moths, often rising in a cloud-like dust when the plant is disturbed. They will be found on the young shoots of roses but they are not as easy to control as greenfly and blackfly as their life cycle in very complicated and if they become a problem the use of an insecticide is the only solution.

You may be doing all you can, planting your roses in the best position, choosing disease-resistant varieties and watering and feeding them properly but if they are still suffering from pests and diseases you will need to take positive action. For organic or chemical control for these pests and diseases contact the staff at Garden Creation Garden Centre.

Jobs of the week
* Begin to sow seeds of summer bedding in seed trays.
* Apply slug control around emerging lupins, hostas delphiniums and other susceptible plants.
* Prune roses and spray with a pest and disease control.
* Begin to feed indoor plants and repot if necessary.