What's it look like?

As the name suggests, roses with this disease will have black spots on their leaves. The spots resemble ink blots up to 1cm in diameter. The leaves often turn yellow and drop off. The overall appearance of the plant can be weakened if it's severely affected.

What it attacks

Leaves of most rose bushes, especially in warm and humid weather.

What to do before it arrives

Install a drip system irrigation. Fungal spores are spread by irrigation water falling on unaffected leaves. Water in the morning only.

Choose disease resistant varieties - read your plant labels carefully. Plant roses in a bed of their own and only plant a border around the bed, not too close to the rose bushes. A border of chives is said to be helpful.

Don't bother growing roses in tropical areas.

Make sure there's good air circulation around plants. That means not planting them too close together.

Spray a preventative spray of diluted chamomile tea every week.

Keep them well fertilised with a good layer of compost and manure in late winter and again in summer.

What to do if you already have problems

Remove any infected leaves as soon as you see it occurs. Do not compost. Remove any fallen leaves from the ground near the plants. Apply fresh mulch.

Use drip irrigation instead of hose watering or sprinklers. Apply a seaweed solution to the plant regulary, this will toughen the new growth and give protection against the fungus.

Poor air circulation can increase the problem. Remove plants if they're overcrowded. Remove any lower growing plants nearby. Also prune your roses to an open vase shape, removing any inward growth to allow free air flow.

Use milk or chamomile spray and apply it every couple of days until it's under control. Then keep up a preventative spray every 10 to 14 days. Reapply after rain. A new organic fungicide "eco-rose" is made from potassium bicarbinate and is said to work well on black spot. Or you can simply try a home-remedy with a teaspoon of bicarb-soda, a tablespoon of white oil and 1.5 litres of water (recommended by the American Rose Society). Spray the entire plant and area surrounding with lime sulphur in winter when leaves are gone. This will kill any fungal spores that are lingering on the plant or on the ground.