Post category: Weeds, Pests and Diseases
Greenflies can infest roses and cause reduced growth. Usually they are controlled by ladybirds or other natural agents but a heavy attack may need to be controlled with an insecticide, which are contained in most rose sprays.
Always keep roses free of weeds. A formal rose bed must be kept weed-free, neatly edged and tidy. Straighten and trim lawn edges in March. Remove all existing weeds.
Rose blackspot is inevitable in areas of high rainfall, especially in wet seasons. It causes black spots on the leaves, which then fall off. Some varieties are more susceptible than others but most are susceptible to some strains of the disease.
A spray of Multirose or Roseclear, or similar as the buds break in April, is essential. Spray again in May and June, and more often in a wet season, or a wet locality.
Rose mildew is generally only serious on ramblers. White chalk-like fungus grows on the leaves and stems. With susceptible varieties, spraying with Roseclear or Multirose will be necessary, starting in April. Mulching helps. Plant climbers instead of ramblers on walls.
Rose rust is an occasional problem but serious in some areas when it does occur. Rusty spots appear on the underside of the leaves. Spray with Dithane or Liquid Copper when the disease is first seen.