By Stan V. Griep
American Rose Society Consulting Master Rosarian – Rocky Mountain District
Botrytis blight fungus, also known as Botrytis cinere, can reduce a blooming rose bush to a mass of dry, brown, dead flowers. But botrytis blight in roses can be treated.
Symptoms of Botrytis on Roses
The botrytis blight fungus is sort of grayish brown and looks fuzzy or wooly. The botrytis blight fungus seems to attack mostly hybrid tea rose bushes, attacking the leaves and canes of the subject rose bush. It will prevent the blooms from opening and many times causes the bloom petals to turn brown and shrivel up.
Botrytis Control on Roses
Rose bushes under stress will be extremely vulnerable to this fungal disease. Make sure that you are caring for your roses properly, which means making sure your roses are getting enough water and nutrients.
Rainy and high humidity climatic conditions create just the right mix to bring on an attack of botrytis on roses. Warmer and drier weather takes away the humidity and moisture that this fungus loves to exist in, and under such conditions this disease will usually discontinue its attack. Good ventilation through and around the rose bush helps keep the humidity buildup within the bush down, thus eliminating a favorable environment for the botrytis disease to get started.
Spraying with a fungicide can give a bit of temporary relief from botrytis blight in roses; however, the botrytis blight fungus does become quickly resistant to most fungicidal sprays.
Make sure that if you have a rose with botrytis blight you are careful to discard any dead material from the plant in the fall. Do not compost the material, as botrytis fungus can spread the disease to other plants.