Get '101 tips to a great rose garden' NOW! >>>

Ready To Make Your ROSE GARDEN
The Envy Of Neighbours?

Black Spots

Black spots are a fungal disease that causes the canes to turn black or brown in spots on the foliage. To remedy this, simply prune the affected areas and throw out the clippings. Do not water the head to prevent this from happening again.

This fungal disease is most severe in wet years and is spread by splashing rain throughout the growing season. A symptom of this disease is circular black spots with feathery margins on the upper leaf surface. Occasionally, yellow rings surround these spots. Infected leaves eventually turn yellow and fall from the plant. Excessive defoliation may weaken plants, making them more susceptible to cankers and winter injury. Canes may also be infected with stem lesions appearing red to purple in color.

Black spot management should begin with good cultural practices. Maintain plant health by properly watering and fertilizing plants. To reduce the number of spring infections, prune out infected canes and dispose of all plant debris, including leaves after the growing season.

To limit the number of infections during the growing season, minimize water splash by mulching around the base of plants and watering at ground level. Fungicides may also be needed as a protective treatment during rainy periods or for severely infected plants.

Fungicide application generally begins in early summer with the development of leaf spots. A variety of fungicides are currently labeled for black spot. Carefully read the label before buying, opening, and using fungicides.

Black spot is caused by a fungus. It is one of the most common diseases and is found everywhere roses are planted. It does not kill the plant outright but over time the loss of leaves can weaken the plant making it more susceptible to other damages. The disease is active during cool, moist weather.

The disease can be recognized by black spots one-tenth to one half inch in diameter that develops first on upper leaf surfaces. Areas adjacent to the black spots turn yellow and leaves drop prematurely. This disease usually begins at the bottom of the plant and progresses upward. Sometimes, raised purple-red irregular blotches also develop on immature wood of first year canes which later becomes blackened and blistered.

Sanitation is the first line of action to prevent your roses from black spots. As soon as the diseased leaves are noticed, remove and dispose of them. Dead leaves on the ground should also be collected and destroyed. To minimize overwintering of the disease, remove all leaves from the ground in the fall and prune diseased canes before growth begins in spring.

To prevent spread of the disease, keep the foliage dry as the fungal spores need a wet surface to germinate and cause infection. Do not use overhead watering, or, if you do, water early in the day so the foliage is dry by nighttime. Also, prune plants to allow proper air circulation and facilitate the drying of foliage.

Fungicides applied as a preventative spray can give good control but they need to be applied regularly. They will not cure infected leaves, but will prevent infection of new leaves. Some registered fungicides include: triforine available as Ortho Funginex, chlorothalonil available as Security Fungigard or Ortho Daconil 2787, and wettable dusting sulfur. Many other products listed as rose dusts are also effective.

Avoid highly susceptible cultivars including most yellow and copper-colored roses. Roses reported to be highly resistant are; Fortyniner, Coronado, Tropicana, Europeana, Queen Elizabeth, Carefree Beauty, Simplicity, Bonita and Grand Opera. Ask about other cultivars at your nursery.