Roses With Black Leaves

Roses are beautiful flowers when healthy and flourishing. If your rose leaves start to spot and turn black, you may have a problem with black spot disease.

Facts

• According to the University of Maine Cooperative Extension, black spot is one of the most common rose diseases. Diplocarpon rosae, also known as black spot, will weaken the plant and limit bloom production if not treated.

Identification

• Black spot normally affects the upper surface of rose leaves. Spots commonly have fringed borders, and may reach up to ½ inch in diameter. If the disease is left unchecked, leaves may turn yellow and drop from the plant.

Growth

• Black spot spores thrive best in temperatures between 65 to 75 degrees Fahrenheit. In order for the spores to properly germinate, the spore must be wet for at least seven hours.

Prevention

• Apply a fungicide specifically for treating black spot as a means of preventing black spot. Limit risk of infection by removing any fallen leaves from the flowerbed, and prune infected areas until you reach clean white wood. Ohio State University Extension suggests keeping foliage dry.