Fungus on Roses

Growing beautiful roses is one of the great achievements for the home gardener. Unfortunately, many roses are vulnerable to fungal diseases. A few basic steps will go a long way toward controlling fungus in the rose garden.

Disease Identification

• Gardeners may encounter one or more of the three most common rose diseases. Powdery mildew appears as a gray powdery film on leaves and stems. Rust infects rose leaves with red-brown spots and splotches. Black or brown spots, followed by leaf yellowing and leaf drop, are the telltale signs of black spot, the most serious rose disease.

Causes

• Fungal diseases thrive in moist conditions. Crowded and overgrown rose canes, as well as those lying on the ground, stay damp and are susceptible to fungus. Roses planted in shade do not dry out as quickly as those in full sun. Overhead watering causes unnecessary and prolonged moisture.

Prevention

• Improve air circulation by keeping plants pruned of dead, diseased and crossed branches. Rake up fallen leaves and petals as soon as they fall to keep spores from splashing up onto the lower leaves of bushes. Keep the plant healthy with adequate watering and fertilization.

Chemical Treatment

• If good rose culture and regular cleanup don't rid your roses of fungus, you will need to use a fungicide. Use a horticultural soap or garden fungicide formulated to control rose diseases.

Plant Selection

• Choose roses that are disease-resistant. Disease resistant bushes include Just Joey, Keepsake, Silver Jubilee and Tournament of Roses. Resistant climbers include Dublin Bay and Royal Sunset.