Regional Growing Guide: Mid-Atlantic

Keeping Beautiful Roses Disease-Free

Roses are a favorite in so many gardens. But let's face it, those gorgeous flowers are sometimes accompanied by various rose diseases and pests. Is there an alternative to regular pesticide applications to keep these beauties producing the blossoms we so covet? Definitley, but it takes starting with the right rose and just a little care throughout the season.

Resistant Varieties
The first practice of a good rose grower should be to grow disease-resistant roses. Chosing any of the our AARS winning roses is a perfect place to start. You can visit one of our accredited public rose gardens to see these roses in the garden environment and chose the one that will be perfect for your needs. This will start you on your way to selecting roses for your own garden.

Another way to find the right rose for your garden is to read the most recent literature and catalogs. Breeders are constantly working on developing resistant roses, and the varieties available are expanded every year. One tip: a rose with a particularly leathery, puckered leaf is usually more resistant to leaf problems than one with smooth leaves.

The most common rose diseases are black spot, rust, and powdery mildew. All are fungal diseases, spread by spores being washed or blown onto leaves and stems.

Learn to Recognize Diseases
Black spot starts as tiny black flecks that turn into larger circular black spots. Eventually the spots coalesce into large lesions and cause the leaf to yellow and fall off. The spots appear on leaves and stems, and spend the winter on fallen leaves and infected canes.

Powdery mildew appears first as very small blister-like areas on young leaves, causing them to pucker. As spores reproduce, the leaf and flower buds become covered with a gray-white powder.

Rust, as the name implies, appears as rust-colored spots on foliage.

Preventive Strategies
Research has shown that black spot spreads most readily when foliage is wet. Therefore, planting in full sun, pruning to keep the shrubs open to circulation, and watering only at ground level will help prevent infection.

Powdery mildew, however, is best prevented by wetting the leaves since it needs dry conditions to thrive. A strong water spray several times a week will help prevent infection. As a bonus, this also helps control pests such as aphids and spider mites.

Another preventive method for diseases is to remove all foliage on the plant and on the ground in late fall, and to prune the tips of the canes. Both pathogens overwinter in fallen tissue and in the leaf buds just below the flowers. Pruning and clean-up get rid of many overwintering spores. If the canes are badly infected, a rose can be pruned to 4 to 6 inches from the graft with no harm.