INTRODUCTION

Black spot is one of the most common diseases of roses.  Black spot is a fungal disease caused by the fungus Diplocarpon rosae.  This disease has been in the United States since the early 1800's, and can now be found all over North America.  If black spot is not controlled, it can weaken your roses and lead to further problems.

SYMPTOMS

Round to sometimes irregular black spots form on leaves, normally on the upper side of the leaf.  Yellowing begins around these spots and spreads over the leaf surface.  Heavily infected leaves eventually drop from the plant.  An excessive amount of leaf loss causes a decline in the quality of the plant resulting in fewer leaves and blossoms, and reduced vigor.  Some resistant cultivars will get only small spots that will not cause yellowing or defoliation of the plant.  Varieties reported to be disease resistant are listed in Table 1.

Table 1 - Roses reported to be Disease Resistant (even resistant roses will sometimes get diseases)
Shrub Roses:	Rugosa Roses:	Hybrid Teas:	Floribundas and Grandifloras:
Alexander MacKenzie All That Jazz Ambridge Rose Cambridge Captain Samuel Holland Carefree Beauty Carefree Delight Carefree Sunshine Carefree Wonder Champlain Cuthbert Grant De Montarville Frontenac George Vancouver Henry Kelsey Hope for Humanity John Franklin Knock Out Morden Centennial Morden Sunrise Nearly Wild Scarlet Meidland Sea Foam William Baffin	Charles Albanel Dart's Dash David Thompson F.J. Grootendorst Henry Hudson Jens Munk Magnifica Polyantha Rosa rugosa Rosa rugosa 'Alba' The Fairy	Big Purple Carla Cayenne Charlotte Armstrong Chrysler Imperial Duet Electron First Prize Forty Niner Granada Miss All-American Beauty Mister Lincoln Olympiad Pascali Peace Pink Peace Portrait Pristine Proud Land Smooth Lady Sutters Gold Tiffany Tropicana	Angel Face Acadia Sunrise Betty Prior Carousel Cathedral Crimson Bouquet Europeana Fashion First Edition Gene Boerner Goldilocks Impatient Ivory Fashion Love Love & Peace Mirandy Montezuma Pink Parfait Prominent Queen Elizabeth Razzle Dazzle Red Gold Rose Parade Sonia Sunsprite
	Miniature Roses:
	Baby Love
Conditions favorable to the spread of this disease are temperatures from 75 to 85 degrees Fahrenheit, high humidity levels, prolonged wet conditions.  Young developing leaves are the most susceptible to infection.  The spores normally spread from splashing water, either by rain or overhead watering. PREVENTION - MAINTAINING HEALTHY ROSES Black spot can not always be completely prevented, but with proper care it can be kept to a minimum and to a level that will not be detrimental to your roses.  Follow these steps: Plant resistant varieties when possible. When planting, space far enough apart to provide good air circulation around the plants. Maintain a healthy plant through proper fertilization and watering. Keep the leaves dry.  Avoid watering from overhead, instead water just the soil around the plants. Water early in the day so the sun will dry foliage quickly. Remove and destroy all infected plant parts. Select a fungicide labeled for black spot on roses and apply according to the label.  (In Minnesota, preventative spraying normally begins in June or if symptoms are noticed.) If you would like to minimize your use of chemical pesticides, you can try spraying your roses with the following baking soda solution weekly.  Mix one tablespoon of baking soda with a gallon of water and a few drops of a lightweight horticultural oil.  This solution works best as a preventative, rather than as a cure.