The disease known as black spot has probably done more to discourage potential rose gardeners than any other factor. Left untreated, it can  completely defoliate a rose bush by midsummer.  Focus on prevention by beginning a treatment program early in the season.

This fungal disease is caused by the pathogen Marssonina rosae or its sexual stage which goes by the name of Diplocarpon rosae. It is a two cell spore that is not visible without the aid of a microscope. This disease is characterized by black irregular lesions appearing to be on the leaf surface, however occuring under the surface of the leaf. The lower leaves are almost always the first to be infected unless the cultivar is in close proximity to a structure such as the wall of a house or a trellis, in which case the upper leaves can show first infection. These spores over-winter in infected leaves, canes, or on rough surfaces. They do not over-winter in the soil. These spores have no means of self propulsion and are not dispersed by the wind. Splashing water, resulting from rainfall or sprinklers, generally provides a means of transportation for the spore, however it is thought that some spores can hitch a ride on the back of a sticky insect.

Rose FloraTM controls black spot organically.  It contains a bacteria that destroys the black spot fungus, it will also control powdery mildew.  Rose Flora also provides the many other benefits associated with Mity Gro including suppression of many other fungii (pythium, fusarim, phytophtora, verticullium....), balanced soil, better nutrient availablity and improved overall plant health.  We recommend using it with Wilt Pruf which acts as a sticker/spreader and provides some additional defense via the protective barrier it forms on the foliage.

Rose Flora 124 gram dry powder for 45 gallons of application liquid, treat up to 100 roses for season  $39.95

(In addition, we recommend ordering 1 gal Wilt Pruf concentrate for best results)

Natural Rose Success I disease control kit for up to 15 roses,  includes Rose Flora for 12 gallons, 1 quart Wilt Pruf Concentrate and reprint of article that appeared in Annual of ARS, save 23% over cost of iterms purchased separately.  $34.95                                                 

More information on  non-toxic treatment and selection of resistant varieties of roses is available at rose black spot article.

More information regarding treatment is available at Rose Flora.

Application instructions are available at Application Notes.

Information regarding toxicity of fungicides is available at Ask the Experts-Lethal Dose Chart.