How can I control blackspot on my roses?

Question: 

How can I control blackspot on my roses?

Answer: 

Blackspot is a common fungal disease of roses.  Symptoms of blackspot are circular black spots on the leaves.  Infected leaves turn yellow and drop prematurely.  Initially, symptoms develop on the lower leaves and gradually move upward.  By late summer, severely infected plants may be nearly defoliated. 

The blackspot fungus overwinters on fallen leaves and infected canes.  Spores are splashed onto newly emerging foliage in spring.  Blackspot development is favored by warm, wet weather. 

Careful rose selection, cultural practices, and fungicide treatments can be used to control blackspot on roses.  Rose varieties differ widely in their susceptibility to blackspot.  When purchasing roses, select rose varieties that are resistant to blackspot.  When selecting a planting site, choose a site that receives full sun and provides good air movement.  Full sun and good air movement promote drying of rose foliage and discourage blackspot infections.  Reduce the amount of overwintering fungi by carefully cleaning up the leaf debris in fall.  When watering roses, apply water directly to the ground around the plants.  Do not wet the foliage.  Fungicide applications must begin at the first sign of disease symptoms. 

Learn more about growing roses in this article: Growing Roses in Iowa.

Category: 

Links to this article are strongly encouraged, and this article may be republished without further permission if published as written and if credit is given to the author, Horticulture and Home Pest News, and Iowa State University Extension and Outreach. If this article is to be used in any other manner, permission from the author is required. This article was originally published on . The information contained within may not be the most current and accurate depending on when it is accessed.