Ornamental & Tree Diseases

Plant Disease Dispatch Sheets
September 29, 1997

M-319 - Die-back and Stem Canker of Rose

There are many different diseases that attack roses in Mississippi. These will vary in type and severity depending upon location and weather conditions. Die-back and stem canker are really a complex of diseases since they are caused by several different types of fungi. However, identifying these stem canker diseases is not of great importance since the control is very much the same for all. This disease is usually more prevalent on plants that have been severely defoliated by black spot or are under some type of stress due to poor cultural practices. The die-back phase of the disease appears as a black sunken lesion that causes death of the terminal areas of the cane. The die-back phase become established through injuries, leaf scars, petal scars or any type of wounds that occur on the young, tender canes. Stem or cane cankers are large, girdling type of lesions that appear on the more mature canes. These will vary in color from yellow to tan, or dark brown to black. The bark of the canes may be split and sprinkled with raised, black specks which are the fruiting structure of the fungus. Severely infected canes may be girdled and die back.

There are several steps that need to be followed in controlling this or any disease of rose. First of all, buy only best quality disease-free plants from a reputable nurseryman. Space plants for good air circulation. Keep roses mulched throughout the growing season. Collect and burn all leaves in the autumn. Prune the plant properly in the fall or spring according to the type and variety. When pruning, be sure to dip or swab tools between cuts in 70% denatured alcohol (rubbing alcohol) or liquid household bleach diluted to one part bleach to four parts of water. Use a pruning paint to protect the pruned areas. Spray regularly for the control of leaf spot and canker. Since the fungi responsible for canker overwinters in the canker, careful pruning is very important.

The fungicides that are effective in controlling black spot will also control die-back and canker. A regular spray program throughout the growing season is advisable. You may use one of several fungicides, including maneb (Manzate, Dithane M-45), benomyl, chlorothalonil (Daconil 2787 and other fungicides containing chlorothalonil as the active ingredient), or triforine (Funginex). All give good control if applied according to label directions through the growing season. Regular spraying and thorough coverage are important for control. Start spray program at first signs of growth in the spring.