Latin name: Diplocarpon rosae
Common name: Black Spot
Plant family: Rose
Date/Location of specimen: http://i0.wp.com/ugaurbanag.com/wp-content/uploads/2015/09/black-spot.jpg
Description: Black spot is one of the most common and important diseases of roses throughout the world. It is caused by the fungus Diplocarpon rosae. Black spot will cause a general weakening of the plant so that progressively fewer and fewer blooms are formed if the disease is left unchecked. Plants so weakened are increasingly subject to winter injury. As the name implies, infected leaves show black spots especially on the upper leaf surface. The spots can be up to 1/2 inch in diameter and typically have fringed borders. Yellowing of the leaf begins surrounding the spots and the entire leaf may yellow and eventually drop off. 1
The fungus produces spores in the black spot lesions on the upper leaf surface and these spread in water to initiate new infections. Wet conditions are required for the disease to build up … The fungus spends the winter in resting structures on fallen leaves and also in dormant infections on young stems and buds, producing spores in the spring to infect young foliage. 2
Control: Remove leaves from the ground and prune canes that have lesions to reduce overwintering of the disease.
References:
1 http://extension.umaine.edu/ipm/ipddl/publications/5097e/
2 https://www.rhs.org.uk/advice/profile?PID=270
3 http://ugaurbanag.com/2011/09/black-spot-on-roses/
Collection Sample #4 of 5 DISEASES
Master Gardener Class Horticulture Portfolio
