Black Spot Plant Disease

Black Spot Plant Disease image by iastate.edu
Black Spot Plant Disease image by iastate.edu

Overview

Roses and other garden plants can suffer from any of a number of fungal diseases. Black spot is one of the most common and most devastating diseases for gardens in humid or rainy climates.

Symptoms

Black spot disease appears on plants' leaves as circular black patches with irregular edges. Members of the rose family are the most common victims. Eventually, the entire plant droops and sheds dead leaves.

Cause

This disease is caused most often by the fungus Diplocarpon rosae. The fungus survives through the winter in dead foliage and its spores are splashed onto healthy plants during spring rain storms, thus spreading the disease.

Significance

Black spot disease is not merely unattractive. The infection's steady progression upward along a plant's stalk eventually kills its host.

Treatment

Regular spraying with a fungicidal preparation or applications of wettable sulfur are the only known treatments for black spot to date. Removing diseased plants is regarded as a more effective solution.

Prevention/Solution

Commercial growers regard prevention through good garden hygiene as the best method of preventing black spot. Destroying diseased plants and cleaning up dead leaves from the growing area are effective preventative steps.

References

  • Treating black spot

Who Can Help

  • Ohio State University Extension

About this Author

Susan Kerr has been a professional writer since 1992. She is the former managing editor of "Pennsylvania Business Central" and "State College Magazine," and is now a contributor to several Faircount Media publications such as "The Year in Veterans Affairs and Military Medicine." Kerr holds a Bachelor of Science in organizational leadership from St. Francis University.

Photo by: iastate.edu