University of Maryland Extension University of Maryland

College of Agriculture & Natural Resources

Plant Diseases

Plant diseases involve profound physiological and morphological changes that cause a disruption of normal plant function over time.  Disease symptoms might include: wilting, necrosis, abnormal coloration, defoliation, fruit drop, abnormal cellular growth, cankers, galls and/or stunting. Click on a topic or photo below (or use the left menu) to learn more about common bacterial, environmental, fungal and viral plant diseases in Maryland.

Note:  Not all plant problems are caused by disease organisms.  Look for other factors that may be the primary cause for symptoms to appear. For example: poor planting, too much mulch, compacted soil, too much shade, too much moisture, etc.

Click here for Common Diseases of Trees and Shrubs.

fire blight ozone damage on leaf
rose rosette

Note that different diseases can cause similar symptoms on the same plant.  Also remember that damage caused by insect or mite feeding or environmental conditions can cause “disease-like” symptoms on plants.

People who encounter plant diseases usually want to know the best control measures. Unfortunately, by the time the disease symptoms appear, it is often too late to reverse the damage caused by the disease agent. In some cases there are no acceptable control measures available short of plant removal. Diagnosis of the disease can allow planning for a control method to prevent the disease next season. The various controls for diseases include exclusion strategies, inoculum reduction methods, chemical controls, biological controls, resistant plants, and integrated pest management (IPM) strategies, which may utilize any or all of these methods.

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IET Departmentof the College of Agriculture and Natural Resources. © 2015.