Powdery mildew disease  on a rose leaf, Anne of Green Gardens

Some plant diseases are easy to spot, while others are trickier to diagnose. Learn what to do if you aren’t sure what’s wrong with your plant.

Plant Disease Causes

Many plant diseases are difficult to diagnose unless you are an expert. Plant diseases are caused by bacteria, fungus, viruses and other pathogens. However, sometimes plant problems that look like a disease happen when gardeners overwater. Read Gardening 101 Watering to see if this could be the problem.You can also read about other kinds of problems that affect plants like nutrient deficiencies and mechanical damage in “Other Problems.”

Diagnosing the Problem

It’s helpful to know the name of the plant that you suspect has a disease. This is easy in a fruit and vegetable garden, but difficult for landscape plants if you don’t have a plant tag. Take a good-sized sample of the plant in to a local nursery or Cooperative Extension Office/Master Gardener Program for ID of both the plant and the possible disease. Also, some Cooperative Extension offices have websites with helpful photos to help diagnose possible diseases.

Controlling Plant Diseases

If a plant in your landscape has an identified disease that can’t be controlled, consider replacing it with a less susceptible plant cultivar. (A cultivar is a plant cultivated by horticulturalists for characteristics like disease resistance.) For example, some kinds of crape myrtle often get powdery mildew, but cultivars like ‘Hopi,’ ‘Pecos’ and ‘Regal Red’ are resistant. Ask about disease resistant cultivars at your local nursery or gardening center.