Q&A: Disease Diagnosis

A: There are many books on the market that can help you identify plant diseases. The best books provide descriptive text with color pictures.

Also consider your area's cooperative extension service, which may have a master gardener on hand, and your favorite nursery as resources. Provide a proper sample by collecting a few leaves or a small cutting from the affected portion of the plant. Seal the sample in a plastic bag and take it to your extension service or nursery. Be prepared to answer several questions: Is the plant growing in sun or shade? What type of soil do you have? How and when do you water? Is there good air circulation around the plant?

When you take a diseased sample to the nursery, don't open the bag on your own--you could contaminate nursery stock. Instead, wait for the extension agent or nursery worker to choose a safe location and open the bag there.

--Paul James, master gardener and host of Gardening by the Yard