How to Determine a Tomato Plant Disease


Like all garden plants, tomato plants often contract and suffer from various plant diseases and disorders. Although certain disorders simply cause an unsightly appearance in tomatoes, many diseases affect the production of fruit, and may result in the death of one or more tomato plants. Proper preventative measures, as well as quick responses in providing treatments, supply tomato plants with the necessary elements to reach maturity and produce an abundant harvest.

Step 1

Examine the leaves on your tomato plant. Notice any spots on multiple leaves. Notice the size and color of the spots on your tomato plant.

Step 2

Look for brown spots with light centers. Septoria leaf spot disease causes circular spots with grayish white centers and darker edges. Protect your tomato plant's leaves from splashing rain and faucet water to avoid and eliminate the development of this type of mildew disease.

Step 3

Check for spots on the lower leaves of your tomato plant. Notice any brown to black spots containing dark edges. Merging spots may form irregular shaped blotches. Another type of damaging fungus, early blight causes the appearance of these leaf spots. Correct this condition by providing extra space between individual tomato plants. Allow at least a few inches between mature tomato plants for adequate airflow.

Step 4

Look near the stem on ripening fruit. Notice any cracks appearing by the stem. Cracking fruit indicates a lack of sufficient moisture in the soil during the ripening stage. Dry periods followed by excessive moisture create heavy cracking. Minimize this condition by providing regular amounts of water to the soil near the roots of your developing tomatoes. Keep the soil slightly moist at the level of the plant's roots.

Step 5

Examine developing fruit for the appearance of small spots. Notice any tiny, raised spots, which indicate the presence of bacterial speck. Use a magnifying glass to see these miniscule spots. Look for multiple, raised spots with dark centers on individual fruits. This disease, known as bacterial canker, closely resembles the smaller spots of bacterial speck. Treat both of these bacterial diseases with a product containing copper. Apply the treatment according to the manufacturer's instructions.

Things You'll Need

  • Magnifying glass
  • Copper treatment


  • Clemson University: Tomato Diseases
  • Colorado State University: Recognizing Tomato Problems
  • Iowa State University: Tomato Diseases and Disorders
Keywords: tomato disease, tomato condition, tomato disorder

About this Author

Laura Dee is a writer, artist, and the co-owner of Wallace & Wallace Copywriting,an online business which specializes in providing marketing materials and copy to various companies. She has written for Demand Studios since 2008 and is currently working on a series of childrens' picture books.