Tomato Fungus

Tomato fungus may be one of many common fungi that plague tomato gardeners. Fungus can arrive on young transplants purchased from the big growers, or it can be a leftover in the soil from the previous year's problem.

Fortunately, there are positive steps you can take to control and prevent tomato fungus problems. There are some differences in control methods for the many pathogens, but also good general gardening practices that are always recommended.

How to Identify Tomato Fungus

Gray Leaf Spot
Clemson University
USDA Cooperative Extension Slide Series,
Septoria Leaf Spot
Paul Bachi, University of Kentucky
Research & Education Center,
  • A fungus can attack both seedlings in the greenhouse and mature plants in the garden.
  • In seedlings a fungus can cause stunting, yellowing, and premature loss of cotyledons (seed leaves).
  • In advanced cases the fungus causes root rot, wilting, and seedling death.
  • In advanced cases the fungus causes root rot, wilting, and seedling death.


  • Easily spread by splashing water.
  • Fungus survives between seasons on infected plant debris.
  • Extended periods of leaf wetness, high humidity, and warm temperatures exacerbate the development and spread of diseases.

Preventative Measures

  • Plant only high quality transplants, discarding any that show any sign of disease or stress.
  • Practice crop rotation on a three-year cycle with non-hosts.
  • Remove crop debris, volunteer tomato plants, and weeds that can host the disease.
  • Avoid wetting the leaves when possible by watering the base of the plant.
  • Don't start seeds in garden soil -- use soilless mix instead. (See Growing tomatoes from seed for more information).


Natural remedies

  • Remove and destroy infected plants.
  • Add more organic matter to your soil for tomatoes before planting.

Chemical treatments

  • If fungal diseases are a recurring problem in your garden, consider using copper-based fungicides when fruit first develops.
  • Begin treatments as soon as you notice the problem and spray all plant surfaces.

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