Tomato Diseases: Foliage

The old adage, “An ounce of prevention is worth a pound of cure” holds true in all areas of life and in tomato growing.

Healthy plants will produce more fruit and feed you better.

So, knowing what you might expect in the way of diseases that may affect your tomato plants before you get started will save effort in treating diseases later.

You can always get information that is specific to diseases that may be specific to your area and suggestions for growing varieties which are resistant to diseases and are most appropriate to growing conditions in your area by consulting your Cooperative Extension Service.

Disease Symptoms Management
Early Blightfungus Alternaria solani
  • May affect leaves, stems and fruit.
  • Dark spots with concentric rings appearing on older leaves first.
  • Affect leaves may die prematurely
  • Overwinters in plant residue and is soil-borne.
  • Remove affected plants and do a thorough cleaning of debris in the fall.
  • Copper and/or sulfur sprays can prevent further development of the fungus.
Gray Leaf Spotfungus Stemphylium lycopersici
  • Affects leaves only beginning with oldest leaves.
  • Small dark spots on both top and bottoms of leaves. Spots enlarge, turn grayish brown.
  • Centers eventually crack and fall out.
  • Fruit production inhibited.
  • Worse in when weather is warm and moist.
  • Remove affected plants and all debris in fall.
  • Select resistant varieties.
Late Blightfungus-like oomycete pathogen Phytophthora infestans
  • Affects both leaves and fruit of tomatoes.
  • Same disease as responsible for Irish Potato Famine.
  • Resistant varieties: Mountain Magic and Plum Regal.
  • Copper sprays offer some control.
  • Fungus can overwinter in frost free areas
  • Can spread to potatoes, remove debris and don’t save seed potatoes.
Septoria Leaf Spotfungus Septoria lycopersici
  • Papery patches on leaves develop tiny, dark specks inside them.
  • Older leaves affected first.
  • Copper sprays somewhat effective at stopping the spread of symptoms.
  • Fungicides registered for use on tomatoes such as: maneb, mancozeb, chlorothalonil, and benomyl
Southern Blightfungus, Sclerotium rolfsii
  • White mold growing on the stem near the soil line.
  • Dark, round spots appear on lower stem.
  • Girdles the stem and prevents plant from taking up water and nutrients.
  • Difficult to control.
  • Fungus must colonize organic debris near soil surface so removal of debris or incorporation into soil to discourage fungal growth.
  • Contact local county extension for current information.
Verticillium Wiltfungus Verticilliurn albo-atrum
  • Tomato plants seldom wilt.
  • Yellow blotches appear on lower leaves.
  • Then brown veins appear and finally chocolate brown dead sopts.
  • Plant one or more of the many Verticillium-tolerant tomato cultivars.

The seven most common diseases of tomatoes have been assigned a single letter, they are:

  • verticillium wilt (V),
  • nematode (N),
  • fusarium wilt–F1 race 1 and F2 race 2–(F),
  • tobacco mosaic virus (T),
  • septoria leafspot (L),
  • stemphylium (St) and
  • alternaria alternata, or crown wilt disease (A)

Tomato plants have been developed that are resistant to some diseases and are labeled to identify that resistance. For example, a Big Beef tomato labeled VFNT would be resistant to verticillium wilt, fusarium wilt, nematode and tobacco mosaic virus.