Tomato Plant Diseases

Kathleen Roberts
Early Blight

Though rarely fatal to the plant, tomato plant diseases are extremely frustrating to gardeners who are anticipating fresh, delicious tomatoes. For many, home-grown tomatoes are the highlight of summer, so getting diseased fruit is a huge disappointment.

About Tomato Diseases

Most tomato diseases are cause by the weather. Damp, cool conditions frequently cause problems for tomatoes because they tend to prefer the hot temperatures of summer in rich, well-drained soils.

While there are many diseases that can impact tomato plants, you will find that only a few will be relevant to you. Certain diseases are more prevalent in specific areas. To learn which ones are a problem where you live, check with your county Extension Service. They know which diseases are common for the tomato plants where you live. Armed with this knowledge, you can select varieties that are resistant to those particular diseases. Typically, the Extension Service can tell you which varieties do best in your local. They should always be your first stop when you need information about what will grow where you live.

A List of Tomato Plant Diseases

The following chart shows just a few common diseases that afflict tomato plants. It will also tell you how to recognize the disease, what steps can be taken to control it and what parts of the plant are affected by the disease. Use this key when identifying the plant parts affected: G= Green Fruit, R= Ripe Fruit, L= Leaf, S= Stem and Rt= Roots.

More Help

Because this is only a short list of the numerous tomato plant diseases you may have to deal with, you may want to learn about some that are not listed, or see images to help you identify them. The Tomato Problem Solver for more in-depth information.

Tomato Plant Diseases
Disease Plant Part Affected Symptoms Control
Alternaria Canker G, R, L, S Brown and black lesions on plant; Grayish spots on fruit Destroy plant matter at end of season; Use care not to damage plants, cut can provide an entry for disease; Use drip irrigation as opposed to sprinkler
Anthracnose R Round, sunken spots, dark in the middle; may have "bullseye" appearance Fungus is spread by water splashing on fruit; Use drip irrigation; Fungicides; Rotate crops
Bacterial Canker G, L Wilting leaves; Dried up leaves on plants;Brown, brown/yellow spots; Yellow slime on stems Bacteria is soil or seed borne so soil should be sterilized; Rotate crops; Handle plants with care, damage allows bacteria to enter
Bacterial Speck G, L Small, dark brown spots with yellow circle around them Increased by wetness on plant so use drip irrigation; Copper spray
Bacterial Spot G, L Dark brown, watery spots on leaves, later becomes black and falls out; Black raised spots on fruit later scab over Copper spray; Weed control, keep the garden clean
Blossom End Rot G, R Blossom end has a watery look, later turns sunken and black This is a calcium deficiency caused by water stress;Regular irrigation; Mulch; Calcium or lime in soil before planting; Liquid fertilizer with calcium nitrate
Buckeye Rot G, R Rounded light and dark brown circular lesion; May look water soaked or leathery Stake plants up off the ground; Plastic mulch to protect from wet soil
Cloudy Spot R Patches of yellow and white flecks; Flesh looks white and corky Insecticide to control stink bugs which are the cause
Cucumber Mosaic Virus L Stunted plants with small leaves;Mottled leaves; Small, oddly shaped fruit Control aphids; Remove weeds; Remove infected plants immediately
Cottony Leak R Large, water soaked areas; Darker or lighter areas; Easily punctured when handled Stake plants to keep fruit off the ground; Use drip irrigation to prevent wetting of plants
Damping Off Rt Multiple diseases that cause seedling to die; Watery lesions on stem near soil Sterile seed bed; Use clean seed-starting equipment; Avoid overwatering and overcrowding
Early Blight R, L, S Sunken, dark lesions near stem; Oddly shaped brown lesions surrounded with yellow on leaves Drip irrigation; Fungicide spray; Rotate crops
Fusarium Wilt S Leaves or branches wilt, turn yellow, then brown; Dead branches or leaves may stay on plant; Brown discoloration in branches Select resistant varieties
Gray Leaf Spot L Brown/black specks on underside of leaves that become holes; May be yellow around spots; Leaves may turn yellow and drop Control weeds; Drip irrigation; Fungicides
Late Blight G, L, S Water soaked areas on leaves; Spots turn brown, papery; Green/brown, greasy looking, rough lesions on fruit; Green or black stem lesions Fungicide during cold, wet weather
Leaf Miner L Squiggly trail in leaves caused by leaf miner larvae Insecticide for leaf miners
Leaf Mold L Light green spots on older leaves; Under leaves have purple or olive colored mold; Yellow leaves drop from plant Fungicides
Tomato Plant Diseases