Diseases and Abiotic Problems of Greenhouse Tomatoes
Greenhouse Tomatoes are susceptible to many diseases caused by fungi, bacteria and viruses. They are also plagued by many abiotic problems caused from fertility and environmental problems.
The following key provides a brief description of the most commonly observed symptoms associated with certain diseases. A link immediately to the right of the symptom directs you to an image of a plant for identifying the problem. See Extension Publication 1861 "Greenhouse Tomatoes: Pest Management in Mississippi" for fungicides that are commonly used by growers to manage fungal and bacterial diseases of greenhouse tomatoes.
Leaves:
Many disease and abiotic conditions can be identified by symptoms on the foliage. Most of the nutrient deficiencies exhibit distinct symptoms that aid in diagnosis. Wilting of foliage usually requires observation of the stem or roots in order to reach an accurate diagnosis.
| Symptom | Disease or Condition |
| Small, chocolate-brown circular spots that first appear in the terminal of the plant.Leaves may become wilted, and as the disease progresses the leaves will become brittle and appear scorched.There may be black streaks on petioles of some leaves.The presence of thrips insects is necessary for virus transmission. | Tomato Spotted Wilt Virus |
| Young tomato plants that are stunted with leaflets that are reduced in size.Leaves become chlorotic in the terminal of the plant and the margins are often cupped upwards.The presence of whiteflies is necessary for virus transmission. | Tomato Yellow Leaf Curl Virus |
| Leaves first become water-soaked, usually at the tip in the form of a V, followed within 24-48 hours by a gray-brown moldy growth on the dead tissue.Masses of fungal spores are easily observed with a hand lens and look like upright clusters of grapes.Clouds of spores can be shaken from the diseased tissue.The fungus consumes the entire leaf and may move into stems causing wilting of above-ground plant parts. | Botrytis Gray Mold |
| Initially, irregular shaped water soaked lesions appear in between the veins.Then the affected areas become light tan and necrotic followed by becoming dark brown in a matter of 2-3 days.The upper part of the plant may exhibit systemic wilting.Affected plants may become completely wilted and die in a matter of days. | Bacterial Canker |
| Light brown, circular lesions that vary in size from about 1/8-3/4 inch in diameter.Lesions will have the appearance of a target with conspicuous concentric circles.May be confused with Early Blight. | Target Spot |
| Dark brown, circular lesions that vary in size from about 1/8-3/4 inch in diameter.Lesions will have the appearance of a target with conspicuous concentric circles.May be confused with Target Spot. | Early Blight |
| Pale green or yellow spots occur on the older leaves first.On the lower leaf surface an olive-green mold can be observed.Spots may coalesce and cause the leaves to wither and drop from the plant.Foliage is usually all that is affected. | Leaf Mold |
| Water-soaked spots of varying sizes appear on leaves which increase in size rapidly and become brown with moldy fungal growth observed on the lower sides of leaves.Petioles may also be affected.Entire plants may become affected and plant death may occur. | Late Blight |
| White patches of fungal growth, Usually on the upper leaf surface, ranging from ¼ inch diameter to complete coverage of the leaf.The fungal growth can be rubbed off with your fingers. | Powdery mildew |
| Small, dark brown to black round lesions form on leaves which may or may not be surrounded by a chlorotic halo. Can be confused with bacterial spot. | Bacterial Speck |
| Brown, circular spots usually less than 3 mm in diameter that generally coalesce on leaves and cause the leaves to take on a scorched appearance.The spots usually develop on the lower leaves and slowly moves up the plant.Can be confused with bacterial speck. | Bacterial Spot |
| Older leaves on plant become yellow around the margins.Yellowing is followed by necrosis and collapse of the leaf tissue.Some plants wilt fast while others may wilt slowly. | Fusarium Root and Crown Rot |
| Older leaves on plant become chlorotic, usually on one side of the plant.There is an increase in the amount of yellowing on the plant and the plant will wilt during the hottest time of day, but then recover overnight.With time, the wilting becomes more extensive on the plant until the plant dies. | Fusarium Wilt |
| Leaves wilt in the top of the plant with no other apparent symptom expression on leaves. Need to look for problems elsewhere on the plant. | Bacterial Canker Timber Rot (White Mold) Botrytis Stem Blight Pythium Root Rot Bacterial Wilt Lack of Water Broken or Injured Stem |
| Young leaves in the top of the plant become pale yellow.Leaf tissue in between the veins becomes chlorotic (yellow) and begins at the base of the leaf and works out toward the tip while the veins remain green.If not corrected, some leaves will become almost completely white.Symptoms of iron deficiency are commonly observed when the roots become waterlogged. | Iron Deficiency |
| Interveinal yellowing of the older leaves on the plant.Sometimes the margins remain green.Symptom progress from the bottom up on the plant. | Magnesium Deficiency |
| Youngest leaves in the very top of the plant turn bright yellow starting at the base and progressing about 1/3 to ½ way toward the leaf tip.Some leaves may curl downward and have some browning of the margins. | Glyphosate Injury |
| Numerous, small whitish blisters form on undersides of leaves following nights of extremely high humidity. | Oedema |
| Lower, older leaves of plant that curl or roll upwards eventually completely closing up. | Physiological Leaf Roll |
| Leaves in the top of the plant become distorted, taking on a finger-like appearance with thickened leaf veins prominent. Symptom similar to 2,4-D herbicide injury. Flowers abort and fruit is not produced. | Carbon Monoxide, Heater Malfunction or other Air Pollutant |
Stems:
Many greenhouse tomato diseases cause symptoms to be displayed in the upper part of the plant when the real problem is occurring on the lower stem part of the plant.Anytime a plant wilts or exhibits foliar symptoms in the top of the plant, a close inspection of the stem should be performed.The following are symptoms that occur on greenhouse tomato stems and their associated diseases or conditions.Notice that some of the diseases are repeated from the foliar section as symptoms may be observed on both foliage and stem tissue.
| Symptom | Disease or Condition |
| Water-soaked lesions develop near nodes where leaf pruning has taken place or from an infected leaf remaining on the plant.The lesion will range from a few inches up to as much as 24 inches in length and usually encircles or girdles the entire stem.Shortly thereafter the upper portion of the plant begins to wilt as the lesion interrupts water transport.Masses of grayish-brown spores may be present in the diseased area. This disease may initially be confused with timber rot (white mold). | Botrytis Gray Mold |
| Water-soaked lesions appear on lower stem, usually within 2 feet of the soil line.The lesions will first be dark green in color and white mycelium may be present, especially under high moisture conditions.With age, lesions become light brown to tan in color and range in size from about 3 inches up to 8 inches in length.Plant will wilt as the fungus invades the water conducting tissue.Diagnostic, black tubular-shaped sclerotia are formed inside the stem in later stages of disease progression.Infected plants usually die. | Timber Rot (White Mold) |
| Stems may or may not show external discoloration with the formation of adventitious roots mainly at the nodes.Stem cankers are often absent.Plant will exhibit systemic wilting.Longitudinal cut into stem reveals vascular discoloration. | Bacterial Canker |
| Dark brown stem lesions occasionally formed that are elongated with distinct concentric rings.May be confused with Target Spot. | Early Blight |
| Dark brown stem lesions occasionally formed that are elongated with distinct concentric rings.May be confused with Early Blight. | Target Spot |
| Appearance of adventitious roots are more pronounced than that of Bacterial Canker.A rapid wilt of the plant occurs.Vascular tissue will be brown in longitudinal section.Entire pith and cortex may become discolored in later stages of disease development.Diagnostic feature to distinguish between other vascular diseases is the presence of heavy bacterial streaming from a cut stem placed in water. | Bacterial Wilt |
| Formation of a broad, necrotic lesion on the stem that extends just a few inches above the soil line.Refer back to foliar symptoms for additional diagnostic features.Resistant varieties exist. | Fusarium Root and Crown Rot |
| Seedlings may be stunted.Vascular tissue of older plants will be dark brown while the pith remains green.The vascular discoloration extends quite far up the stem which helps differentiate this disease from Fusarium Crown Rot.Resistant varieties exist. | Fusarium Wilt |
| The pith inside the stem disintegrates leaving a hollow stem.Many times a water-soaked lesion occurs on stems.Vascular discoloration does not extend beyond the lesion. | Bacterial Stem Rot |
Fruit:
Tomato fruit exhibit symptoms that aid in diagnosing many diseases and disorders.Many times fruit are near maturity or even ripe when symptoms are most pronounced.The following key provides some of more common fruit symptoms and the diseases and disorders associated with those symptoms.
| Symptom | Disease or Condition |
| Symptoms first appear on ripe fruit as small circular sunken lesions.Lesions enlarge and become more sunken and have small black dots arranged in concentric circles.Sometimes there is a split in the skin of the fruit in the lesion area. | Anthracnose |
| The appearance of small white circular spots or halos on the fruit surface. | Ghost Spot (Botrytis Gray Mold) |
| Fruit with soft rotted appearance with white moldy fungal growth on split and exposed surfaces. | Botrytis Gray Mold |
| Dark, sunken brown spot on fruit which develop into larger circular lesions which often have cracked skin. | Target Spot |
| Fruit breaks down into a watery rot very rapidly and usually has white fungal growth with sclerotia embedded. | Timber Rot (White Mold) |
| Minute lesions that are gray in color and slightly raised and scabby in appearance and often with a dark green halo. | Bacterial Speck |
| Lesions or spots on fruit larger than those of bacterial speck.Spots raised or slightly sunken. | Bacterial Spot |
| Fruit with uneven, blotchy ripening.Fruit often with ringspots or with bumpy flesh. | Tomato Spotted Wilt Virus |
| Fruit with large brown sunken tissue at flower end. | Blossom-End Rot |
| Fruit close to the growing medium with alternating light and dark brown rings. | Buckeye Rot |
| Fruit with scars, russetting, cracks, yellow or green shoulder, and zippering. | Various Physiological Conditions |
| Fruit with large, malformed open locules with exposed seed. | Poor Pollination |
Publications
News
RAYMOND, Miss. -- Current and prospective greenhouse vegetable growers can learn about the specialized production method during Mississippi State University’s 2024 Greenhouse Vegetable Short Course on Feb. 27-28. The course will be held at the North Mississippi Research and Extension Center’s Magnolia Building in Verona from 8 a.m. to 5 p.m. each day. It is open to greenhouse vegetable producers throughout the Southeast.
STARKVILLE, Miss. -- Vegetable growers soon will have two chances to learn about managing pests on produce in greenhouses and high tunnels.
There’s nothing more satisfying than homegrown tomatoes. You don’t have to be a gardening expert to grow delicious tomatoes in your backyard. Here are a few tips that will help you grow the best looking (and tasting) tomatoes out there: