Key to Common Problems of Tomatoes

• Symptoms: light tan or gray blotches.
• This is cold weather injury commonly seen in the early spring when tomatoes, a warm-season crop, experience nighttime temperatures below 35°F. 
• Affected leaves out-grow the injury if plants are healthy and not stressed further by low temperatures.

• Symptoms: small, round gray spots with dark margins develop on the lower leaves, usually when the first fruits begin to form.
• Septoria leaf spot is caused by a fungus, Septoria lycopersici. The pathogen is favored by wet weather. 
• Fungal lesions gradually enlarge, coalesce, and cause leaves to turn yellow and die. Often co-occurs with early blight.

More about septoria leaf spot

• Symptoms: small, irregular brown lesions, often with yellow halos, that enlarge rapidly; a “bull’s-eye” pattern appears within the lesions. Lower leaves are affected first.
• Individual lesions enlarge and coalesce and can kill entire leaves, reducing yields. Can also infect stems and roots.
• This is a fungal disease (caused primarily by Alternaria linariae (syn. A. tomatophila). It can spread in wet and dry weather but is favored by rainy weather. This disease often co-occurs with septoria leaf spot.

More about early blight

• Symptoms: small, dark spots (⅛ inch or less); leaf yellowing; spots coalesce and leaves turn brown and fall off. 
• The two most common bacterial diseases of tomatoes in a home garden are bacterial spot and bacterial speck.
• The bacteria overwinter on crop residue and are seed-borne.

More about bacterial diseases of tomato

• Symptoms: tiny yellow or white spots (stippling); spots can coalesce to cause yellow blotching; leaf undersides may appear dirty.
• Spider mites can be seen on leaf undersides with the naked eye or using a hand lens.
• Spider mites suck chlorophyll from leaf tissues, resulting in yellow discoloration.
• Plants with severe mite damage may be further injured by insecticide sprays (including soaps and oils).

More about spider mites

• Symptoms: lower leaves turn yellow and then brown; leaf and stem wilting with some recovery at night.  
• This is caused by a soilborne fungus, Fusarium oxysporum sp. lycopersici. 
• When the outside of an infected stem is scraped you will see browning of the vascular tissue underneath (internal stem tissue is discolored).
• This is the most common wilt disease of garden tomatoes in Maryland.

More about fusarium wilt

• Symptoms: Leaf undersides and stems appear purple in color.
• This is very common in new tomato seedlings and transplants.
• This is caused by a lack of phosphorus and possibly other stress factors.
• Plants recover when roots are fully established in the garden.

• Symptoms: upward rolling of the leaves.
• This is a common occurrence in mid-summer and is associated with high temperatures and moisture stress. 
• Some tomato varieties, including heavily pruned determinate-type varieties, are more prone to leaf roll.
• It does not harm plant growth or yields.

• Symptoms: leaf curling, distortion, yellowing.
• Aphids are small, soft-bodied insects that may be green, pink, or black, usually found on the young growth of the plant. Check the undersides of the leaves.
• Aphids suck plant sap and excrete sticky honeydew.
• Naturally occurring predators such as ladybird beetles control them.

More about aphids

• Symptoms: leaves curled, twisted, strappy, distorted, stay small in size.
• Usually occurs when weed control spray drifts onto nearby plants. Some herbicides can drift many feet from the site of application. 
• Most common with phenoxy-type herbicides (2,4-D) which are used commonly in lawn and agricultural herbicide applications.

More about herbicide damage

• Symptoms: leaves twisting, curling, distorted, smaller than normal in size; leaves may feel rough, and crinkled.
• Tobacco mosaic virus (TMV) and tomato mosaic virus (ToMV) are two of the more common viruses that affect tomatoes.
• Plant disease-resistant tomato varieties.

More about viruses

• Symptoms: tiny round holes (shot holes) in the leaves.
• Flea beetles (multiple species) are among the earliest emerging insects (late April-early May). They are tiny, 1/10 of an inch, usually shiny black or brown. Adult beetles jump away when disturbed, much like fleas.
• One or two generations per year. Bigger pest problem of potato and eggplant.
• Use row cover fabric or insect mesh over plants from the time of planting until flowering.

More about flea beetles

• Symptoms: leaves are chewed or stripped off of branches.
• This chewing is caused by the caterpillars of the hornworm moth.
• They are a mid to late-summer pest. Remove caterpillars by hand and discard.
• A large percentage is controlled by a wasp parasitoid (natural enemy) 

More about tobacco hornworm

• Symptoms: Small knobs, swellings, or bumps on stems are usually harmless and caused by plant genetics (natural growth) or stressors in the environment.
• No action needs to be taken.

• Symptoms: dark, leathery, sunken areas on the blossom end of the tomato, most prevalent on enlarging fruit.
• Caused by a lack of calcium in cell walls due to environmental stress such as inconsistent or shallow watering and droughty conditions, or excessive use of nitrogen fertilizers. 
• Keep plants well-watered and mulched. Check soil pH and amend accordingly.

More about blossom end rot

• Symptoms: pale-colored, sunken, or blistered areas on tomato fruits exposed to full sun. 
• Most prevalent on plants that have lost foliage due to disease or insect feeding. 
• Causes fruits to be inedible.

More about sunscald

• Symptoms: superficial spots and blotches, white on young fruit or yellow on mature fruit.
• This is feeding damage caused by stink bugs. The nymphs and adults insert their piercing mouthparts and suck plant sap from fruits, leaves, buds, or blossoms of the plant.
• Cloudy spots in the fruit can be cut out. This does not affect eating quality

More about stink bugs

• Symptoms: circular sunken spots with darkened centers, usually on overripe fruits.
• Anthracnose disease is caused by more than a dozen species of fungus in the genus Colletotrichum.
• The fungi overwinter in seeds, soil, and plant residues.
• Pick fruits before they ripen fully.

More about anthracnose

• Symptoms: tomatoes are misshapen, often with deep crevices or holes and scarring in the blossom end.
• This is common in home gardens, most often on the early fruit clusters of large-fruited cultivars.  
• The cause is thought to be exposure to cool temperatures (below 50° F) before or after transplanting.

More about catfacing

• Symptoms: cracks radiating outward or in concentric rings around the top of the fruit; small cracks on the fruit surface.
• This is a common weather-related condition caused by fluctuations in soil moisture, persistent rainfall, and heavy dews.
• Pick fruits before they ripen fully.

More about cracking

• Symptoms: dry, brown scars resembling zippers extend from the stem to the blossom end of fruits. 
• This occurs when flower parts stick to the developing fruit. Cool weather and plant genetics are considered to be contributing factors as well.
• This is superficial and does not affect yields or eating quality.

• Symptoms: lower leaves turn yellow to brown; leaf and stem wilting with some recovery at night.  
• This is caused by a soil-borne fungus, Fusarium oxysporum sp. lycopersici. 
• When the outside of an infected stem is scraped you will see browning of the vascular tissue underneath (internal stem tissue is discolored).
• This is the most common wilt disease of garden tomatoes in Maryland.
• Use resistant varieties, rotate to a new garden area, or grow plants in containers.

More about fusarium wilt

• Symptoms: wilting and the collapse of individual stems or entire plants. Lower stems turn dark brown. 
• Southern blight is caused by the fungus Sclerotium rolfsii, which can infect a wide range of vegetable crops and herbs. 
• White strands of fungal mycelium and small tan, round sclerotia (resembling seeds) may be found at the base of the stem.

More about southern blight