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Tomato Growing Problems: Troubleshooting

Tomato Worm1
Tomato growing problems include the tomato horn worm.
Tomato growing problems include the tomato horn worm.

Tomato plants are susceptible to several diseases and pests. Preventing problems is the best growing strategy.

  • Keep the garden free of weeds that can harbor pests and diseases.
  • Use floating row covers at planting time to exclude early season pests.
  • Prune and train tomatoes early to provide good air circulation.
  • Pick off any leaves that show sign of disease or insect attack.
  • Later, keep an eye on plants as they blossom and set fruit; water evenly and regularly and mulch to conserve soil moisture.
  • At the end of the season get rid of crop residues and cultivate the soil to expose insect larvae.

Best tips on How to Grow Tomatoes.

Here is a troubleshooting list of possible tomato problems with brief control suggestions. For a full description of pests and diseases and prevention and controls click over to the Pest Problem Solver of the Disease Problem Solver. For tomato growing details click to How to Grow Tomatoes.

Here are 35 tomato plant problems and solutions:

Small holes in leaves of seedlings. Flea beetles eat small holes in the leaves of seedlings and small transplants. In worst case, the entire plant is destroyed. Flea beetles usually concentrate on seedlings. Healthy tomatoes can tolerate beetle damage.

Leaves eaten off plant. Colorado potato beetles or vegetable weevils attack many vegetables. They are small and dark colored and do not fly, so they are slow to spread. Hand-pick adult beetles off of plant. Keep garden clean. Use rotenone in severe cases.

Lower leaves have a bronze, oily color. Tomato russet mite is not visible to the eye but you will see them with a hand lens; they are whitish-yellow and pear-shaped. Avoid growing tomatoes near petunias. Treat with sulfur.

Leaves are yellowish and slightly curled with small shiny specks. Aphids are tiny, oval, yellowish to greenish pear-shaped insects that colonize on the undersides of leaves. They leave behind sticky excrement called honeydew which can turn into a black sooty mold. Use insecticidal soap.

Leaves turn yellow and then brown from the bottom up; plant loses vigor. Root knot nematode is a microscopic eelworm that attacks feeder roots. Plant resistant varieties labeled VFN. Rotate crops. Remove old plant debris from garden.

Leaves appear scorched and wilted. Leafhoppers are green, brown, or yellow bugs to ⅓-inch long with wedge-shaped wings. They jump sideways and suck the juices from plants. Use insecticidal soap. Cover plants with floating row covers to exclude leafhoppers.

Water-soaked spots on leaves; spot become circular with gray centers. Leaf spot or Septoria leaf spot is a fungus disease. Plant resistant varieties. Rotate crops. Keep garden free of plant debris. Apply copper dust or liquid copper spray every 7 to 10 days.

Tiny white winged insects around plants. Whiteflies will congregate on the undersides of leaves and fly up when disturbed. Introduce beneficial insects into the garden.

Trails and tunnels in leaves. The leafminer larvae tunnel inside leaves. Destroy infected leaves and cultivate the garden to destroy larvae and keep adult flies from laying eggs. Cover crops with floating row covers.

Young plants are cut off at the ground. Cutworms can be found at the base of plants, they are small curled grayish grubs. Handpick and destroy cutworms and place a cardboard collar around young plants.

Leaf veins turn purple and leaves curl downward. Curly top virus is spread by leafhoppers. The leaves will become thick and leathery or brittle and the plant stops growing. Once the virus hits lift and throw away the plants. Control leafhoppers.

Leaves turn purple. There is a phosphorus deficiency in the soil. The leaves may also be bluish-green, bronzed, or reddish along the veins and margins. Add phosphorus rich bonemeal to the soil.

Leaves have an irregular light and dark green pattern leaves are narrow and wrinkled. Tobacco mosaic virus can be spread by tobacco plants and smoking. There is no cure for the virus. Plant resistant varieties (TMV on label). Infected plants can produce edible fruit but the size and yield is reduced.

Plants produce a lot of lush foliage, but little or no fruit. Several possible causes: (1) too much nitrogen in soil: use a phosphorus rich fertilizer; avoid too much nitrogen; (2) overwatering: allow the soil to dry to a depth of 4 inches before watering again; (3) temperatures are too low: cover plants with plastic covers; (4) inadequate pollination: lightly tap plants at flowering time to increase pollination.

Blossoms fall off. There are several possible reasons: (1) night temperatures are too low, less than 55°F (13°C): use a hormone spray to improve fruit set during low temperatures and keep soil evenly moist; (2) day temperatures are too high, greater than 90°F (32°C): there is no solution, temperatures must drop; (3) smog during blossoming period: tap on blossoms 3 times a week when flowers are open to assist pollination; (4) too much nitrogen in the soil: feed plants properly; (5) too much shade: plant tomatoes in full sun; (6) early blossoming: don’t plant too early, early blossoms will not set fruit; (7) the variety is not adapted to your region: get regional suggestions from a garden center or the cooperative extension.

Lower leaves yellow, tiny brown specks on leaves. Smog or air pollution. Some tomatoes grow poorly where the air to polluted.

Plants turn pale yellow with brown lesions on leaves, brown stripes on stems. Spotted wilt virus is spread by thrips. You may seed circular light areas or bumps on fruit. The plant will eventually die. Remove and destroy infected plants. Keep weeds down; they host thrips.

Plant yellows beginning on one side or branch, yellowing spreads; plant wilts. Fusarium wilt is a soil fungus that infects only tomatoes, usually where the soil is warm. If you cut the plant at the base, the main stem will be dark reddish brown instead of ivory color. Grow resistant varieties (F or VF).

Older leaves yellow and die; yellowing begins between main veins of leaves. Verticillium wilt is caused by a soil fungus. It favors cool soil and air temperatures. Grow resistant varieties (V or VF) and avoid planting where tomatoes, potatoes, peppers, eggplant, and cucumber family plants have been recently growing. This disease is most evident in hot weather when the plant is loaded with fruit and water is short.

Plants are slow growing and wilt; roots look water-soaked or brown and dry. Phytopthora root rot is caused by a soil fungus. This disease is common in heavy, clay soils. Keep the watering short and add organic matter to the planting bed.

Cottony white growth on stem near soil line, plant wilts. Southern blight is caused by a fungus. Southern blight gets its name because it spreads rapidly in humid weather in temperatures greater than 85°F. The fungus feeds on decaying organic matter. Keep the garden clean of plant debris. Lift and destroy infected plants. Rotate crops.

Fruit turns light brown and leathery on side exposed to sun. Sunscald is caused by over exposure to the sun. don’t prune away foliage above fruit clusters.

Leaves and stems look water soaked and a grayish fungus grows on the undersides of leaves. Late blight is caused by a fungus which favors high humidity and temperatures around 68°F (20°F). Keep the garden free of plant debris and avoid overhead irrigation.

Round white powdery spots and coating on leaves. Powdery mildew is caused by fungal spores. Spores germinate on dry leaf surfaces when the humidity is high; spores do not germinate on wet leaves. Common in late summer or fall but does not result in loss of plant. Avoid water stress. Pick off infected leaves.

Dark brown to black blotches surrounded by yellowing along edges of leaves. Bacterial speck develops where the weather is wet and cool, less than 70°F (21°C). Delay planting until temperatures warm. Rotate crops and avoid overhead watering.

Worm in immature or ripe tomato fruit. Tomato fruitworm (corn earworm) is a pale caterpillar with a brown head about 1¾ inches (4.5 cm) long; it is the larvae of a night-flying moth with brownish or olive wings. Bacillus thuringiensis can be used to control worms, but control is difficult unless the infestation is severe. This tomato fruitworm is also known as the corn earworm.

Dark, leathery areas appear on the blossom end of fruit. Blossom end rot is caused when there is too little moisture in the soil, particularly when temperatures are greater than 90°F. Sometimes there is a calcium deficiency in the soil which keeps roots from taking up water. Mulch planting beds to keep soil moisture even; water regularly. Test soil for calcium deficiency.

Fruit is cracked radially from top toward the bottom of the fruit. Cracking is caused by uneven soil moisture–the soil is either too wet or too dry. This often occurs when temperatures are greater than 85°F. Allow foliage to shade fruits below. Mulch to keep soil moisture even. Water thoroughly and then allow the soil to dry to a depth of 4 inches and then water again.

Brown dashed scar or zipper streak appears on side of fruit. Zipper-like scars appear after blossoms stick to tiny fruit when the weather is too wet and cool at flowering time. Pull flowers off of fruit when the fruit is very small.

Fruit is misshapen and distorted. This happens when the plant is exposed to temperatures below 55°F at the time of blossoming. Keep tomatoes warm with cloches or row covers early in the season. Plant later after temperatures have warmed. Grow early lower temperature varieties: Early Girl, Rocket, Earliana.

Small worm tunneling in fruit. Potato tuberworm is 3/8 inches (9.5 mm) long caterpillar the larvae of a moth that frequents potatoes. Avoid planting tomatoes where potatoes where planted the year before. Destroy potato plant debris.

Small worms tunnels into fruit. Tomato pinworm is a very small leafmining caterpillar about ¼-inch (6mm) long that tunnels into tomato fruit. It leaves a small entry hole which allows disease to enter the fruit. Remove and destroy tunneled leaves. If fruit is attacked it must be thrown away. Keep garden clean of plant debris and weeds where pinworms overwinter.

Leaves eaten, small to large holes eaten in fruit. The hornworm is a green caterpillar from 3 to 5 inches long with white stripes and a horn on its rear end. It is the larvae of a mottled gray or brown moth with orange spots. Hand pick and destroy hornworms. Use Bacillus thuringiensis and parasitic wasps.

Fruit surface is eaten or fruit is hollowed out. Snails feed on the surface of fruit. Slugs hollow out the fruit. Keep tomatoes off the ground. Set out beer traps for snails and slugs.

Cloudy cream or yellowish colored spots without definite margins on ripe fruit and the tissue underneath is spongy. Stink bugs are gray or green shield-shaped bugs about ¼-inch long; they feed on fruits. Remove garden debris and weeds where bugs can overwinter. Hand-pick egg masses and bugs and destroy.

Sunken water-soaked areas on fruit; fruit shrivels and become watery. Anthracnose and alternaria fruit rot are fungal diseases that causes dark, brown, or black sunken, circular spots on stems, leaves, and fruits. Keep fruit off the ground and destroy rotting fruit. Rotate crops.

Fruits are malformed with ugly scarring. Catfacing is caused by cool and cloudy weather at the time of blossoming. Weather causes blossoms to stick to small fruits and create distortions. Pull blossoms off of fruit when the fruit is still small. Plant varieties that resist catfacing, Big Set and Burpee’s VF.

Best tips on How to Grow Tomatoes.

Written by Stephen Albert

Stephen Albert is a horticulturist, master gardener, and certified nurseryman who has taught at the University of California for more than 25 years. He holds graduate degrees from the University of California and the University of Iowa. His books include Vegetable Garden Grower’s Guide, Vegetable Garden Almanac & Planner, Tomato Grower’s Answer Book, and Kitchen Garden Grower’s Guide. His Vegetable Garden Grower’s Masterclass is available online. Harvesttotable.com has more than 10 million visitors each year.

Comments

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    • What you describe sounds like the appearance of adventitious roots that erupt from the main stems of tomato plants infected with tomato pith necrosis which is a bacterial infection. There is no treatment, only prevention. Pith necrosis is caused by too much nitrogen in the soil. Other causes include cool nighttime temperatures and low humidity. Avoid excessive use of nitrogen.

  1. my cherry tomatoes start to ripen, turn orange and then drop off. They are soft and mushy inside. I pulled a few orange ones off the vine to ripen on window sill, but they cracked open and were mushy. No black spots on leaves or fruit, but some leaves are turning yellow and brown

    • The tomatoes are likely over-ripe. Set the tomatoes on the counter away from the window and they will ripen. Tomatoes that are mushy off the vine are over-ripe.

  2. Hi, One particular tomato plant produced a good set of tomatoes on the lower truss. Then, all was going well with the 2nd truss flowering fine. THen t my dismay the center of the flowers, actually the bottom end of the petals where they join the tiny (looks fertilised fruit) but can’t tell, are turning brown and then the fruit gives up.without reaching a size of more than 1-2 mm. Help/

    • Flowers will die if pollination is incomplete; be sure to give each truss a gentle shake to help pollen drop. Hight temperatures and too much nitrogen in the soil can also cause flowers to abort.

  3. Why are the blooms breaking at the elbow? I have all plants on differing soil, yet all the blooms break. Is this just a watering problem?

    • Blossoms can fail if the weather is too chilly (below 50F) or too hot (greater than 95F); they can also fail due to lack of moisture or too much moisture–keep the soil just moist; blossoms will also fail if they are not pollinating–tomatoes are self-pollinating, give the blossom trusses a gentle shake once flowers open; this will help the pollen fall.

  4. Planted a LARGE garden for the first time this year, we brought in commercial compost/soil mixture and built raised rows. I have probably 50 tomato plants in different rows (all of the same soil). One row of soil has all of the tomatoes growing with deformed stems and curled leaves. The other rows are all fine, any suggestions? I just recently installed drip irrigation and mulched all the rows heavily hoping that will help.

    • If all of the plants in one row or bed are failing there is likely a soil-related problem: too much nitrogen in the soil or soil that has been tainted by a chemical are possibilities. Has that row been fertilized or treated in a manner different from the other rows? Has that row missed watering? There is likely a specific reason–you will have to be a detective for a day or two to figure it out.

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