Tomatoes are one of the most popular vegetables to grow in home gardens. However, tomato plants are susceptible to various diseases and pests that can reduce yield and quality.
This article discusses some of the most common tomato plant diseases and pests that affect tomatoes grown in the home garden and provides tips on identifying, managing, and preventing them.
⬇️ Table of Contents
Common Tomato Fungal Diseases
Several common fungal diseases affect tomato plants. Learning to recognize the symptoms can help gardeners act promptly to treat infections:
Tomato Fungal Diseases Chart: Identify And Treat Common Tomato Ilinesses
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|Early Blight||Dark leaf spots with rings||Remove affected leaves, improve airflow, fungicides||Space plants, mulch, resistant varieties|
|Septoria Leaf Spot||Circular leaf spots||Remove affected leaves, avoid overhead watering, fungicides||Space plants, avoid overhead watering|
|Late Blight||Spots on all plant parts||Eliminate the fungicides||Fungicide sprays, remove weeds|
|Fusarium Wilt||One-sided yellowing & wilting||Yellowing leaves stem rot||Clean soil, rotate crops|
|Southern Blight||Yellowing leaves, stem rot||Yellowing leaves stem rot||Solarize soil, rotate crops|
1. Early Blight
Early blight, caused by the fungus Alternaria solani, is one of the most common tomato diseases. It affects the lower, older leaves first. Look for dark brown spots with concentric rings that give them a target-like appearance.
As the disease progresses, affected leaves turn completely brown and drop. Early blight also causes spots on the stems and fruit. To manage it, space and prune plants to encourage good air circulation.
Mulch to prevent soil splashing on tomato leaves. Remove and destroy infected leaves and stems. Fungicides can help protect healthy plants. Choose tomato varieties bred to resist early blight.
2. Septoria Leaf Spot
Septoria leaf spot manifests as small, circular spots on tomato foliage. Spots have dark brown borders and lighter gray or tan centers. Tiny black dots may be visible in the centers, which are the fungus's fruiting bodies.
Septoria starts on the lower leaves and spreads upward. Infected leaves turn yellow and drop. Avoid overhead watering and give plants ample space. Remove diseased leaves promptly. Apply fungicides at the first sign or as a preventive measure.
3. Late Blight
Late blight is caused by the notorious Phytophthora infestans, which triggered the Irish Potato Famine. On tomatoes, it causes greyish-green or brown greasy spots and blotches on leaves, stems, and fruit.
Distinctive white mold may form on infected tissue in humid conditions. Late blight spreads rapidly and can decimate crops. Remove and destroy all affected plant parts. Disinfect tools after cutting out infections. Apply fungicides containing chlorothalonil or mancozeb weekly as a preventive.
4. Fusarium Wilt
Fusarium wilt is a soil-borne fungus that infects tomato roots and stems. Leaves on one side of the plant are yellow and wilt. Cut open the lower stem to reveal brown streaks inside.
Once plants have fusarium wilt, they cannot be saved; the entire plant must be removed.. Prevent it by planting resistant varieties and rotating crops. Avoid introducing it by using only clean soil and plant debris. Solarize soil to kill fungal spores.
5. Southern Blight
Southern blight causes yellowing and wilting foliage, which results in them collapsing and dying. The fungus forms a white mold at the base of the stem. Remove and destroy affected plants immediately.
Solarize soil and practice crop rotation to reduce fungal populations. Avoid wounding plants when cultivating.
Tomato Bacterial Diseases
Bacterial diseases can also be problematic for home garden tomatoes. Some of the most prevalent bacterial diseases include:
Tomato Bacterial Diseases Chart
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|Bacterial Disease||Pathogen||Symptoms||Transmission||Prevention & Management|
|Bacterial Spot||Xanthomonas species||Small water-soaked spots on leaves/fruit||Contact, water||Prune for airflow, copper spray, remove diseased plants|
|Bacterial Speck||Pseudomonas syringae pv. tomato||Small black spots on leaves/fruit||Contact||Use disease-free seed and transplants, copper spray, remove diseased plants|
|Bacterial Canker||Clavibacter michiganensis||Raised stem/leaf lesions||Tools, wounds||Crop rotation, tool sanitation, copper spray, remove diseased plants|
|Bacterial Wilt||Ralstonia solanacearum||Rapid wilting||Soil, roots||Resistant varieties, pathogen-free transplants, remove diseased plants|
|Pith Necrosis||Pseudomonas cichorii||Stem pith browning||Wounds||Avoid injury, crop rotation, tool sanitation, remove diseased plants|
|Bacterial Soft Rot||Erwinia carotovora||Fruit/stem rot||Wounds||Avoid injury, tool sanitation, reduce wetness, remove rotted plants|
6. Bacterial Spot
Small, water-soaked, raised spots form on leaves and fruits infected with Xanthomonas campestris pv. vesicatoria. Spots become scabby as plants mature. Fruit spots are raised and crusty.
This disease persists between seasons on tomato volunteer plants, weeds, and crop debris. Some strains have developing fruit that are copper resistant.
Purchase certified, disease-free seeds and transplants. Promote airflow. Apply copper sprays preventatively, combined with other fungicides, if copper-resistant strains are present. Eliminate weed/volunteer hosts. Sterilize tools during harvest.
7. Bacterial Speck
Pseudomonas syringae pv. tomato causes bacterial speck, which leads to small black spots on foliage, stems, and fruits. The spots contain a yellow halo. This disease spreads rapidly in warm, wet conditions. Use disease-free seeds and transplants.
Apply copper bactericides preventatively.
8. Bacterial Canker
Clavibacter michiganensis subsp. michiganensis infects through wounds and natural openings, causing raised stem and leaf lesions.
Cankers may exude bacteria. Fruit lesions are sunken and scabby. This bacteria can spread systemically through the plant's vascular system once it enters. Copper sprays are often ineffective for treating systemic infections.
If a bacterial canker is identified, promptly remove and destroy the infected green fruit. Also, avoid planting tomatoes or other solanaceous crops in the same spot for at least one year, as the bacteria can survive in plant debris.
Practice crop rotation and sanitize tools to help protect healthy plants grown. Copper applied preventatively may help protect healthy plants.
9. Bacterial Wilt
Avoid introducing through resistant varieties, crop rotation, and pathogen-free transplants. Once present, it is very difficult to control bacterial wilt.
While not as common, other bacterial threats like pith necrosis, slimy stem rot, and hollow stem can occasionally impact tomato health.
Careful inspection, sanitation practices, protective sprays, and preventative measures are the best ways to protect tomatoes from bacterial invaders.
Viral Diseases of Tomatoes
Tomatoes can be impacted by several viral pathogens that are difficult to control once plants become infected. Preventing introduction is critical. Common viral diseases include:
Viral Tomato Diseases Chart
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|Tobacco Mosaic Virus (TMV)||Distorted leaves with mosaic patterns, stunted growth||Infected seed, plants, tools||Use virus-free seed/transplants, sterilize tools, remove and destroy immediately|
|Tomato Spotted Wilt Virus||Ring spots on fruit, bronze mottling on leaves, stem streaking||Thrips feeding||Virus-free transplants, reflective mulch, control weeds/thrips, remove and destroy promptly|
|Tomato Yellow Leaf Curl Virus||Stunted growth, yellow curled leaves, poor fruit set||Whiteflies||Resistant varieties, UV reflective mulch, control weeds/insecticidal soaps|
|Cucumber Mosaic Virus||Leaf mosaic, mottling, curling, shoestringing||Aphids||Control aphids, remove and destroy infected ones immediately|
|Alfalfa Mosaic Virus||Yellow stippling, shoestringing, dwarfing||Aphids, seed transmission||Control aphids, remove infected plants|
|Tobacco Streak Virus||Necrotic rings on fruit, dried leaf margins||Thrips||Control thrips, weed management, remove the infected|
|Potato Y Virus||Vein clearing, leaf mosaic, necrosis||Aphids, whiteflies||Insect control, remove infected plants|
|Tomato Ring Spot Virus||Fruit deformation, oak leaf patterns on leaves||Nematodes, infected tools||Avoid shared tools, nematode control, and remove infected plants|
10. Alfalfa Mosaic Virus
This virus causes mottled yellow leaves and circular lesions on fruit. It is transmitted by aphids from nearby infected alfalfa fields and can be a major problem for gardens located near commercial alfalfa crops.
There are no chemical controls, though using silver reflective mulch may help repel aphids. The best strategy is to plant resistant tomato varieties.
Avoid locating tomato gardens near commercial alfalfa fields that may harbor the virus. Remove and destroy any infected plants immediately to prevent spread.
11. Tobacco Mosaic Virus
(TMV) is a major viral threat for tomatoes. It causes distinct light and dark green mottling and distorted, shoestring-like leaves.
Fruits develop necrotic lesions and abnormal ripening patterns. TMV is easily spread mechanically through contact with plants, seeds, and gardening tools.
Once a plant is infected, there is no cure. The best management is prevention:
- Purchase hot-water treated, disease-free seeds and transplants
- Monitor closely and remove any immediately
- Sterilize hands, tools, stakes, and surfaces thoroughly after contact with plants
- Control aphids that can spread TMV
- Do not put tobacco products like cigarettes in contact with plants
TMV can persist in soil and infected plant debris for years, so prevention is critical. Any infection must be swiftly eliminated before it spreads throughout the garden or greenhouse. Using resistant varieties like 'Geronimo' also helps protect plants.
12. Tomato Spotted Wilt Virus
This virus causes ring spots on fruits, bronze mottling on leaves, and stem streaking.
It is transmitted by thrips feeding. Use virus-free transplants, control weeds, apply reflective mulch, and monitor for thrips. Remove and dispose of promptly.
13. Tomato Yellow Leaf Curl Virus
Sick plants exhibit stunted growth, yellowed curled leaves, and poor fruit set. Whiteflies spread this virus.
Plant-resistant varieties, use UV reflective mulch and control weeds/infected plants. Insecticidal soaps can help manage whitefly populations.
14. Cucumber Mosaic Virus
Leaf mosaic, mottling, curling, and shoestringing are symptoms of the cucumber mosaic virus. This virus causes severe mottling, leaf curling, yellowing, and shoestringing of foliage. It is transmitted by aphids from infected weeds to tomato plants.
To control, use reflective plastic mulches and insecticidal soaps early in the season to control aphid populations. Remove and promptly destroy any sick plants to prevent spread. Do not compost infected tomato plants.
Vigilance, prompt removal of diseased tomato plants, using virus-free transplants, insect control, and other preventative measures offer the best protection against cucumber mosaic virus and other tomato viral diseases.
Tomato Plant Pests
In addition to diseases, home garden tomatoes can be affected by various insects and animals. Some of the major issues include:
Tomato Pests Chart
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|Hornworms||Missing foliage, caterpillars||Handpick & destroy Bt spray||Monitor plants closely|
|Cutworms||Chewed stems near soil||Collars around stems, beneficial nematodes||Monitor soil at night|
|Fruitworms||Holes in fruit||Row covers, handpick worms, Bt spray||Monitor ripening fruit|
|Whiteflies||Yellowing leaves, flying insects||Sticky traps, insecticidal soap||Monitor the undersides of leaves|
|Flea Beetles||Tiny holes in leaves||Row covers, neem oil/soap||Monitor young plants|
|Aphids||Curled, yellow leaves||Chewed stems near the soil||Knock off ladybugs, insecticidal soap|
Aphids are tiny, soft-bodied insects common in many gardens, including those growing tomatoes. They are typically green or black in color and are often found in clusters on the undersides of leaves or young stems.
These pests feed by piercing the plant tissues and sucking out the sap, which can lead to various problems. Aphid feeding can cause leaves to curl, yellow, and wilt. It can even stunt plant growth and reduce fruit yield in severe cases.
Large green caterpillars that feed on foliage. Hand pick off plants and destroy. Use Bt spray if infestations grow. Target small worms.
17. Stink Bugs
Stink bugs, known for their distinctive odor when disturbed or crushed, are a common pest in many gardens, including those growing tomatoes. They are shield-shaped insects in various colors, from green to brown to gray.
Stink bugs feed by piercing the skin of the tomato fruit and sucking out the juices. This feeding results in dimpled or sunken areas on the fruit, often surrounded by a discolored halo.
Plump caterpillars chew through stems at the soil level. Apply beneficial nematodes or collar seedlings. Hand-pick from beds at night.
19. Tomato Fruitworms
Fruitworms, a common pest in tomato gardens, have a penchant for boring holes into ripening tomatoes. To protect your precious crop, consider the following strategies:
- Deploy row covers at the onset of flowering. This will act as a barrier, preventing adult fruit worms from reaching your plants and laying eggs.
- Regularly inspect your tomato plants and promptly remove any fruits showing signs of infection and any visible worms.
- Apply Bacillus thuringiensis (Bt) sprays. This is a naturally occurring bacterium that acts as a pesticide, effectively controlling the fruitworm population.
Tiny flying insects transmit viruses. Use yellow sticky traps and insecticidal soaps. Avoid virus-infected transplants.
21. Flea Beetles
Tiny hopping beetles chew small holes in leaves. Apply insect barriers early on. Use neem oil or insecticidal soaps.
Slimy mollusks feed on seedlings and ripening fruit. Remove debris and boards that harbor them. Trap using boards or beer.
Careful inspection, hand removal, barriers, traps, and targeted organic treatments can help manage without harming beneficial insects.
Tomato Fruit Rots
Warm, humid conditions promote several fungi that cause rotten, decayed areas on ripening tomato fruits, reducing yields. Major tomato fruit rots include:
Tomato Rot & Fungus Chart
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|Anthracnose||Sunken black lesions||Remove infected fruit, fungicides||Space plants, avoid wetting leaves|
|Buckeye Rot||Circular spot on fruit||Avoid overhead watering, remove infected fruit||Stake plants, space plants|
|Late Blight||Brown greasy lesions||Eliminate infected plants||Fungicide sprays, remove weeds|
|Blossom End Rot||Sunken spot on bottom||Consistent watering, add calcium||Monitor soil moisture|
The fungus Colletotrichum causes sunken, dark lesions on ripe fruit. Pink spore masses form in the center. It also infects stems. Pick fruits promptly when ripe. Remove diseased fruit and use preventative fungicides.
24. Buckeye Rot
Phytophthora fungus leads to small, soft spots with concentric rings. As lesions enlarge, centers turn brown-black. Stake plants and avoid wetting leaves. Improve drainage and airflow.
25. Botrytis Gray Mold
Under cool, humid conditions, Botrytis cinerea grows fluffy gray mold on fruit. Provide ventilation and reduce free moisture. Remove affected fruits and apply protective fungicides.
26. Blossom End Rot
Not a true rot; this disorder causes a sunken black spot on the blossom end. It is caused by calcium deficiency. Maintain even soil moisture and supplement calcium to prevent it.
Preventative Measures Against Tomato Diseases
Preventative practices are critical to avoid the introduction and spread of pathogens in the tomato garden:
- Purchase certified disease-free tomato seeds and transplants to avoid bringing pathogens into the garden
- Practice crop rotation between tomato families each year to disrupt disease cycles
- Monitor for and control insect pest populations that can transmit viruses and bacteria
- Sterilize gardening tools and equipment between plants and rows using a 10% bleach solution or alcohol wipes
- Remove and dispose of any infected tomato plant debris or nearby weeds that can harbor pathogens
Following these proactive measures can greatly reduce the likelihood of diseases establishing and spreading through the tomato garden. An ounce of prevention is truly worth a pound of cure when it comes to tomato health.
Selecting Disease-Resistant Varieties
- There are often multiple races or strains of common tomato pathogens like Fusarium, Verticillium, viruses, etc.
- The prevalence of specific races and strains can vary regionally.
- When selecting tomato varieties, choose ones with resistance to diseases that are common in your local area.
- Check with your county extension office about problematic diseases and recommended resistant varieties for your region.
- When purchasing seeds or transplants, look for disease resistance (denoted by acronyms like VFN, TSWV, etc.) listed in the descriptions.
- Planting varieties with targeted disease resistance gives your tomatoes a head start against common local pathogens.
Consulting local resources and selecting locally-adapted disease-resistant tomato varieties based on regional disease pressures can help prevent major issues in the garden.
Preventing Tomato Physiological Disorders
Several non-pathogenic issues can affect tomato fruit development:
- Monitor soil moisture closely and maintain consistent levels to prevent fluctuations that can trigger cracking or blossom end rot.
- Use drip irrigation or soaker hoses rather than overhead watering.
- Add calcium supplements to the soil or foliar feed plants to prevent calcium-deficiency induced blossom end rot.
- Provide steady air temperatures and protection from cold/heat extremes that can cause catfacing and blossom drop.
- Stake or cage plants early in the season to avoid later root damage that can reduce calcium uptake.
Paying close attention to soil moisture, nutrition, and environmental conditions can help prevent physiological disorders that impact tomato fruit quality and yields.