Tomato Plant Diagnosis: Identifying and Solving Common Tomato Problems

If you’ve joined the multitude of home gardeners this year, chances are tomatoes are a star in your garden. It’s no surprise, as tomatoes are overwhelmingly popular among gardeners. There’s simply nothing that compares to the burst of flavor from a sun-ripened, homegrown tomato, a world away from the often bland offerings of grocery stores.

However, the journey of growing tomatoes isn’t always smooth. Many gardeners face frustrations, from plants that refuse to bear fruit to tomatoes marred by unsightly blemishes. Perhaps you’ve experienced the disheartening sight of seemingly healthy plants overnight turning into skeletal remains, their branches stripped bare.

Welcome to the common challenges of tomato cultivation. This guide is designed to be your comprehensive resource for Tomato Plant Diagnosis. We’ll walk you through identifying common issues, whether they’re just beginning or fully developed, and provide actionable solutions to rescue your plants and ensure a bountiful harvest of delicious tomatoes.

Diagnosing Your Tomato Plant: A Step-by-Step Approach

Before we delve into specific tomato plant diseases and problems, accurate diagnosis is crucial. Misidentification can lead to ineffective treatments and further stress for your plants. Follow these steps to effectively diagnose your tomato plant issues:

1. Pinpoint the Affected Area: Carefully observe your tomato plant. Is the problem localized to a specific area, or is it widespread? Note whether the issue is primarily affecting the fruit itself, the leaves, the stems, the blossoms, or even the roots (if you can gently check).

2. Observe and Compare: Compare the affected plant to your healthy tomato plants, or to images of healthy tomato plants online. What are the key differences? Is there discoloration, unusual growth patterns, wilting, spots, holes, or any unusual textures like fuzz or mold? Document these differences. For instance, healthy tomato leaves are typically a medium green with a soft, fuzzy texture. Note any deviations from this norm.

3. Inspect for Pests: Carefully examine your plants for insects. Look closely on the undersides of leaves, stems, and around the fruit. Are there any visible bugs? If you are unsure about insect identification, take clear photographs. Your local Cooperative Extension agent is an excellent resource for insect identification and can provide valuable insights.

With these diagnostic steps completed, you’re well-equipped to use the following guide to narrow down the potential problems affecting your tomato plants, whether caused by environmental factors, diseases, or pests. If pests are suspected, you may also want to consult resources specifically focused on common tomato pests.

Alt text: Safer Brand 3-in-1 Garden Spray for Tomato and Vegetable plants. Text on image reads: Safer ® brand tomato & vegetable 3-in-1 garden spray® Control fungal diseases, insects and mites with one simple solution! Shop Now button.

Common Causes of Tomato Plant Problems

Various factors can weaken or harm your tomato plants, ranging from environmental stressors to diseases and fungal infections. While some issues can be resolved with attentive care, severe cases may necessitate plant removal to prevent further spread. Understanding the common triggers is key to proactive tomato plant diagnosis and care:

• Nutrient Deficiency (Lack of Fertilizer): Solution: Conduct a soil test to determine nutrient levels. Amend the soil with appropriate fertilizer based on your tomato plant’s growth stage. Consider using a balanced fertilizer or one specifically formulated for tomatoes, such as Safer® Brand Lawn Restore® Fertilizer.

• Excessive Pruning (Over-pruning): Solution: Use tomato cages or stakes for support and avoid excessive pruning. Tomato foliage provides essential shade for the developing fruit, preventing sunscald.

• Calcium Deficiency: Solution: Soil testing is crucial. Amend the soil with lime and gypsum as recommended based on the soil test results to increase calcium availability.

• Premature Planting (Cold Temperatures): Solution: Plant tomato seedlings only after soil temperatures have reached consistently warm levels suitable for your specific Hardiness Zone.

• Inconsistent Watering (Too Much or Too Little): Solution: Establish a consistent watering schedule to maintain even soil moisture throughout the growing season. Avoid extremes of drought or waterlogging.

• Overhead Watering: Solution: Water tomato plants at the base to minimize leaf wetness, which promotes fungal diseases. If fungal issues arise, apply a fungicide like Safer® Brand Garden Fungicide.

• Poor Air Circulation: Solution: Space tomato plants adequately during planting to ensure good airflow. Prune lower leaves as the plant grows to improve air circulation, but avoid over-pruning (as mentioned earlier). If powdery mildew or other fungal issues appear, fungicide application may be necessary.

Tomato Plant Disease Diagnosis: Common Problems and Solutions

With a foundational understanding of common triggers and the diagnostic steps outlined, we can now explore specific tomato plant problems. This section provides a detailed guide for tomato plant disease diagnosis, outlining symptoms, causes, and actionable solutions for each issue.

Alt text: Blossom End Rot on a ripe tomato, showing a dark, leathery patch at the bottom.

Blossom End Rot

• Symptoms: Tomatoes initially appear healthy, but as they ripen, a dark, sunken, leathery patch develops on the blossom end (bottom) of the fruit. Inside, the fruit often appears dry and mealy.
• Cause: Calcium deficiency. This can be due to insufficient calcium in the soil or soil pH imbalances that hinder calcium absorption. Tomatoes thrive in soil with a pH around 6.5 for optimal calcium uptake. Inconsistent watering can also exacerbate blossom end rot, particularly during hot, dry periods.
• Diagnosis and Solution:
  • Soil Test: Conduct a soil test to assess calcium levels and pH. Your local garden center or Cooperative Extension can assist with soil testing and provide recommendations for soil amendment.
  • Calcium Amendment: Lime and gypsum can increase soil calcium, but apply them according to soil test recommendations. Adding crushed eggshells to your compost can naturally increase calcium levels over time.
  • Foliar Calcium Spray: For mid-season prevention, a foliar spray containing calcium chloride can be effective. Apply early morning or late evening to avoid leaf burn.
  • Consistent Watering: Maintain consistent, regular watering to ensure even moisture and calcium uptake.

Blossom Drop

• Symptoms: Tomato plants produce flowers, but the blossoms fall off before fruit develops.
• Cause: Temperature fluctuations, especially nighttime temperatures outside the optimal range of 55 to 75 degrees Fahrenheit. Other contributing factors include insect damage, water stress (too little or too much), nitrogen imbalances (excess or deficiency), and poor pollination.
• Diagnosis and Solution:
  • Temperature Monitoring: Monitor nighttime temperatures, especially during flowering.
  • Plant Support: Ensure plants are healthy with proper fertilization. Use a balanced fertilizer for tomatoes.
  • Pollinator Attraction: Attract pollinators to your garden by planting pollinator-friendly plants like milkweed and cosmos.
  • Pest Control: Manage insect pests that may be damaging blossoms. Consider using neem oil insecticides for pest control.

Alt text: Fruit cracks on a ripe red tomato, showing concentric circular cracks around the top.

Fruit Cracks

• Symptoms: Cracks appear on ripening tomatoes, often in concentric circles around the top of the fruit. Cracks can provide entry points for insects and attract birds.
• Cause: Rapid changes in soil moisture, particularly after periods of drought followed by heavy rain. The rapid water uptake causes the fruit to swell and crack.
• Diagnosis and Solution:
  • Consistent Watering: Maintain consistent watering throughout the growing season to prevent water stress and rapid water uptake fluctuations.
  • Mulching: Apply mulch around tomato plants to help retain soil moisture and regulate soil temperature.

Alt text: Sunscald damage on a ripening tomato, showing a pale yellow to white, papery patch on the side exposed to the sun.

Sunscald

• Symptoms: Yellowish-white, papery patches develop on the sides of ripening tomatoes exposed to direct sunlight. These patches have a dry, bleached appearance and can affect fruit flavor.
• Cause: Overexposure to intense sunlight, essentially “sunburning” the fruit. This is more common when foliage is sparse due to over-pruning or leaf diseases.
• Diagnosis and Solution:
  • Provide Shade: Ensure adequate foliage cover to shade developing tomatoes. Avoid excessive pruning.
  • Support Systems: Utilize tomato cages or staking systems that provide branch support while naturally shading fruit.

Poor Fruit Set

• Symptoms: Abundant foliage but limited tomato production. Few flowers develop, or existing tomatoes are small and lack flavor.
• Cause: Excessive nitrogen in the soil promotes leafy growth at the expense of flowering and fruiting. Inadequate pollination can also be a factor, especially if plants are too densely planted, hindering wind pollination.
• Diagnosis and Solution:
  • Soil Test: Test soil to check nitrogen levels. Amend soil if nitrogen is excessively high.
  • Spacing: Ensure adequate spacing between plants (at least two feet) for good air circulation and pollination.
  • Manual Pollination: If plants are closely spaced or pollination seems poor, gently shake flowering branches to simulate wind pollination.

Alt text: Catfacing on a tomato, showing a deformed, bumpy, and scarred blossom end.

Catfacing

• Symptoms: Tomatoes are misshapen, with a scarred, bumpy, and deformed blossom end.
• Cause: Pollination during cool evenings, when temperatures are around 50 to 55 degrees Fahrenheit. Cool temperatures can cause developing blossoms to fuse or become distorted.
• Diagnosis and Solution:
  • Delay Planting: If catfacing is a recurring issue, consider planting tomatoes slightly later in the season when warmer temperatures are more consistent.
  • Temperature Management: Use devices like “Walls of Water” or black plastic mulch to raise soil and air temperatures, especially during cool nights, early in the season. Black plastic mulch warms the soil during the day and releases heat at night.

Alt text: Leaf Roll on a mature tomato plant, showing leaves curling upwards and inwards.

Leaf Roll

• Symptoms: Leaves, particularly older lower leaves, curl upwards and inwards, rolling from the edges towards the center. In severe cases, up to 75% of the plant can be affected.
• Cause: Environmental stress factors such as high temperatures, waterlogged soil, and excessive pruning.
• Diagnosis and Solution:
  • Monitor Growing Conditions: Ensure proper drainage to prevent waterlogged soil. Avoid over-pruning.
  • No Treatment Needed: Leaf roll, while visually unappealing, typically does not significantly impact fruit production. Focus on maintaining overall plant health.

Puffiness

• Symptoms: Ripe tomatoes appear normal externally, but when sliced open, they are hollow or have large air pockets with minimal fruit pulp inside. Tomatoes may feel lighter than expected. The tomato shape may be angular or boxy.
• Cause: Nutrient deficiencies, particularly under-fertilization, poor soil nutrition, or inadequate pollination.
• Diagnosis and Solution:
  • Fertilization: Ensure regular fertilization throughout the growing season. Use a balanced fertilizer (e.g., 10-10-10) every two weeks or monthly.
  • Soil Enrichment: Incorporate compost and compost teas into your gardening practices to improve soil fertility and provide consistent nutrient availability.

Alt text: Bacterial Canker on a ripe tomato, showing small yellow spots with dark, bird’s-eye rims.

Bacterial Canker

• Symptoms: Small yellow spots appear on ripening tomatoes, often mistaken for cloudy spot disease. Closer inspection (using a magnifying glass) reveals a distinct dark, bird’s-eye-like rim around each yellow spot, differentiating it from cloudy spot.
• Cause: The bacterium Clavibacter michiganensis, which can be introduced through infected plants or tools and spread through rain splash. Bacteria enter plants through wounds, such as insect damage or pruning cuts.
• Diagnosis and Solution:
  • Plant Removal: Immediately remove and discard infected plants (do not compost).
  • Crop Rotation: Avoid planting tomatoes in the same soil for at least three years to prevent bacterial buildup. Practice regular crop rotation.
  • Sanitation: Disinfect gardening tools to prevent disease spread.

Alt text: Anthracnose on a ripe tomato, showing sunken, dark, bull’s-eye shaped spots on the bottom.

Anthracnose

• Symptoms: Dark, sunken, bull’s-eye shaped spots develop on ripening tomatoes, usually on the blossom end. The spots are mushy, and underlying tissue shows black, rotten areas.
• Cause: The fungus Colletotrichum phomoides, favored by warm, humid conditions. Spread through overhead watering, rain splash from infected soil, and infected plants.
• Diagnosis and Solution:
  • Watering Practices: Switch to drip irrigation or water at the base of plants to keep foliage dry.
  • Timely Harvest: Harvest tomatoes promptly as they ripen, as overripe fruit is more susceptible to anthracnose.

Alt text: Early Blight on tomato leaves, showing brown spots with concentric rings (target-like appearance).

Early Blight

• Symptoms: Brown spots with concentric rings (target-like appearance) appear on tomato leaves, starting with older, lower leaves. Yellowing around the spots occurs, followed by leaf browning and drop. Severe cases can defoliate the plant.
• Cause: The fungus Alternaria solani, which can overwinter in soil. Repeated planting of tomatoes (and related plants) in the same location increases disease risk.
• Diagnosis and Solution:
  • Crop Rotation: Rotate crops annually, avoiding planting tomatoes, eggplants, and peppers in the same location in consecutive years.
  • Fungicide Application: Treat infected plants with a garden fungicide as needed.

Alt text: Septoria Leaf Spot on tomato leaves, showing yellow spots with dark gray centers and black dots within the spots.

Septoria Leaf Spot

• Symptoms: Yellow spots appear on lower leaves after fruit set. Spots develop dark gray centers with darker borders and black dots within the center. Foliage eventually dies and drops.
• Cause: The fungus Septoria lycopersici, which infects tomato foliage.
• Diagnosis and Solution:
  • Avoid Overhead Watering: Water at the base of plants to prevent splashing spores and spreading the fungus.
  • Fungicide Spray: Apply a fungal disease control spray, such as Safer® Brand 3-in-1 Garden Spray, to manage Septoria leaf spot.

Alt text: Fusarium Wilt on a tomato plant, showing wilting and drooping foliage.

Fusarium Wilt

• Symptoms: Sudden wilting of tomato plants, often starting on one side of the plant. Wilting worsens even after watering, and the plant can die within days.
• Cause: The fungus Fusarium oxysporum f.sp. lycopersici, which attacks the plant’s vascular system, blocking water and nutrient transport. The fungus persists in soil.
• Diagnosis and Solution:
  • Crop Rotation: Rotate crops to avoid planting tomatoes in the same area each year.
  • Resistant Varieties: Plant wilt-resistant tomato varieties, especially if fusarium wilt has been a past problem.

Alt text: Verticillium Wilt on tomato leaves, showing yellow blotches and browning veins.

Verticillium Wilt

• Symptoms: Yellow blotches appear on lower leaves. Veins within the blotches turn brown, and leaves eventually brown and drop. The disease progresses upwards, stunting plant growth.
• Cause: The soilborne fungus Verticillium albo-atrum, which infects roots and disrupts water and nutrient flow within the plant.
• Diagnosis and Solution:
  • Crop Rotation: Practice crop rotation, as the fungus can persist in soil for extended periods and even in weeds like ragweed.
  • Resistant Varieties: Choose Verticillium wilt-resistant tomato varieties for planting. Treatment options for infected plants are limited.

Alt text: Viral Disease symptoms on tomatoes, showing black spots and unusual striping.

Viral Diseases

• Symptoms: Viral diseases often manifest on the tomato fruit itself, with symptoms like black spots or unusual striping patterns. Differentiate viral symptoms from natural striping in heirloom varieties.
• Cause: Various viruses spread by stress factors like heat, drought, and poor soil health.
• Diagnosis and Solution:
  • Neem Oil Spray: Spray tomato plants with neem oil to help manage viral issues and vectors.
  • Healthy Growing Conditions: Focus on good soil management and use organic fertilizer for tomatoes to promote plant health and natural disease resistance.

Alt text: Powdery Mildew on tomato leaves, showing white powdery patches.

Powdery Mildew

• Symptoms: White, powdery patches appear on tomato leaves and stems, resembling a dusting of powder. Severe infections can cause leaves to yellow and brown.
• Cause: Fungal disease favored by humid conditions and poor air circulation, more common in greenhouses than outdoor gardens.
• Diagnosis and Solution:
  • Preventative Spray: Use a preventative sulfur-based spray to inhibit powdery mildew development.
  • Improve Airflow: Ensure good air circulation around plants by proper spacing and pruning.
  • Treatment: For existing powdery mildew, refer to resources on powdery mildew prevention and treatment.

Share Your Tomato Plant Diagnosis Challenges

We encourage you to connect with the Safer® Brand Community on Facebook to share photos of your tomato plant problems and gardening questions. Our community experts are ready to assist with tomato plant diagnosis and offer tailored solutions. Also, subscribe to the Safer® Brand E-Newsletter for ongoing gardening tips and helpful articles like this one.