Anthracnose on tomatoes

Anthracnose on tomatoes is a fruit disease, not a foliage disease. That distinction matters for management: the pathogen lives in soil and on plant debris, splashes onto fruit, and causes the lesions gardeners see when tomatoes begin to ripen and soften. Green tomatoes typically show no symptoms;.

—- title: "Anthracnose on tomatoes" slug: anthracnose-on-tomatoes hub: problems category: "Disease-by-host" description: "Anthracnose appears on ripe tomatoes as sunken, water-soaked circular spots. Identify it correctly, control fruit contact with soil, and apply fungicides at the right timing." date: 2026-06-10 updated: 2026-06-10 author: "Thomas A." reading_time: 8 —-

Anthracnose on tomatoes is a fruit disease, not a foliage disease. That distinction matters for management: the pathogen lives in soil and on plant debris, splashes onto fruit, and causes the lesions gardeners see when tomatoes begin to ripen and soften. Green tomatoes typically show no symptoms; the same fruit develops circular, sunken spots days after it starts to color. By harvest time, a wet summer can turn a large portion of the crop to mush.

I don't grow tomatoes at my Long Island property, so this guide is sourced from University Extension research.

The pathogen

Tomato anthracnose is caused primarily by Colletotrichum coccodes, with some contribution from C. dematium. Per Penn State Extension, the pathogen overwinters in infected plant debris and in soil, where it can persist for multiple years. Spores are splash-dispersed from soil and lower plant surfaces onto developing fruit.

Identification

Fruit symptoms

Per Cornell Cooperative Extension, anthracnose produces:

• Circular, water-soaked spots on the fruit surface, typically 0.25–0.5 inch in diameter at first detection
• Sunken, depressed centers as lesions mature
• Concentric ring pattern within the lesion — rings of color from tan to dark brown
• Tiny black dots in the lesion center — these are acervuli (spore-producing structures), which appear as a pepper-like speckling under magnification
• Secondary rot — the lesion provides an entry point for bacterial and fungal rots, causing rapid soft collapse

Fruit infection begins weeks before visible symptoms, typically when fruit is green, and becomes apparent as fruit softens and ripens. Per Clemson HGIC, warm, wet conditions in August and September — exactly the period of heaviest fruit set on many varieties — create peak disease pressure.

What anthracnose is not

Blossom end rot produces large, leathery black or brown patches at the blossom end and is caused by calcium deficiency, not a pathogen. Early blight on fruit produces dark, concentric lesions with a yellow halo, typically at the stem end. Bacterial speck and spot produce smaller, irregular lesions. Anthracnose lesions are round, uniformly sized, and sunken at the center with the small black dots.

Disease cycle

Per Penn State Extension, the disease cycle is:

1. The pathogen survives in soil and infected crop debris from the previous season
2. Rain or irrigation splashes spores from soil onto developing fruit and lower foliage
3. Spores infect green fruit — infection is invisible at this stage
4. As fruit ripens and cell walls soften, the pathogen colonizes the fruit tissue
5. Lesions become visible on ripe or nearly ripe fruit
6. Infected fruit on the ground or left on the vine produces secondary spore loads that infect neighboring fruit

High temperatures (75–85°F, or 24–29°C) and wet conditions accelerate the cycle. Per Cornell Cooperative Extension, the disease is particularly severe in seasons with wet Augusts and September rains.

Management

Mulching

Per Penn State Extension, applying 2–3 inches of organic mulch (straw, shredded wood, or plastic film) under plants reduces soil splash significantly. This is the simplest and most consistent management step. Apply mulch before disease pressure begins, at transplanting.

Plant spacing and staking

Per Cornell Cooperative Extension, staking, caging, or trellising tomatoes lifts fruit off the ground and improves air circulation, both reducing infection risk. Dense plantings with foliage resting on or near the soil greatly increase anthracnose risk.

Timely harvest

Per Clemson HGIC, harvest fruit promptly as it begins to color. Fruit that is left to fully ripen on the vine has more time to develop symptoms from earlier infections. Harvest at the "breaker" stage (first color change from green) is acceptable for most varieties — tomatoes ripen normally off the vine in warm conditions.

Fungicides

Per Penn State Extension, fungicide applications can reduce anthracnose severity when timed correctly. Begin applications when fruit first sets (not after symptoms appear), repeating on a 7–14 day schedule through the harvest period. Registered active ingredients include:

• Chlorothalonil — effective, broad-spectrum; apply on a preventive schedule
• Copper-based fungicides — OMRI-listed options for organic production; apply every 7 days during wet periods
• Mancozeb — effective but pre-harvest intervals must be observed per label

Per Clemson HGIC, fungicides are ineffective after fruit symptoms appear — lesions do not heal.

Crop rotation

Per Cornell Cooperative Extension, rotate tomatoes and other solanaceous crops out of infested beds for 2–3 years. Remove and dispose of all plant debris at the end of the season. The pathogen overwinters in infected crop residue, so thorough cleanup reduces the following year's inoculum load.

Avoid overhead irrigation

Per Penn State Extension, drip irrigation or soaker hoses reduce leaf and fruit wetness compared to overhead irrigation. If overhead watering is unavoidable, water in the morning so foliage dries quickly.

Common problems table

Frequently Asked Questions

Can I eat tomatoes with anthracnose spots?

The affected portion of the fruit is decayed and should be cut away generously. Per Penn State Extension, the rest of the fruit is usable if the decay has not spread to the interior. However, fruit with large lesions or secondary rot should be discarded.

Does anthracnose infect tomato foliage?

Per Cornell Cooperative Extension, Colletotrichum coccodes primarily infects fruit. It can produce minor lesions on leaves under high-pressure conditions, but foliage disease is not the primary concern. Significant foliage spots on tomatoes are more likely early blight (Alternaria solani), late blight (Phytophthora infestans), or Septoria leaf spot.

If I treated with fungicide this year but still got anthracnose, what went wrong?

Per Penn State Extension, the most common failures are starting too late (after fruit set instead of at first set), applying at intervals greater than 14 days during wet periods, or not achieving adequate fruit coverage with the spray. Fungicides must coat the fruit surface before infection to be effective.

Does composting infected tomato plants spread anthracnose?

Per Clemson HGIC, home compost piles rarely reach temperatures high enough to kill Colletotrichum spores reliably. Dispose of heavily infected plant material in the trash rather than the compost bin.

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Sources

1. Penn State Extension — Anthracnose Fruit Rot of Tomato
2. Cornell Cooperative Extension — Tomato Disease Identification
3. Clemson HGIC — Tomato Diseases and Other Problems