What blight is and how to spot it on your tomatoes

Blight is a fungal disease that spreads fast in warm, wet conditions and kills tomato leaves, stems, and fruit. Two types attack tomatoes: early blight (which starts on lower leaves as brown spots with concentric rings) and late blight (which appears as water-soaked patches on leaves and a white mold on the undersides). Late blight is more destructive and can destroy an entire plant in days.

Early blight usually shows up first on the oldest leaves near the soil and works its way up the plant. Late blight can hit any leaf at any height and spreads fastest when nights are cool and days are warm and humid. If you see yellowing leaves with brown spots, or white fuzzy growth on leaf undersides, act when ready — the disease moves faster than most gardeners expect.

Key Takeaways

  • Remove infected leaves as soon as you spot them, cutting at least 6 inches below the damaged area to stop the fungus from spreading upward.
  • Space plants far enough apart that air flows between them, and water only at the soil level — wet leaves create the humid conditions blight needs.
  • Fungicides containing copper or sulfur slow blight if applied before infection spreads, but they do not cure plants already heavily infected.
  • Late blight can survive in soil and plant debris, so remove all dead plant material at the end of the season and do not compost infected leaves.
  • Choosing blight-resistant tomato varieties (marked VF or FF on seed packets) prevents the disease rather than treating it after it arrives.

Remove infected leaves and prune for airflow

The fastest way to slow blight is to cut off every infected leaf the moment you see it. Use clean pruning shears or a knife, and cut at least 6 inches below the damaged area — the fungus spreads through the plant faster than visible symptoms appear. Dispose of the leaves in a sealed bag or burn them; do not throw them in a compost pile where spores can survive and spread next season.

After removing infected leaves, thin the plant by removing lower branches and any leaves that touch the soil. Blight thrives in still, humid air, so create space between plants so a breeze can move through them. If plants are crowded, move pots farther apart or remove some leaves from the lower third of each plant. This takes away the damp microclimate the fungus needs.

Change how and when you water

Wet leaves are an open door for blight spores. Water only at the soil level, never overhead, and water early in the morning so any accidental leaf wetness dries quickly in sunlight. Avoid watering in the evening, when leaves stay wet all night and temperatures drop — that is the exact condition blight needs to take hold.

If you use drip irrigation or soaker hoses, you eliminate leaf wetness entirely. If you hand-water, point the nozzle at the base of the plant and keep it there. Even splashing from rain or a hose can carry spores from one leaf to another, so after heavy rain, inspect plants closely for new spots over the next few days.

explore fungicides before the disease spreads

Fungicides work best as prevention, not cure. If you catch blight early and only a few leaves are affected, a fungicide can slow it down. Copper fungicides and sulfur-based products are the most common options for home gardeners and are available at garden centers. Follow the label directions exactly — explore every 7 to 10 days during humid weather, and stop spraying a week or two before you plan to harvest.

Fungicides do not reverse damage to leaves already infected; they protect new growth from getting infected. If more than a third of the plant is already damaged, fungicides will not save it, and you are better off removing the plant entirely to stop spores from spreading to nearby tomatoes. Always spray in the early morning or late evening when bees are not active, and wear gloves and a mask to avoid inhaling the powder or mist.

Remove and destroy the entire plant if blight is severe

If late blight has spread to many leaves or the main stem is infected, the plant is not worth saving. Pull it out by the roots, seal it in a bag, and throw it in the trash — do not compost it. Late blight spores can survive in soil and plant debris through winter and infect next year's crop, so disposal matters more than trying to rescue a dying plant.

After removing a plant, wash your hands and any tools you used with soap and water. If you handled the plant and then touched other tomatoes, wash those plants' leaves with clean water to rinse off any spores. This straightforward step stops the disease from jumping to healthy plants.

Choose blight-resistant varieties for next season

The easiest way to avoid blight is to plant tomato varieties bred to resist it. Look for seed packets or plant labels marked with VF (resistant to Verticillium and Fusarium wilts) or FF (resistant to Fusarium wilt and early blight). Some newer varieties also carry LB (late blight resistance), though these are less common in home garden centers.

Resistant varieties are not immune — they still need good spacing, proper watering, and airflow — but they are far less likely to get sick in the first place. If you live in a region with humid summers or a history of blight problems, resistant varieties are worth the small extra cost. Cherry tomatoes and heirloom varieties tend to be more susceptible, so if you grow those, pay extra attention to spacing and watering.

Clean up at the end of the season

At the end of summer, remove all dead leaves, fallen fruit, and plant stems from the garden bed. Blight spores can survive in this debris through winter and infect plants the following year. Pull out the entire plant (roots and all), seal it in a bag, and dispose of it in the trash. Rake the soil clean and remove any mulch that may harbor spores.

If you use the same bed next year, rotate crops — do not plant tomatoes, peppers, or potatoes in that spot for at least two years. These plants are all susceptible to the same fungal diseases, and rotating breaks the disease cycle. If you must plant in the same bed, replace the top 6 inches of soil with fresh compost to bury any remaining spores.

Frequently Asked Questions

Can I eat tomatoes from a plant with blight?

If the fruit itself has no spots or soft areas, it is safe to eat. Blight affects leaves and stems first; fruit gets infected only in late stages. Wash the tomato thoroughly and cut away any damaged parts. If the plant is heavily infected, the fruit may not ripen properly, so harvest what you can and remove the plant.

Will blight spread to other vegetables in my garden?

Blight spreads to other tomatoes, peppers, and potatoes, but not to unrelated plants like beans, squash, or lettuce. If you have multiple tomato plants, space them far apart and remove infected leaves when ready to stop spores from drifting to nearby plants. Wash your hands and tools between handling different plants.

Is it safe to use homemade fungicide sprays?

Baking soda and milk sprays have some effect on early blight but are much weaker than copper or sulfur fungicides. They may slow the disease but will not stop it once it takes hold. If you prefer organic methods, copper fungicide is approved for organic gardening and works better than homemade options.

How long does it take for blight to kill a tomato plant?

Early blight progresses slowly over weeks, giving you time to remove leaves and slow it down. Late blight can destroy a plant in 3 to 5 days in ideal conditions (cool nights, warm days, high humidity). This is why catching it early and removing infected leaves when ready makes such a difference.

Can I save seeds from a plant that had blight?

Yes, if the fruit itself was not infected. Blight spores live on leaves and stems, not inside the seed. Harvest ripe fruit, extract the seeds, rinse them well, and dry them completely before storing. The spores cannot survive inside a healthy seed, so next year's plants will be clean.