Nothing is more disheartening for a home gardener than walking out to the vegetable patch and seeing those beautifully plump, ripe tomatoes afflicted with nasty rot. After months of tending, watering, weeding, and waiting, it can feel like your hard work has been for nothing as tomato after tomato succumbs to disease and decay. But don’t despair! With a few preventative measures and prompt action, you can get ahead of common tomato troubles and enjoy a bountiful harvest.
What Causes Tomatoes to Rot?
Tomatoes can become afflicted by several common culprits that lead to rotting fruit:
- Blossom End Rot – Caused by a calcium deficiency in the plant, blossom end rot causes a sunken, brown leathery patch to form on the bottom of the tomato. It usually appears before the tomato is fully ripe. This deficiency can occur when the plant is unable to uptake sufficient calcium from the soil due to drought stress, saturated soils, or improper pH. Ensure plants receive consistent weekly watering of 1-2” and test soil pH, aiming for a range of 6.0-7.0. Side dress with calcium supplements like crushed eggshells or bone meal. Mulch helps maintain optimal soil moisture.
- Early Blight – This fungal disease causes dark brown or black spots to appear on the leaves and stems. It eventually spreads to the tomatoes, causing ugly black lesions and rot. Early blight thrives in warm, wet conditions. To discourage it, avoid overhead watering, stake plants for improved air flow, prune foliage to reduce density, and destroy any fallen leaf debris harboring the fungus. Organic fungicides can help protect plants when applied at first sign of spotting.
- Late Blight – Another fungal invader, late blight starts by creating brown spots on the leaves and stems. It quickly spreads to the tomatoes, covering them in fuzzy white fungal growth and causing rapid decay. Late blight can spread alarmingly fast and devastate tomato crops once it takes hold. To prevent, choose late blight resistant varieties, rotate planting sites, remove volunteers from last year’s crop, avoid overhead watering, and destroy any infected plants immediately. Protectant fungicides applied early in the season may help deter infection.
- Fruit Cracks – Large cracks in the tomato skin allow disease organisms and pests access to the inside of the tomato, leading to accelerated decay. Cracking is caused by fluctuation in soil moisture, usually periods of heavy rain following dry spells. Maintaining consistent soil moisture by using drip irrigation and mulch can help prevent cracking. Also avoid applying excessive nitrogen fertilizer which causes plants to outpace fruit development.
- Pest Damage – Insects and animals can damage tomatoes, creating openings for rot to take hold. Common culprits include hornworms, slugs, stink bugs, blossom end rot, aphids, cutworms, mice, squirrels and birds. Monitor plants closely for signs of chewing damage, holes, and frass (insect waste). Hand pick larger pests, use row cover to exclude smaller pests, and apply organic insecticidal solutions for heavy infestations. Deter mice/squirrels with fencing and scare tactics.
- Physiological Disorders – Issues like catfacing (deformities), puffiness, blotching, growth cracks, and cloudy spot can arise from extremes in temperature and moisture during flowering and fruit formation. Provide optimal growing conditions and consistent soil moisture to help avoid. Discard any affected fruit.
- Sunscald – Exposure to intense sun can cause white, blistered patches on tomatoes. Sunscald is most common on green tomatoes or portions of the fruit not shaded by foliage. Ensure tomatoes are adequately shaded as they ripen.
How Can I Prevent My Tomatoes From Rotting?
The best defense is a good offense when it comes to combating tomato troubles. Here are some tips for keeping your tomatoes healthy and rot-free from the start:
- Start with disease-resistant varieties – Look for tomato varieties labeled as resistant or tolerant to common fungal diseases like early and late blight, verticillium wilt, fusarium wilt, tobacco mosaic virus, nematodes and more. Disease resistance gives your tomatoes a fighting chance against infections.
- Stake or cage tomatoes – Keeping tomatoes off the ground prevents slugs and other pests from accessing ripening fruit. It improves air circulation to discourage fungal and bacterial growth. Use tall sturdy stakes at planting and tie plants loosely to provide support as they grow. Or surround plants with tomato cages.
- Water at the roots – Use soaker hoses, drip lines or water gently at the base to deliver water directly to the root zone. This keeps moisture off the leaves, stems, and fruit where it can promote disease development. Avoid overhead watering.
- Mulch around plants – A 3-4 inch layer of shredded leaves, straw, or other organic matter around the base of the plants acts as a barrier to prevent soil from splashing up onto the plants. It also helps retain soil moisture and reduce weed competition.
- Improve soil quality – Prepare planting beds by mixing in several inches of aged compost or other organic material. This provides nutrients for strong growth and improves moisture retention and drainage to avoid extremes that stress plants.
- Practice crop rotation – Don’t plant tomatoes in the same spot as last year, as this allows soil-borne disease organisms and pests to overwinter in the area and rapidly re-infect plants. Rotate plantings to a new area each season.
- Apply calcium regularly – Mix calcified seaweed, eggshells, bone meal or other natural calcium amendments into the soil prior to planting. Side dress established plants monthly with calcium supplements to prevent blossom end rot.
- Prune selectively – Remove suckers and lower leaves to encourage air circulation. But leave enough foliage to shade developing fruit. Over-pruning stresses plants and exposes fruit to potential sunscald.
- Use row covers – Covering plants with fabric row covers excludes insect pests, protects against cold temperature swings, and provides shade. Remove during flowering for pollination.
- Scout regularly for problems – Closely monitor plants for leaf yellowing or spotting, stunted growth, wilting, insect frass, and other issues. Take action immediately at first signs of trouble. Early intervention can prevent major disease and pest damage.
- Test soil nutrients – If plants exhibit nutrient deficiency symptoms, test soil to determine pH and nutrient levels. Adjust pH and amend soil as needed to provide optimal levels for vigorous growth. Proper nutrition helps fortify plants against disease.
- Remove damaged leaves/fruit – Pick off and destroy any leaves or tomatoes afflicted with fungal spotting, rot, catfacing, insect damage or other issues. This keeps disease and pests from spreading. Don’t compost diseased material.
What Do I Do If My Tomatoes Start to Rot?
Even if you follow best practices, you may still encounter an occasional rotting tomato. Here’s what to do:
- Act quickly! – As soon as you spot a rotting tomato, remove and discard it in the trash or a sealed compost bin. Don’t add diseased tomatoes to the compost pile. Time is of the essence when disease appears to prevent spread to healthy fruit.
- Clean up the area – Remove any tomato debris from the soil surface where the rotting fruit fell. These remnants contain disease spores that can reinfect plants. Throw away any partially rotted tomatoes still on the vine.
- Assess adjacent tomatoes – Carefully inspect other ripening tomatoes in the vicinity, as well as the leaves and stems, for early signs of disease or pest damage. Remove any questionable tomatoes or plant parts. This helps halt disease progression.
- Treat fungal infections – If fungal lesions are present on leaves or remaining fruit, treat promptly with an organic fungicide like copper spray, neem oil or Serenade according to label directions. Repeat applications may be needed to protect developing fruit.
- Address insect pests – If hornworms, stink bugs, tomato fruit worms or other pests are responsible, hand pick off larger pests. Apply insecticidal soap, neem oil, Bt caterpillar spray or appropriate organic pesticide for heavy infestations.
- Improve growing conditions – Ensure plants receive 1-2 inches of water weekly, increase sunlight if foliage is overly dense, and side dress with calcium and general fertilizer. Healthy vigorously growing plants can better withstand and outgrow minor pest or disease damage.
- Harvest frequently – Pick tomatoes as soon as they start to show color before diseases have a chance to take hold. Handle gently to avoid bruising. Store picked tomatoes at 45-55°F to slow deterioration.
- Control weeds – Pull emerging weeds which compete for water and nutrients. Weeds can also harbor pests and diseases. Mulch after weeding to block new growth.
- Consider new plantings – If disease and insects persist despite treatment, pull severely affected plants to prevent spread. Start fresh, clean plants in a new location on your property as needed to continue the season’s harvest.
- Clean up thoroughly at season’s end – Remove all tomato vines and stakes from the garden. Dispose of heavily diseased plants in sealed bags with household trash, not the compost pile. Till under remaining plant debris to speed decomposition.
How Can I Tell if My Tomatoes are Still Safe to Eat?
It’s disheartening to watch a tomato slowly rot on the vine. But there is still hope you can rescue tomatoes in the early stages of decline. Here are some signs a tomato can still be safely eaten:
- Firm to the touch – Gently squeeze the tomato. If it still feels firm with just a little give, it is likely fine for eating. Discard tomatoes that are mushy or sunken. Caution is needed, however, if fungal lesions are present on firm fruit, which may have deeper decay.
- Intact skin – Minor skin blemishes, tiny cracks or scarring on the surface are okay if the flesh beneath is still firm. But major cracks or large soft spots often allow decay to penetrate inside – discard these tomatoes.
- No fungal growth – White fungal mycelium growing on the tomato exterior is a sign of advanced decay. These tomatoes should be removed from the plant and tossed. Even a few spots of fungus warrants caution.
- Green shoulders – An overall green shoulder and firm flesh indicate the tomato is underripe. Letting it vine ripen for a few more days improves quality and full color development helps protect against rot issues.
- No unpleasant odor – Bring the tomato to your nose. Mushy, rotten tomatoes give off an unpleasant, fermented scent caused by microorganisms breaking down plant tissues. Ripe, healthy tomatoes smell appealing.
- Interior color – Cut the tomato open. If the inside still appears robust red or pink with nicely formed seed cavities, it should be fine for eating. Discard tomatoes with brown, mushy interiors. Watch for small dark pockets of mold or bacterial growth.
- Inspect the scar – Check the spot where the tomato previously attached to the vine. If decayed and sunken, the scar offers dangerous access for pathogens even if the rest of the tomato looks healthy.
- No leaking juice – When gently compressed, a fresh tomato shouldn’t leak excess liquid. Oozing juice indicates ruptured cells and decay advancing internally. Discard leaky tomatoes.
When a tomato shows early signs of trouble, move swiftly to prevent the spread of disease to healthy fruit. And don’t let a few rotten tomatoes completely spoil your gardening experience. Follow these tips and you’ll be rewarded with a bountiful harvest!