Many fungal diseases threaten to steal tomato fruits throughout the growing season. But black mold, also known as Alternaria fruit rot, is a late-season disease that targets ripe tomato fruits. It's very closely related to the leaf-spotting tomato disease known as early blight, which occasionally affects early tomatoes with similar fruit-rotting results.
Like many common diseases that affect edibles, black mold requires free water on the plant in order for fungi to germinate and infect the fruit. In times of extended wet conditions — from heavy dews, high humidity, or fall rains that arrive early — the disease can devastate a crop of ripe, harvest-ready tomatoes.
Black Mold Identification/Symptoms: When black mold strikes, tomato fruits develop symptoms that look very similar to the sunken black lesions known as blossom end rot. But instead of appearing on the bottom, blossom end of tomato fruits, black mold appears on the stem end instead.
Lesions may look shallow and superficial or sink deep into the inner fruit. Unlike the gray mold of botrytis or the white mold of tomato late blight, the progressive mold turns dark black in warm, humid conditions. Rot can occur before and after harvest.
How to Control Black Mold: The conditions that set off black mold typically take late-season gardens by surprise. Once the disease is in motion, there's little time to save your harvest. Prevention is a critical step in protecting against this late-season fruit rot.
Start treatments early in the season, as soon as conditions favor disease development, and apply every 7 to 10 days to maintain control. Treat tomatoes with these products right up to the day of harvest:
- Daconil® Fungicide Ready-to-Use is ideal for treating small gardens, container plants, or individual plants woven into edible landscapes. Just shake and the grab-and-go spray bottle is ready to go. Spray all plant surfaces until thoroughly wet, with particular attention to tomato fruits.
- Daconi® Fungicide Concentrate, designed for use with a hand-held, hose-end, or tank-style sprayer, offers an economical option for larger areas. The convenient measuring cap simplifies measuring concentrate into your sprayer. Add water, mix well, and spray plants to the point of runoff.
Black Mold Tip: Don't let your harvest linger on the vine. Instead, harvest tomatoes as soon as they're ripe. The longer the ripe fruits stay in the garden, the greater the chance that black mold will strike
Always read product labels thoroughly and follow instructions, including guidelines for treatable plants, application rates and frequencies, and pre-harvest intervals (PHI) for edible crops.
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