Blossom End Rot
Plant disorder
Description
Blossom end rot is a noninfectious disorder of developing fruit, especially tomatoes and peppers, but also eggplants, squash, and melons. It occurs when the growing end of a fruit does not receive enough calcium to build healthy tissue. Often, the soil contains adequate calcium, but irregular watering prevents roots from taking it up consistently or supplying it to fast-growing fruit. Drought followed by heavy watering, damaged roots, excess fertilizer, and salty soil can increase the risk. Affected tissue dies and forms a dark, sunken patch at the blossom end, opposite the stem. The patch may start small and enlarge as the fruit grows. Secondary microbes can invade it and cause further decay, but they do not cause the original disorder. Blossom end rot is most common on early fruit and may become less frequent when moisture and growth conditions stabilize. It does not spread from fruit to fruit.
Symptoms
- Dark sunken patch at the blossom end of fruit
- Rotting fruit
How to Identify
Look for a water-soaked spot at the blossom end—the end opposite the stem. It turns brown or black and becomes sunken, firm, and leathery. The rest of the plant often looks healthy. The spot may later soften if other organisms invade it. Location is the strongest clue: sunscald usually makes a pale, papery patch on a sun-exposed side, while infectious fruit diseases may produce spots elsewhere, sometimes with rings or visible fungal growth. Check several fruit, including young ones, and review recent watering. Blossom end rot cannot be confirmed by a leaf symptom or by finding insects; it is a fruit disorder.
Prevention
Keep soil moisture even, particularly while fruit is forming. Water deeply when needed rather than alternating prolonged dryness with heavy soaking; adjust the amount to rainfall, soil, and weather. Drip irrigation and a layer of organic mulch help reduce fluctuations. Grow plants in well-drained soil, and avoid damaging roots while cultivating or transplanting. Use fertilizer moderately: excess nitrogen encourages rapid growth, and high fertilizer-salt levels can interfere with calcium uptake. Test the soil before adding calcium or adjusting pH. If a test shows low calcium, follow its recommendation for an appropriate amendment; lime may also raise pH, while gypsum generally does not. Choose a suitable soil pH for the crop. Container plants need particular attention because their potting mix dries quickly.
Treatment
First, make watering more consistent and check that water reaches the root zone without leaving the soil waterlogged. Mulch bare soil and address drainage problems where practical. A damaged patch will not heal, but later fruit may develop normally once conditions improve. Remove badly affected fruit if you wish; this can help the plant direct resources to new fruit. A fruit with a small patch can sometimes be used after the damaged portion is cut away, provided the remaining flesh is sound; discard fruit that is extensively rotten or moldy. Review fertilizer use and avoid adding more nitrogen than the crop needs. If the problem persists, test the soil and add calcium only if the result indicates a shortage. Calcium sprays seldom correct blossom end rot because calcium applied to leaves moves poorly into fruit. Fungicides and insecticides will not treat the underlying disorder.
Plants Affected
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