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Physiological Disorders of Trees: Blossom End Rot

Introduction

Blossom end rot is a common physiological disorder of several important fruits and vegetables. It can often be observed in commercial nurseries and home gardens. Blossom end rot is the result of a low concentration of calcium in a plant. Moisture fluctuations, calcium deficient soil, prolonged drought conditions, and other environmental stressors can induce blossom end rot in vulnerable plants. Blossom end rot often culminates in the basal end of the affected plant becoming necrotic. Crops affected by blossom end rot are often unfit for consumption. Gardens and nurseries plagued by blossom end rot will generally produce a lower crop yield.

Distribution & Habitat

Blossom end rot occurs globally, wherever susceptible plants are present.

Hosts

Blossom end rot affects cucumbers, eggplants, melons, peppers, squash, and tomatoes.

Disorder Cycle & Symptoms of Blossom End Rot

Blossom end rot typically occurs when a damp spring is followed by a dry summer. The sudden shift in moisture availability impacts vulnerable crops as they are becoming established. Symptoms of blossom end rot first appear when the fruit or vegetable is ripening. Small, sunken water-soaked areas will form on the basal end of affected plants, and rapidly enlarge. As the spots enlarge, the plant shrinks and becomes flattened. Eventually, the affected areas rot, and turn black or dark brown. The spots may grow to cover up to half of the plant. Several factors can limit a plant’s ability to absorb a sufficient amount of calcium: a lack of soil moisture, an excess amount of nitrogen in the soil, a soil pH that is too alkaline or acidic, soil that is cold, soil that is high in salt, and root damage suffered due to poor cultivation or mechanical practices.

Management

  • As blossom end rot is a physiological condition, it cannot be treated using fungicides or insecticides.
  • It the damaged portion of the plant is small, it may be trimmed off.
  • Severely necrotic crops should be removed and discarded, or composted. Apply a liquid calcium fertilizer or lime to the soil after removing the affected plants. This will increase the calcium content in the soil.
  • Maintain a soil pH of around 6.5 for vulnerable plants.
  • Ensure that plants are sufficiently watered, especially during extended periods of drought. A lack of moisture will cause plants to wither, and increase the susceptibility of plants to blossom end rot. When conditions are dry, water plants thoroughly once or twice a week, at a depth of at least six inches.
  • Cover soil in a layer of organic mulch to improve the soil quality, retain soil moisture, and reduce the potential for drought stress.
  • Watering cones can be used to encourage water to penetrate deep into the root system.
  • In cold areas, allow the soil to warm before planting crops. Cold soils inhibit nutrient uptake in plants.
  • Plant crops in soils that drain easily.
  • Avoid cultivating or hoeing near the roots of crops.
  • Use fertilizers that are low in nitrogen and high in phosphorous.
  • Do not over-fertilize plants, especially when they are first developing.
  • Stake tomato plants to provide them with support while they grow.
  • Monitor and maintain gardening records to determine if some crops are more susceptible to blossom end rot than others.

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