A serious disorder of tomato, pepper, cucumber and eggplant, blossom end rot is an environmental problem (not fungal) most often caused by uneven watering or by calcium deficiency. (These can be related; uneven watering can interfere with the uptake of calcium.) This common garden “disease” is often brought on by rapid growth from too much fertilizer, high salt levels or drought.
Blossom end rot symptoms occur on both green and ripe fruits and is identified by water-soaked areas that gradually widen and mature into sunken, brown, leathery spots on the bottom end. In many cases, secondary pathogens, which appear as a black, fuzzy-like growth, attack the affected area and cause complete rotting of the fruit. Blossom end rot will not spread from plant to plant.
Since this plant problem is physiological in nature, fungicides will not work as a control measure. We recommend the following:
- Choose resistant vegetable varieties whenever possible.
- Prevent problems by keeping soil evenly moist and by foliar spraying plants with a kelp or calcium solution.
- Adding high levels of calcium — bone meal, oyster shell or gypsum — to the soil at planting time usually prevents this problem from developing.
- A layer of mulch (straw, compost, grass ) will help conserve soil moisture during the hot, dry days of July and August.
- Foliar applications of Liquid Calcium 5% (1-2 Tbsp/ gallon of water) can be used to correct or prevent deficiencies of this essential nutrient. For best results, combine with a natural surfactant to increase adhesion and spray leaves to the point of run-off.
- Mulching plants will help conserve moisture and provide a more uniform water supply.
- Avoid using high nitrogen fertilizers which accelerate vegetative growth and reduce the uptake of calcium by plants.
Note: There has been quite a buzz lately over red mulch film. Not only does this easy-to-use product conserve soil moisture, but it has been extensively tested to show on average a 20% increase in tomato yields.