Blossom End Rot
















Blossom End Rot is a physiological disorder that is caused by a calcium imbalance within the plant.  It affects tomatoes where the tissue of the blossom end of the fruit (the area of the tomato that is opposite the stem of the plant, also known as the basil end) and as it breaks down, it turns dark brown to black and rots, thereby reducing the  overall productivity of the plant.  Many gardeners who have grown tomatoes in their garden are quite familiar with this problem.  Heavy losses may take place if preventive measures are not taken to rectify the problem. Blossom end rot can also be found in peppers, cucumbers, melons, and squash, however it's most commonly found in tomatoes.

Symptoms of blossom end rot may occur at any stage of development.  The disorder starts as a small, water-soaked spot which then enlarges and darkens rapidly as the tomato develops. The spot may enlarge until it covers as much as one-half of the entire tomato surface, or the spot may remain small and superficial. Large lesions soon dry out and become a flattened, black, and leathery in appearance and texture. Blossom end rot can occur in green as well as red tomatoes.

Calcium is required for the tomato to grow and calcium acts like a glue as it binds the cells together.  Tomatoes absorb calcium through our watering of plant; typically however, calcium is not fast to relocate.  Calcium deficiency will not spread from plant to plant or from tomato to tomato since this disorder is physiological in nature and the use of fungicides and insecticides are of no value as a means of control.

This disorder is dependent upon a number of environmental conditions, especially those that affect the supply of water and calcium in the development of tomatoes. The movement of calcium within the plant is dependent of active transpiration.  Certain things that may influence the uptake of water and calcium by the plant may have an effect on the severity of blossom end rot.  Generally speaking, calcium moves from the roots of the plant and into the leaves were it remains.  It does not move from the leaves and then into the tomato with the exception of Hi-Yield ‘Calcium Nitrate’ which is the only form of Ca that moves into the fruit.  We recommend using this form of calcium at the time of planting and again when little tomatoes start to form and finally two or three weeks later.

Calcium deficiency is especially prevalent when rapidly growing, succulent plants are exposed suddenly to a period of drought. When the roots fail to obtain sufficient water and calcium to rapidly developing tomatoes, the tomato may become rotted on their basal ends. Another common problem is cultivating too close to the plant as this may this harm the root system which effects the uptake of water and other minerals. Tomatoes planted in cold, heavy clay soils may develop a poor root system. Since they are unable to supply adequate amounts of water and nutrients to plants during times of stress, blossom end rot could result. Soils that contain excessive amounts of soluble salts may also predispose tomatoes to this disorder. The availability of calcium to plants decreases rapidly as total salts in the soil increase.

To sum this up, inconsistent watering practices, root damage, cold temperature or cold soil conditions, excessive heat, too much nitrogen, and/or too much salt in the soil are all situations that can lead to blossom end rot.

control  measures...

Control of blossom end rot is dependent upon maintaining adequate supplies of moisture and calcium to the developing tomatoes. Tomatoes should not be excessively hardened or too succulent when planted. Tomatoes should be planted in well drained, adequately aerated soils. Tomatoes planted early in cold soils are more likely to develop blossom end rot on the first set of fruits, with the severity of the disease often subsiding as the weather warms.  Planting tomatoes in warmer soils will help alleviate part of the problem. Irrigation must be sufficient to maintain a steady even growth rate to plants.

Mulching of the soil is helpful in maintaining adequate supplies of soil water in times of moisture stress. When cultivation is necessary, it should not be too close to plants or so deep that the feeder roots are injured. Shading plants can be helpful when hot, dry winds occur.  The use of fertilizer that is low in nitrogen, but high in phosphate are excellent fertilizers and Ferti-lome ‘Tomato and Vegetable Food’ will help alleviate problems related to blossom end rot. Another factor that will help with blossom end rot is Ferti-lome ‘Yield Booster’.  The foliage can be sprayed to help control this disorder; however foliar treatment is not a substitute for proper treatment of the soil.

other thoughts…

Many avid gardeners are aware that differences exist among different varieties of tomatoes in regards to the susceptibility to blossom end rot.  Once a tomato has blossom end rot, the problem cannot be reversed in that tomato.  Tomato’s that are infected with this disorder should be removed so the energy can be redirected to healthy tomatoes.  Tomatoes infected with blossom end rot can be eaten as long as no other problems are present, however we recommend discarding any tomatoes infected with blossom end rot.

Tomatoes perform best when the pH of the soil is between 5.8 and 6.5.  Tomatoes need about one to three inches of water each week and they perform best when they are watered deep several times each week rather than a light, but often watering schedule.  Many gardeners have found that indeterminate and semi-determinate tomatoes are less prone to this disorder since it’s somewhat easier to regulate calcium intake.

To improve fruit set, we recommend using Ferti-lome ‘Tomato & Pepper Set’.  Apply to the back of the blossom and to the adjacent stems.   Repeat this process every 10 to 14 days.  This product will not only increase the yield of the plant, but will also increase the ripening process.

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