|What is blossom end rot on tomatoes|
Blossom end rot is perhaps the most common physiological disorder you will experience with growing tomatoes. Typically it shows itself as a circular, dark brown patch of skin found at the flowering end of the fruit – hence the name. As the fruit grows this unsightly dark patch gradually toughens and shrinks back into the fruit.
What Causes Blossom End Rot?
Because of this, the problem of calcium deficiency is most noticeable in areas where there is significant cell division, and when you consider the rapid growth generated in the production of a tomato fruit it is understandable why cell death (necrosis) can occur in this region when the availability of calcium is restricted.
Calcium deficiency should not be confused with lack of availability as its uptake can be inhibited by high levels of potassium, magnesium and /or ammonium-nitrogen within the root environment. Surprisingly other factors that can inhibit the uptake of calcium can include water stress and high humidity. To a lesser extent boron deficiency can also be a factor as it is needed for the transport of calcium within the plant's tissues.
How to Treat Blossom End Rot
It's probably worth doing a pH test first as acidic soils have naturally lower levels of calcium compared to alkaline soils. If this is the case then apply lime to the soil, but go by the manufacturer’s recommendations according to soil type - try to end up with a soil pH of about 6.5. You can also consider spraying the affected fruit with solutions of calcium nitrate or calcium chloride. This is applied at a concentration of 2 grams per litre on a fortnightly basis.
In the greenhouse environment it's important to keep humidity levels low, so make sure there is good ventilation throughout the growing space. Air circulation can be further improved by removing the older, lower leaves from the base of the plants.
Never apply fertilizer to dry soil and any irrigation that is in place must be sufficient to maintain a good, steady, growth rate for the plants – this is particularly important during the summer period. For outdoor tomatoes, giving the soil a good mulch can be very helpful in maintaining water levels in the soil especially in times of moisture stress. When feeding your plants use either a specific tomato fertilizer or use fertilizers that are low in nitrogen, but high in superphosphate.
Although all of these solutions will help in some way to reduce the incidence of Blossom End Rot in tomato plants it is always best to try and avoid the conditions that promote it in the first place. By using good plant husbandry as outlined above you will hopefully never have a incidence to worry about controlling.
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RHS: BLOSSOM END ROT
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