TOMATO BLOSSOM END ROT
The problem presents itself like this. When a tomato is about 1/3 to 1/2 of its' full size, round water soaked areas on the blossom (bottom) end of the fruit appear. Over time the spots become sunken, turn brown to black, and become leathery.
Blossom end rot is not caused by a disease organism. It will not spread from plant to plant or fruit to fruit. It's a physiological disorder that is a result of an inadequate supply of water and calcium available to the rapidly developing tomato fruit.
This can be caused by any of the following:
1. Excessive or heavy rains that smother root hairs. Tomatoes should be planted in well drained soil.
2. Cultivating too close to the plant, thus damaging the roots. When cultivating, stay at least one foot away from the base of the plant and try not to go down more than one inch.
3. Extreme fluctuations in soil moisture, especially from very wet to very dry (drought). Maintain uniform soil moisture to allow for a steady growth rate. Use mulch if necessary.
4. Do not over fertilize. Avoid high nitrogen fertilizers as they effect calcium uptake.
When the problem arises, supplemental calcium should be supplied. Grind up egg shells and spread them around the base of the plant. Apply lime which is a good source of calcium. Bonide has a ready to use product called Rot Stop which is a calcium chloride spray. It can simply be sprayed on the plant to give it a quick shot of calcium.
Again, blossom end rot is not a disease. Tomatoes that have it are still edible. Just cut away the damaged area.