Q: I am growing several kinds of tomatoes and spraying them with Daconil to prevent blossom end rot. Even so, my large tomatoes look perfect on top but the entire bottom is black.
A: Blossom end rot isn’t caused by a fungus. The Daconil spray will have no effect preventing it. The condition is caused by lack of calcium in the blossom end of the fruit when it is very small. Calcium does not move readily in a tomato plant. The best way to prevent the condition is to keep the soil uniformly moist without periods of dry/wet/dry/wet as it grows and sets fruit. There is some evidence that calcium chloride (Stop-Rot, etc) can assist in getting calcium to young fruit if the entire plant is thoroughly sprayed. However, keep in mind that water management when the fruit is small is key.