Jerry Brust, IPM Vegetable Specialist, University of Maryland; jbrust@umd.edu
This is just a quick reminder that we are in very dry conditions right now and tomato plants are putting on large fruit at the same time they are flowering profusely. Everyone knows that blossom end rot is caused by too little calcium in the fruit while it is developing, usually from the time of flowering until it is the size of a quarter. Most of the blossom end rot I have seen in tomato is due to too little water supplied to tomatoes during dry, very hot periods like we are having now. Some varieties are much more sensitive to dry conditions and will show severe blossom end rot symptoms while other varieties do not. Your tomato plants are going to need more water than you may be used to giving them over the next few weeks if conditions remain hot and dry.
Blossom end rot on tomato fruit