Catface on tomato

This common problem on some types of tomatoes is caused by cultural problems – not insect or disease. In catfacing, the blossom end of the fruit becomes severely deformed.  It is most common on larger, flat-bottomed cultivars.

The exact cause of catface is not known, but is suspected to be related to improper pollination, excessively cold or high temperatures during the development of fruit, alternating dry and wet soil conditions during fruit development or other stresses during fruit development.

The fruit itself is still edible, just unsightly. To prevent catfacing, ensure you mulch well, keep your plants well protected from temperature extremes, avoid pesticide use, and ensure that you maintain a diversity of flowering plants within your yard to encourage pollinators.