Anthracnose (Tomatoes) Description: Appears on ripe fruit, producing small, round, sunken spots. These spots grow larger, and soon the whole fruit is affected and develops a water rot. Solution: Use Soap-Shield® Fungicidal Soap or Copper Dust starting after setting out plants, then every 7-10 days. Apply more frequently if disease is increasing rapidly. Reapply after rain. Weed Barrier Mats also help by keeping fungi in the soil from splashing on leaves during rains.