 Not like a fungus problem that's treatable with a fungicide. This rot develops at the base of the flower where it was attached to a young tomato. In its early stages, it's unnoticeable unless you look really close to the tomato for a soft depression or a soft water-soaked spot. So again, these are not things you are going to see early. You're going to notice them as soon as the tomato starts to ripen.