So what is the cause of this nasty destroying fungus? It is something so simple that most people don't realize they are causing it. The cause is watering your tomato plants too late in the day and they are remaining wet during the night. That prolonged wetness is a perfect environment for the powdery mildew to proliferate. To prevent powdery mildew, do not water your plants in the afternoon, water in the morning so that the plants have a chance to dry out.
Another thing to keep in mind is the fact that your tomato plants should not be overly bushy with leaves. You need to remove excess leaves and branches to allow air and light to circulate around and through your tomato plants and the tomatoes. Proper staking of your plants also helps.
