There are 3 diseases that affect tomato plants that are very common. Being aware of these disease, how to prevent them, and how to treat them will ensure that you have a bumper crop of tomatoes. Early Blight is a widespread disease in which the older, more susceptible lower leaves are the common initial site of infection ( Source ). It is caused by two types of fungi. Early blight flourishes when it is humid, rainy, or warm. The best way to prevent early blight is to pla