Septoria leaf spot and early blight are common foliar diseases of tomatoes in home gardens. Fungal diseases overwinter on plant debris in the soil. Fungal spores are splashed onto plant foliage by raindrops or splashing water and invade the plant tissue when leaf surfaces are wet. Rainy weather in spring and early summer favors development of foliar diseases on tomatoes.
Little can be done to control foliar diseases on tomatoes in the current growing season. However, good cultural practices can help prevent foliar diseases from reoccurring in future years. This fall, carefully remove as much of the tomato debris from the garden as possible and destroy it.