Powdery Mildew Tomato
"Leaves on infected tomato plants develop irregular, bright yellow blotches; severely affected leaves die but seldom drop. Spots of dead tissue, sometimes surrounded by a yellow halo, eventually appear in the blotches. There are no lesions on stems or fruit. Rarely, a gray mycelium develops on the lower leaf surface of infected leaves. Severe infections kill leaves and result in sunburn fruit and weakened plants."