Leaf Symptoms. Lesions appear within five to seven days under warm, moist conditions between 82ºF and 86ºF. The early leaf symptoms appear as slightly raised, tiny, blister-like lesions (Fig. 3). When leaf lesions are young, the yellow halo is most prominent (Fig. 4). As the lesions age, they turn tan to brown, and a water-soaked margin appears surrounded by a yellow ring or halo. The center of the lesion becomes raised and corky. The lesions are usually visible on both sides of the leaf (Fig. 5).