Garlic leaf blight mainly damages leaves, leaf sheaths, stems and other parts, with the disease mainly affecting leaves. After the leaves are infected, they show 4 types of disease, namely tip die type, streak type, purple spot type and white spot type. When the disease is severe, the lesions on the leaves can extend through the leaf nodes to the leaf sheaths, causing the leaf sheaths to wither and turn yellow. When the field is humid, a brown to black mold layer will appear on the surface of the diseased spots. The lower leaves of the pointed withered type initially show white round spots. After gradually expanding, the leaf tips become dark brown and necrotic, with faint purple-brown diagonal stripes on both sides. Striped spots mainly occur in the middle and lower leaves. When the leaves are infected, brown streaks appear throughout the entire leaf, developing along the midrib or on one side of the leaf. The purple spot type can be seen throughout the growth period and is the main spot type in the field. The leaves are affected, and the lesions are oval or irregular in shape. The center is darker purple-brown, the edges are light brown, and there are withered yellow necrotic lines at both ends. After spreading, the leaves will become withered and yellow. During the bolting stage, dense round and oval small white lesions appear on the upper leaves with obvious edges. Some white spots later develop into purple spots.

Garlic blight mainly damages the leaves. In the early stage of infection, pale to light yellow water-soaked spots appear in the middle or the tip of the leaves, with light green edges. The lesions expand quickly, with half of the leaf or 3-5 days. The entire leaves will wilt and the spots will rot when the humidity is high, and a sparse gray-white layer of rain will appear on them. The diseased flower stems will also become water-soaked and rot, causing the whole plant to die.