Apple mosaic disease occurs in all apple-producing areas in my country, especially in Shaanxi, Shandong, Shanxi, Hebei, Henan and other apple-producing areas.
Symptoms
The symptoms of mosaic disease mainly appear on the leaves. Due to different varieties and virus strains, symptoms can be divided into five types: (1) Mottled type: usually starting from the small leaf veins, bright yellow lesions of varying sizes, irregular shapes, and clear edges appear. In the later stages, the lesions often overlap with each other. Heal into large lesions. This type is the most common and appears earliest.
(2) Mosaic type: Large patches of dark green or light green discoloration appear on the diseased leaves, with unclear edges. This type is rare and occurs later.
(3) Striped reticular type: The diseased leaves become chlorotic and yellow along the veins, and spread to the nearby mesophyll tissue. Sometimes only the main veins and sub-veins are yellowed, and the discolored part is wider; sometimes the main veins, branch veins, and small veins are all narrowly yellowed, and the entire leaf shows a yellow net pattern. These symptoms also appear later.
(4) Ring spot type: round, oval or nearly circular bright yellow ring spots or annular markings appear on diseased leaves, and the inside of the ring is still green. These symptoms appear latest.
(5) Border type: The edge of the diseased leaf is yellowed, forming a narrow yellow border on the edge of the leaf. The other parts of the diseased leaf are completely normal. This symptom is only seen in a few cases such as Golden Delicious and Green Banana. Occasionally seen on several species.
Under natural conditions, the above symptom types may be mixed on a tree or a branch. Trees with severe mosaic disease will have leaves discolored, necrotic, twisted, shrunken, and even lead to early defoliation; mosaic lesions are prone to round spot disease; the number of new shoot nodes of diseased plants is reduced; the rate of good fruit is reduced, and diseased fruit Not resistant to storage.