梨銹病是一種影響梨樹的疾病，其癥狀在葉片上表現為初期的橙黃色小點，隨后擴大成病斑。這些病斑上會密生針頭大的橙黃色小粒，這些小粒會分泌淡黃色的粘液，干后變為黑色。病斑背面的組織會隆起，形成淡黃褐色的毛狀物，這些毛狀物 later break open, releasing a large amount of brownish-yellow powder (uredospores). The lesions on the leaves eventually turn black and the leaves wither and fall off. Infected leaf petioles develop raised, orange-yellow紡錘形 lesions. Young fruits are attacked, forming nearly circular lesions that start as yellow and turn brown. On these lesions, yellow fungal structures (uredia) emerge, which are composed of elongated, thread-like structures (uredospores). These structures break open, scattering yellow-brown spores that cause the disease to spread. Fruit growth may be slowed or the fruits may become deformed.The pathogen overwinters as mycelium in infected cypress tissue. In the spring, the fungus produces basidiospores that are released when raindrops wet the cones, causing them to swell and eventually split open to release basidiospores. These spores germinate to produce club-shaped structures that give rise to basidiospores. These spores are carried by the wind to susceptible parts of the pear tree, such as young leaves, shoots, and fruits. infection occurs when the temperature reaches 15°C with the presence of water, with the spores needing several hours to invade the plant. The disease's incubation period is 6-10 days and is influenced by temperature and leaf age. Older leaves are less susceptible to infection, and the disease is most active between leaf emergence and 20 days after emergence. Beyond 25 days, leaves are less prone to infection.The severity of the disease is also related to the presence and proximity of cypress trees, especially those within 1.5-3.5 kilometers of the pear orchards. Meteorological factors, particularly in areas with cypress trees, significantly impact disease spread. The pathogen generally infects only young, tender tissues.To control the disease, several measures can be taken:1. Eliminate the alternate host: Remove Cypress and similar alternate hosts within 5 kilometers of the pear orchard. This is an effective measure to control the disease. When establishing new orchards, consider the presence of alternate hosts and avoid planting pears near them.2. Eradicate overwintering fungi: If alternate hosts cannot be removed, apply fungicides to cypress trees to kill overwintering fungi and reduce the infection source. Apply a fungicide, such as 4-5 Bordeaux mixture, before the pear trees begin to bud to inhibit the germination of basidiospores. Apply fungicides during the leaf expansion period and after flowering to prevent spore infection.3. Increase humidity and drought resistance: From mid-May to late June, if there is a continuous hot and dry climate, irrigate the orchard and spray water on each tree to maintain humidity. Apply a film-forming agent to protect soil and tree nutrients from evaporation and to safeguard against climate and pesticide damage.4. Fruit bagging: Bag fruits between 40-50 days after flowering to prevent infection. This practice not only improves fruit appearance and reduces pesticide residue but also effectively prevents disease occurrence.For chemical control, apply fungicides when the disease is active, between leaf emergence and 25 days after emergence. If basidiospores are observed on cypress trees, treat with a fungicide. If the disease persists, use additional chemicals.These management strategies, when implemented correctly, can effectively control pear rust and minimize its impact on pear tree health.