Gray spot disease mainly damages the leaves and also harms the fruit. It is the main disease of alfalfa. The initial lesions of leaves were pale yellow dots, and they rapidly expanded afterwards, forming irregular large lesions with obvious black bands on the edges. The victim suffers a round, purple-brown lesion that soon craters, and many scattered small black spots grow on the late lesions.
Oxygen Flow control regulators and conserving devices are pressure reducing devices designed to regulate or lower oxygen pressure from a cylinder to levels that can be safely used by the patient. A Regulator simply regulates the (free) flow from an oxygen cylinder. A Conserving Device is an entirely different kind of device that delivers a "pulse" of oxygen as the patient inhales (on demand).
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Prevention methods: 1 Strengthen management, increase tree vigor, and increase disease resistance; 2 Cut off dense branches, increase light transmission, and timely clear the garden to reduce the source of disease; 3 Chemical control: Spray 50% thiophanate 500 to 600 times fluid, or 65 % dexamethasone 500 ~ 600 times, or 50% benzene to l500 times control. From fruit picking to flowering, it can be treated with 0.3% to 0.4% Bordeaux mixture. 
Prevention and treatment of gray spot disease
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