What are the control methods for onion purple blotch?
How do you control onion purple blotch? What damage does onion purple blotch cause? We ask knowledgeable readers to help explain. Purple blotch mainly damages onions and Welsh onions, and also infects and damages garlic and chives. Therefore, Zhongdiwang has compiled the damage and control methods of onion purple blotch, listed in detail below for readers' reference. Onion...
How do you control onion purple blotch? What damage does onion purple blotch cause? We ask knowledgeable readers to help explain.Purple blotch mainly damages onions and Welsh onions, and also infects and damages garlic and chives. Therefore, Zhongdiwang has compiled the damage and control methods of onion purple blotch, listed in detail below for readers' reference.
Damage caused by onion purple blotch:
On onions, purple blotch mainly damages the leaves, flower stalks and bulbs. The lesions first appear starting from the leaf tip, or form at wounds caused by thrips. At first the lesions are small, gray to light brown, slightly purple in the center, with dark gray mold-like growth. The lesions quickly expand into oval or spindle shapes, sunken, dark purple, forming concentric rings, surrounded by a yellow halo.
When humidity is high, the purple blotch lesions expand to cover the whole leaf, often causing the onion leaves to turn yellow, die or break from the bottom upward, seriously affecting the yield and quality of fresh onions.
Purple blotch is prone to occur under warm and humid conditions, and plants are susceptible during the bulb enlargement stage. Fields with sandy soil, dry land, early seedlings, old seedlings, fertilizer deficiency, weak onion growth, or severe thrips damage have more serious disease.
Control methods for onion purple blotch:
Method 1: Clean the onion plantation and remove sources of infection such as diseased plant residues.
Method 2: Strengthen management, apply more base fertilizer and topdressing, so that the onions grow vigorously and their disease resistance is enhanced. After the disease occurs, control irrigation to reduce soil moisture, and control thrips early to avoid causing wounds.
Method 3: Before sowing, soak the onion seeds in a 300-fold dilution of 40% formaldehyde for 3 hours, and wash them thoroughly immediately after soaking.
Method 4: In the early stage of the disease on onions, spray 75% chlorothalonil wettable powder at 600-fold dilution, or 64% oxadixyl-mancozeb wettable powder at 500-fold dilution, 70% mancozeb at 500-fold dilution, 40% daifudan at 500-fold dilution, or 50% iprodione at 1500-fold dilution, copper-ammonia mixture at 500-fold dilution, 2% polyoxin at 30ppm, 50% procymidone 30-50 grams, onion-garlic disease net, and other agents. Any one of the above agents may be chosen, and the various agents should be used alternately, once every 7-10 days, for 3-4 consecutive treatments. Adding 5-10 grams of neutral laundry powder to every 10kg of spray solution can increase the adhesion of the solution.
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