Onion purple spot

Onion purple spot disease is the most important disease of green onions. In addition to harming onions, it also harms onions, garlic, and leeks.

Symptoms mainly affect the leaves and pedicels, and can even harm the bulbs. At the early stage of the disease, the lesions were small, slightly concave, and later gradually enlarged, oval or spindle-shaped, brown to purple. When wet, black mold layer was formed on the lesions, and there were concentric ring patterns, and the diseased part was easily broken. Onions and onions on the lesions purple brown, garlic, yellow brown spots, humidity, dark brown moldy material, arranged in a roulette, severe disease leaves and peduncles withered. After cutting the bulbs and necks, they became semi-wetly corroded and the tissues became red or yellow and gradually dark brown or black. The storage period can continue to be developed.
Pathogen? Alternaria porri (Ell) Ciferri is a semi-known phylum Subgenus, known as Alternaria sp. Conidiophores solitary or 5 to 10 bunches. Less branches, upper ones conidia. Conidia long rod-shaped, spore length. Its optimum growth temperature 24 ~ 27 °C.
?? The characteristics of the disease? Mycelium in the body of the mycelium, seedlings or overwintering with the disease in the soil, you can also continue to damage the stored onion. When condi- tions are appropriate, conidia are produced and spread by air currents and rain. From the host's wounds, stomata or epidermis infestation to Bo? Warm, moist and conducive to hair growth? Excessive management, poor drainage, continuous rain, excessive density, declining growth and other serious diseases.
?? Prevention methods
? 1, rotation and non-onion crops for more than 2 years of rotation.
2. Chemical control: 70% Antecan wettable powder 600 times liquid, 43% Halonic suspension 3000-4000 times liquid, 70% mancozeb 500 times liquid, 75% chlorothalonil 600 times liquid, 64% antiviral 500 times, 58% methionine 500 times spray, 70% mancozeb WP 500 times, 64% antitoxic WP 500 times.


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