How to effectively prevent and control downy mildew in edamame
Introduction to edamame downy mildew:
[Symptom characteristics] Mainly damages leaves. Irregular small spots ranging from yellowish-white to yellow appear on the leaf surface, and corresponding gray loose mold signs (sporangiophores and sporangia) appear on the underside of the leaves. In severe cases, the leaves dry up and fall off.
[Pathogen and disease characteristics] The pathogen is Peronospora manshurica (Naum.) Syd. ex Gaum., belonging to the Mastigomycotina. The fungus overwinters as oospores on diseased residues or seeds. When conditions are suitable the following year, the oospores germinate and produce sporangia, and the sporangia release zoospores, which spread by rain splash and invade from the embryonic stem, forming systemic infection. After disease onset, new sporangia form on diseased leaves, germinate and release zoospores, and spread further by wind and rain. During the growing season, repeated secondary infections occur, allowing the disease to spread. The disease tends to become epidemic when the temperature is 20-24°C with rainy and highly humid weather. Differences in disease resistance among varieties are unclear. Among nearly 50 edamame varieties promoted in China in recent years, some varieties that generally show relatively strong disease resistance, such as Luqingdou No. 1 (i.e. 87-5, Shandong), Wuyueba and Liuyueba (Zhejiang local varieties), Edou No. 4 and No. 5 (Hubei), Wuxiang edamame (August and September podding edamame, Zhejiang), Yanchuanqing edamame (introduced from Japan), Zhoudou 30 (western Hubei) and others, whether they are also resistant to downy mildew still requires further observation in various regions.
Control methods for edamame downy mildew:
(1) Select disease-resistant, high-yield good varieties according to local conditions.
(2) Disinfect seeds before sowing (dress seeds with 35% metalaxyl at 0.3% of seed weight, or 72% Curzate wettable powder, or 69% Anke mancozeb wettable powder).
(3) Plant at a reasonable density, manage fertilizer and water well, improve air movement between plants, and enhance plant resistance.
(4) Spray pesticides in time to prevent and control the disease. When the plants are close to closing the rows, and at the latest when disease is first seen, spray 25% metalaxyl wettable powder at 600-700 times dilution, or 40% fosetyl-aluminum at 200 times dilution, or 72% Curzate wettable powder at 600-800 times dilution, or 69% Anke mancozeb wettable powder at 600-800 times dilution, or 64% Sandofan wettable powder at 600 times dilution, 1-2 times or more, alternating sprays, spraying evenly and thoroughly.