The control method of bitter gourd downy mildew
First, the harm symptoms Bitter gourd mildew mainly damages the leaves. The primary foliar was pale yellow and then expanded. The lesion was limited to a polygonal or irregular shape by the veins. The color gradually changed from yellow to tan to brown. In severe cases, lesions merged into plaques. When the humidity is high, a white moldy material grows on the back of the leaf, sometimes the white mycelium is seen on the leaf surface, and the mildew layer is rarely seen when the weather is dry. The field symptoms resemble the powdery mildew of bitter gourd. Bitter gourd powdery mildew is also harmful to the petiole and stem. At the beginning, more white moldy spots appeared on the tender stems, and then expanded into mildew spots. In severe cases, chlorotic yellow spots appeared. In the fall, a lot of small black spots grow on the stain, namely the ascostic shell of the pathogen. Second, control methods (1) Select disease resistant varieties. (2) Applying compost from retort, clearing trenches, and reducing the humidity in the field can reduce the damage. (3) From the perspective of avoiding diseases, the humidity in the shed is preferably maintained at 90% to 95%, and in particular, the time for dew condensation on the leaves must be shortened or controlled in an intermittent state. Management seeks to reduce the duration of foliar condensation. (4) 70% ethidium phosphine sprayed at the beginning of the disease; Mn-Zn wettable powder 500 times, or 72% DuPont Kelu wettable powder 800 times; when the disease is severe, 700 times fluid can be sprayed, or 69% can be used instead. Manganese zinc wettable powder or water dispersible granules 1000 times or 47% Garnett's wettable powder 800 to 1000 times liquid, bitter gourd is sensitive to copper sensitive seedlings, growth period should be strictly controlled dosage and concentration to prevent A phytotoxicity occurred. Bitter gourd mixed with powdery mildew can be sprayed 69% Anke manganese zinc wettable powder 1600 times plus 20% Triadimefon EC 2000 times, every 10 days or so, continuous control of 2 or 3 times. The drug was stopped 4 days before the harvest. KOKEN Co., Ltd , https://www.hnb-maker.com