How to prevent and control downy mildew in spinach? Detailed explanation of prevention and integrated treatment methods
The disease is caused by a fungus called spinach downy mildew. It mainly affects the upper surface of the leaves; the lesions are pale yellow, irregular in shape and varied in size, with a diameter of 3-17 mm and indistinct edges. After the lesions expand, they join together into patches, and in the later stage they turn brown and the leaves die; on the underside of the leaves, a grayish-purple mold layer forms on the lesions. The disease spreads from the outer leaves...
The disease is caused by a fungus called spinach downy mildew. It mainly affects the upper surface of the leaves; the lesions are pale yellow, irregular in shape and varied in size, with a diameter of 3-17 mm and indistinct edges. After the lesions expand, they join together into patches, and in the later stage they turn brown and the leaves die; on the underside of the leaves, a grayish-purple mold layer forms on the lesions. The disease gradually spreads from the outer leaves to the inner leaves, and from the lower part of the plant upward. In dry conditions the diseased leaves turn yellow and wither, while under high humidity they mostly rot; in severe cases the leaves of the whole plant turn yellow and die. The control methods are as follows:
I. Strengthen cultivation management: rational close planting, scientific irrigation, and reducing field humidity.
II. Select disease-resistant varieties: pointed-leaf type varieties may be used; or collect seeds from disease-free land or disease-free plants.
III. Chemical seed dressing: since seeds can carry the fungus, before sowing the seeds may be dressed with 50% thiram wettable powder, at a dosage of 0.4% of the seed weight.
IV. Remove diseased plants: in early spring, if diseased plants are found in the spinach field, they should be removed promptly, taken out of the field and burned.
V. Chemical control: in the early stage of the disease, spray 40% phosethyl-Al wettable powder at 200-250 times dilution, or 58% metalaxyl-mancozeb wettable powder at 500 times dilution, or 72.2% propamocarb aqueous solution at 800 times dilution, once every 7-10 days, for 2-3 consecutive times.