Integrated Control Methods and Technical Key Points for Spinach Downy Mildew

Spinach (Spinacia oleracea L.), also known as Persian spinach, red-root spinach, parrot spinach, etc., belongs to the genus Spinacia in the subfamily Chenopodioideae of the family Amaranthaceae, and is an annual herbaceous plant. The plant can reach up to 1 m in height, with a conical taproot that is reddish, rarely white, and leaves that are hastate to ovate, bright green, with entire or a few tooth-like lobes. There are many varieties of spinach, which can be divided into two variants, prickly-seeded and smooth-seeded, according to seed morphology. Spinach originated in Iran and is widely cultivated in China, making it one of the most common vegetables.

Growing Environment of Spinach

Temperature

Spinach is a cold-tolerant vegetable; the seeds can germinate at 4°C, with the optimum being 15-20°C, and the suitable temperature for vegetative growth is 15-20°C. Growth is poor above 25°C, and the aboveground parts can withstand low temperatures of minus 6-8°C.

Sunlight

Spinach is a long-day crop. Under high-temperature and long-day conditions, the plants tend to bolt and flower. It has low requirements for light intensity and can be intercropped or relay-intercropped with tall-stemmed crops.

Water

Spinach has a large leaf area and tender tissues, and has relatively high water requirements. With sufficient water, the plants grow vigorously with thick flesh, high yield and good quality. Under high-temperature, long-day and drought conditions, vegetative growth is inhibited, reproductive growth is accelerated, and premature bolting is likely to occur.

Soil

Spinach has strong adaptability to soil, but fertile soil with strong water- and fertilizer-retention capacity is still preferred. Spinach is not acid-tolerant, and the suitable pH is 7.3——8.2. Spinach is a leafy vegetable and requires more nitrogen fertilizer as well as appropriate phosphorus and potassium fertilizer.

Integrated Control of Spinach Downy Mildew

Spinach downy mildew is one of the main diseases of spinach, seriously harming the economic benefits of spinach cultivation. So how should spinach downy mildew be controlled in an integrated way?

What is spinach downy mildew?

The disease is caused by a fungus called spinach downy mildew. It mainly damages the upper surface of the leaves. The lesions are pale yellow, irregular in shape and varying in size, with a diameter of 3-17 mm and indistinct edges. After the lesions expand, they connect with each other into patches, and later turn brown and die. On the underside of the leaves, a grayish-purple mold layer is produced on the lesions. The disease develops gradually from the outer leaves to the inner leaves, and spreads from the lower part of the plant upward. In drought, the diseased leaves turn yellow and withered; under high humidity, they mostly rot; in severe cases, the leaves of the whole plant turn yellow and die.

The integrated control methods for spinach downy mildew are as follows:

1. Strengthen cultivation management: rational close planting, scientific irrigation, and reduce field humidity.

2. Select disease-resistant varieties: pointed-leaf type varieties can be selected; or seeds can be collected from disease-free fields or disease-free plants.

3. Chemical seed dressing: for fungus-carrying seeds, dress the seeds before sowing with 50% thiram wettable powder at a rate of 0.4% of the seed weight.

4. Remove diseased plants: when diseased plants are found in the spinach field in early spring, they should be pulled out promptly, taken out of the field and burned.

5. Chemical control: spray promptly at the early stage of the disease. You can spray 25% metalaxyl wettable powder or 25% metalaxyl wettable powder diluted 600 times with water, or 75% chlorothalonil wettable powder diluted 500 times with water, or 64% oxadixyl-mancozeb wettable powder or metalaxyl-mancozeb diluted 400-500 times with water. The above chemicals should be used in rotation, sprayed once every 5-7 days, for 2-3 consecutive sprays.