What to Do When Water Spinach Gets White Rust? Symptom Identification and Control Methods

Water spinach, originally named Yongcai, also known as Tengtengcai, Wengcai, Wengcai, Tongxincai, Wuxincai, Wengcai, Kongtongcai, Zhuyecai, bears white trumpet-shaped flowers and its stem is hollow in the center, hence the name “water spinach”. It is widely cultivated as a vegetable in rural areas of southern China.

Botanical characteristics of water spinach

Water spinach is a trailing plant with a shallow root system; it has fibrous roots and strong regeneration capacity. The stem is trailing, round and hollow, soft, green or light purple, with a stem diameter of 1-2 cm. The stem has nodes; besides axillary buds, each node can also produce adventitious roots. The internode length is 3.5-5 cm, with the longest reaching 7 cm. The cotyledons are opposite and horseshoe-shaped. The true leaves are alternate, with a smooth surface, entire margins, and very pointed tips; the veins are reticulate, with the midrib distinctly raised. The leaves are lanceolate, long-ovate, or heart-shaped. The leaf width is 8-10 cm, with the widest reaching 14 cm; the leaf length is 13-17 cm, with the longest reaching 22 cm. The petiole is relatively long, about 12-15 cm, with the longest being 17 cm. It is hollow and concave. The fruit is a capsule, nearly round; the seeds are dark brown, with a 1000-grain weight of 32-37 g. Water spinach is propagated by seeds or tender stems; in the north, it is propagated by seeds.

Because after the beginning of summer there is high temperature and frequent rain, water spinach is prone to a disease called white rust, which seriously affects the production efficiency of water spinach. So what are the symptoms of water spinach white rust and how can it be controlled?

What is white rust?

White rust mainly damages the leaves. In the early stage of the disease, slightly raised white nearly round to irregular blister spots, i.e. sporangial pustules, appear on the back of the leaves. Their surface is slightly glossy; on a single leaf there may be as many as dozens of blister spots. When mature, the epidermis of the blister spots ruptures and releases white powdery material, namely the pathogen's sporangia.

Symptoms of water spinach white rust: the lesions occur on the back of the leaves. On the upper surface of the leaves, pale yellow to yellow spots first appear, then gradually turn brown. The lesions expand, and white raised blister spots form on the back of the leaves, nearly round or oval to irregular, sometimes coalescing into larger blister spots. Later, the blister spots rupture and release white sporangia. When the leaves are severely damaged, the lesions are dense, the diseased leaves are deformed, and the leaves fall off.

The control methods for water spinach white rust include the following three points:

First, carry out a 2- to 3-year crop rotation with other vegetable varieties.

Second, before sowing, dress the seeds for sterilization at a ratio of 300 g of 35% metalaxyl per 100 kg of seeds; third, in the early stage of the disease, spray with 50% copper metalaxyl wettable powder at 6000-7000 times dilution, or with 72.2% propamocarb aqueous solution at 8000 times dilution, once every 7-10 days. Reinfection. Rainwater and insects can also spread it; whether seeds can transmit it remains to be studied. Cool and humid nights, warm days, heavy fog and dew, and sticky wet soil conditions are favorable for the occurrence and epidemic of this disease.

III. Control methods

1) Select disease-free seeds and treat seeds: select a disease-free plot for seed production; soak newly purchased seeds in 50 degrees C warm water for 25 minutes, cool, and then sow.

2) Strengthen garden management: choose a plot with high terrain, good drainage, and ventilation for planting. Apply sufficient fertilizer and increase phosphorus and potassium fertilizer. Irrigate reasonably and do not let the onion field become too wet. When diseased plants are found, pull them out and bury them promptly. After harvest, thoroughly remove diseased residues, treat them centrally, and carry out deep plowing to reduce sources of inoculum.

3) Chemical control: spray in the early stage of the disease, once every 7-10 days, for 3-4 consecutive sprays. Commonly used agents include 1:1:240-300 Bordeaux mixture, 40% fosetyl-aluminum wettable powder at 200-300 times dilution, 25% metalaxyl wettable powder at 500-1000 times dilution, 75% chlorothalonil wettable powder at 500-600 times dilution, 65% zineb wettable powder at 500-700 times dilution, 64% oxadixyl, M8 wettable powder at 500 times dilution, and 66.5% propamocarb aqueous solution at 700-1000 times dilution.