How to Prevent and Treat Black Root Disease in Lotus Root? A Full Breakdown of Practical Methods

Lotus root is native to India and was introduced to China very early; by the Southern and Northern Dynasties period, lotus root cultivation was already quite widespread. Lotus root is slightly sweet and crisp, can be eaten raw or cooked, and has considerable medicinal value. Its roots, leaves, flowers, stamens, and fruits are all treasures and can all be used as nourishing medicine. Made into powder, lotus root can aid digestion and stop diarrhea, stimulate the appetite and clear heat, nourish and strengthen the constitution, and help prevent internal bleeding. It is an excellent liquid food and nourishing delicacy for women, children, the elderly, and those who are frail and sickly, and during the reign of Emperor Xianfeng of the Qing Dynasty it was designated as a tribute item for the imperial kitchen.

Lotus root is suited to growing in hot, rainy seasons. South of the Yangtze River it is mostly planted in early to mid-March to April, while in the Beijing area it is mostly planted in early May. For the lotus field, choose clay soil that is deep, rich in organic matter, and slightly acidic to nearly neutral. For the seed lotus root, select a mother lotus root or a fully mature daughter lotus root that has the traits of the variety, plump lotus head, intact terminal bud, thick and large lotus body, small lotus nodes, thick and sturdy rear section, and bright color. The planting method should ideally involve digging, selecting, and planting in sequence, or the roots can be pre-sprouted before planting.

The lotus field generally keeps 5-6 cm of shallow water in the early stage to promote sprouting and leaf growth, with a water depth of 15-16 cm in the middle stage; in the later stage the water is shallowed again to favor lotus root formation. During growth, oxygen in the air combines with iron in the soil to form reddish-brown rust spots of ferric oxide, which adhere to the surface of the lotus root. When the lotus leaves wither, the respiration of the lotus root slows, and the rust spots gradually decrease due to reduction. Therefore, picking the leaves before harvest makes the rust spots easier to wash off. The leaf navel, leaf stalk, and underground stem are connected by air-conducting tissue, so the leaf stalk must not be broken, lest water enter and cause the plant to rot.

Black root disease of lotus root is an important physiological disease of lotus root, occurring in all growing regions. After it generally occurs, losses reach 20%-30%, and in severely affected plots losses reach about 80%. So how should black root disease of lotus root be prevented and treated?

Symptoms of black root disease of lotus root:

This disease mainly affects the stem nodes. After it occurs, the stem nodes turn brown to dark brown, and later rot and deteriorate, becoming inedible. The leaves emerging upward first show chlorosis between the veins, then turn brown or purplish brown, spreading inward from the leaf margins, and eventually the whole leaf dies.

Causes of black root disease of lotus root:

Black root is mainly caused by applying green manure too much and too late, high temperatures, and the application of undecomposed organic fertilizer, which causes physiological disorders in lotus root. Usually, when rice fields are converted to lotus root cultivation, the disease is severe under high temperatures in summer and autumn.

Prevention and treatment methods for black root disease of lotus root:

1. In winter, keep deep water soaking the field and apply fully decomposed organic fertilizer.

2. Manage water scientifically. Per hectare, green manure application should preferably be 37500 kg, and no later than the stage when the fourth standing leaf has unfolded. After black root disease is found, cultivating the field and letting it dry can reduce the incidence of the disease.