Identification and Control methods of main Diseases of Radix Isatidis

Radix Isatidis is a cruciferous plant Isatis indigotica, which is used as medicine with dried roots and leaves, and has the effect of clearing away heat and detoxification and cooling blood. There are many diseases in the process of cultivation, and the common diseases are as follows:

I. Radix Isatidis downy mildew

The main results are as follows: 1. The disease occurs first in the leaves near the ground in the lower part of the symptomatic plant, and gradually spreads to the upper leaves. At the initial stage of the disease, only gray-white downy mildew appeared on the back of the leaf, and there was no obvious disease spot on the leaf surface. The injured part was uneven, and further developed into small green spots, then brown spots, severe brown spots, brown spots, the edges of diseased leaves also became brown and withered, until the whole leaf dried up and died.

2. Control measures ① should remove the diseased and residual leaves during harvest and deal with them centrally in order to reduce the source of overwintering disease. ② should pay attention to drainage, ventilation and light transmission, reasonable close planting and reduce humidity. Spraying in the early stage of ③ can control the disease in the early stage so as to avoid spreading. It can be sprayed once with 1 ∶ 1 ∶ 100 × 150 Bordeaux solution or 65% Dysen zinc 500x solution, or 25% Ruidui wettable powder 1000 times solution. Pay attention to spraying the back of leaves when spraying.

2. Grey spot of Radix Isatidis

1. There are small disease spots on the diseased leaves, 2mm in diameter, grayish white in the middle, brown at the edges, thin and easy to perforate. In the later stage of the disease, the disease spot continued to expand to the whole leaf withered and yellow and died. A mildew layer appears on the front of the leaf when it is wet.

2. The control measures are the same as downy mildew.

III. Radix Isatidis root rot

The main results are as follows: 1. When the symptom root is damaged, the fibrous root and the main root tip are damaged first, showing dark brown, until the vascular bundle of the root system shows brown pathological changes. In the later stage, the whole root rotted, the aboveground plants wilted and withered gradually.

2. Control measures ① rotation. ② chooses sandy loam with good drainage to plant. The initial stage of ③ was irrigated with 1000 times carbendazim or methyl topiramate.

IV. Sclerotinia sclerotiorum

The main results are as follows: 1. The symptom root, stem, leaf and pod were damaged by water-immersed bluish brown disease at first, and then the whole leaf rotted, leaving only leaf veins. When the stem was damaged, the cortex rotted, the stem ruptured into hemp, covered with hyphae, and there were black mouse fecal sclerotia inside and outside the stem and leaves, and the sclerotia was the most at the base of the stem near the soil surface. In the later stage, the whole plant withered and yellowed and died.

2. Control measures ① rotation of flood and drought. Sclerotia rot after immersion in water for one month, and rotation of flood and drought can effectively reduce bacteria. ② rainy season pay attention to field drainage, reduce humidity, reasonable close planting, ventilation and light. At the initial stage of the onset of ③, 65% zinc was sprayed.