Control of diseases and insect pests of Radix Isatidis

Disease

White rust: caused by a flagellum in fungi. Leaves, stems and flowers can all occur, and there are more on the back of the leaves. Usually too much nitrogen fertilizer, tender plants, more Rain Water, high humidity, sometimes cold and warm, the disease is more serious. There are many sources of continuous cropping disease, and the disease is more serious.

Control methods: (1) and time seedlings, clear ditches and drainage, ploughing and weeding, reduce field humidity, promote seedling growth and enhance disease resistance. (2) the seedlings should be combined with the seedlings, the diseased seedlings should be removed, and the diseased leaves should be removed in the later stage to avoid the spread of germs. In the early stage of ⑶, Bordeaux solution was sprayed to restrain the spread of the disease. ⑷ collected and burned the diseased and residual branches during harvest to eliminate the source of overwintering disease.

Black spot: (1) symptoms. Produce round or nearly round disease spot on the leaf, brown to dark brown, the disease spot often has wheel pattern, there is a green halo around, the disease spot is larger, generally diameter 3-l0mm disease spot has dark brown mildew on the front, namely pathogen conidia. In the later stage, the diseased leaves withered and fell off. (2) the regularity of the disease. The pathogen overwintered with conidia in the diseased part, which was the primary infection source in the following year. It started in May and lasted until October. Among them, the occurrence from June to September is the most serious. The high temperature and rainy season is beneficial to the disease.

Control measures: ① reasonable rotation, clean the countryside, eliminate the source of overwintering bacteria. ② should strengthen field management, increase the application of phosphorus and potassium fertilizer, and improve disease resistance. At the initial stage of the onset of ③, spray 1 100 Bordeaux solution or 65% Dysen zinc 600 × 800 times, once every 10 to 15 days, 75kg per mu for 3 consecutive times.

Gray spot disease: (1) symptoms. The damaged leaves produce small round disease spots, which are slightly sunken. The edge of the lesion is brown and the center is grayish white. The disease spot becomes thin and brittle, easy to crack or perforate. The diameter of the disease spot is 2-mm, and there is brown mildew on the leaf surface, that is, the fruiting body of the pathogen. The disease occurs first from the old leaves and spreads from the bottom up. In the later stage, the disease spots can heal each other, and the diseased leaves turn yellow and die. (2) the regularity of the disease. The pathogen overwintered with the diseased and residual tissue and became the primary source of infection in the following year. Seeds can also carry bacteria to start the disease in early June, and the peak period is from late June to early September. When the average temperature is 23 ℃ ~ 25 ℃, it is beneficial to the disease and spreads rapidly.

Prevention and control measures. ① rotation and cleaning the countryside to reduce the source of bacteria. ② opened ditches and drained water in rainy season to reduce field humidity. At the initial stage of the onset of ③, the protection of Bordeaux solution was sprayed with 1 Vera and 100% Bordeaux solution, or the prevention and treatment was sprayed with 65% Dysen zinc 600 Mel 800 times solution.

Sclerotinia sclerotiorum is one of the main diseases of Radix Isatidis. When the disease is serious, a large number of plants die. (1) symptoms. The roots, stems, leaves and pods were harmed, and the stem suffered the most. In the early stage of the disease, the basal leaves were the first to develop. The disease spot was watery at first, then bluish brown, and finally the leaves rotted, leaving only veins. When it is rainy and humid, the damaged stem is covered with white hyphae, the cortex is soft rot, and the stem is broken into hemp. The stem is hollow with black mouse fecal sclerotia. Sclerotia can be seen on the surface of stem or on leaves. After the damage to the stems and leaves, the branches and leaves wilted and gradually withered. (2) the regularity of the disease. The pathogen overwintered as sclerotia in the soil or mixed among seeds and became the primary source of infection in the following year. During the growth period, the ascospores were scattered by wind and rain, and the spores were infected again to expand the damage. The disease occurs in mid-April, and the peak period is from late April to May. Partial application of nitrogen fertilizer, poor drainage, extensive management and stagnant water after rain are all beneficial to the disease.

Control measures: ① rotation of flood and drought to avoid rotation with cruciferous crops. ② strengthened field management, drained ditches in time after rain, applied less nitrogen fertilizer, increased phosphorus and potassium fertilizer, and improved plant disease resistance. At the initial stage of the onset of ③, 65% Daimen zinc 400 murine 600 times solution was sprayed with 75-lOOkg per mu, once every 7 days, and 3 times successively.

Downy mildew: caused by a flagellum in fungi. It mainly harms the leaves. The disease usually begins in early June and is serious in mid-July. The diseased and residual tissue in the soil is the primary infection area of downy mildew. During the growth of Radix Isatidis, the conidia on the back of diseased leaves were spread by wind and rain and infected repeatedly.

Control methods: ⑴ selected seeds: disease-free plots were selected as seed fields, planting plants were harvested respectively, and seed roots were stored separately. ⑵ cleaning countryside: when digging Radix Isatidis, remove the withered branches and leaves on the ground and reduce the source of the disease. ⑶ pay attention to drainage: high soil moisture is a favorable condition for the occurrence of Isatis downy mildew. Drainage should be done in time after rain to reduce field humidity. Reasonable rotation of ⑷: rotation should be carried out with gramineous crops such as corn. ⑸ spray prevention and treatment: at the initial stage of the disease, use 50% methyl topiramate 800-1000 times, or 5% carbendazim 1000 times.

Powdery mildew: caused by an ascomycete in fungi. The main damage to leaves. In general, the disease is easy to occur because of low temperature and humidity, excessive application of nitrogen fertilizer, dense plants, poor ventilation and light transmission. When drying at high temperature, the disease stops spreading.

Control method: ⑴ removes the stagnant water in the field and restrains the occurrence of disease. Reasonable close planting of ⑵ and reasonable combination of nitrogen, phosphorus and potassium fertilizer can make the plant grow healthily and enhance the disease resistance. The diseased leaves were removed at the initial stage of the onset of ⑶. After harvest, the diseased plants and fallen leaves were removed and burned. ⑷ chemical control: spray 65% Fumet zinc wettable powder 300500 times.

Insect pest

Small bridge-building insects: harm from August to September. The 1st-3rd instar larvae bite the mesophyll, residual epidermis, form transparent dots, and the 5th-6th instar bite the whole leaf. The mature larvae make thin cocoons and pupate at the edge of the leaves or between the stems and leaves. Overwintering as pupa in field weeds in winter, hatching harm in the coming year.

Control method: spray with 1500 times liquid of trichlorfon, focus on the middle and lower old leaves, and the effect is obvious.

Aphids: when aphids occur, they are concentrated on young leaves and shoots to absorb juice, causing leaves and shoots to curl and wither, resulting in poor growth.

Control methods: after harvest of ⑴ Radix Isatidis, remove residual branches and leaves and weeds on the ground, concentrate on burning, and eliminate overwintering insects. ⑵ chemical control: spray with 4% dimethoate 1500 times liquid. Or sprayed with soil pesticides. Soil pesticide preparation method: tobacco gluten 0.5 kg, lime 0.5 kg, water 25 kg into tobacco gluten lime liquid.

Pieris rapae: Pieris rapae, Pieris repe L. The larvae harmed the leaves. Before the 2nd instar, the larvae only fed on the mesophyll, and after the 3rd instar, the leaves formed pores, and green granular feces could be seen.