Downy mildew, viral disease, soft rot, and dry heart disease are the main diseases of cabbage.
1. The downy mildew's performance can occur from the seedling stage to the heart-filling stage. It mainly damages the cabbage leaves. It begins with the lower leaves and begins to develop watery, light yellow polygonal lesions on the leaves, and gradually expands. It turns yellow-brown, and when it is severe, the leaves are dry and inedible. The severity of the disease is closely related to climate, species, and cultivation techniques. In autumn, rainfall is high, relative humidity is higher than 70%, which is favorable for downy mildew; sowing is too early, density is too high, partial nitrogen fertilizer is applied, and poor field drainage occurs.
Prevention:
(1) Agricultural control: Firstly, it is suitable for close planting, with medium and early-maturing varieties planting 2500-3000 plants per acre, and late-maturing varieties planting 2000-2400 plants per acre. The second is balanced fertilization followed by multiple-element compound fertilizer to avoid partial nitrogen fertilizer application; Third, timely drainage after the rain to prevent and control the accumulation of water in the fields.
(2) Chemical control, available at the beginning of the disease can be 40% BFA 800 times solution, 58% metalaxyl MnZn 500 times solution or 1.5% LHW 1000 times foliar spray; Ke Lu 800 times liquid foliar spray, once a week, even spray 2 3 times.
2. Viral diseases: Symptoms can be divided into two types. One is mosaic type: the leaves produce uneven green patches or mosaics; the second is shrinkage type: the heart leaves appear to be deformed, hard and brittle.
The occurrence of this disease is related to climate, management and other factors. After sowing cabbage, it encounters high temperature and drought, root growth is inhibited, and disease resistance is reduced. In addition, high temperature and drought are favorable for the occurrence of aphids, high risk of virus transmission, and serious viral disease. In addition, extensive management, lack of water, lack of weight loss.
Prevention and control measures: cabbage virus disease spread by the locusts, so the control of aphids is critical, can be used 10% imidacloprid 2000 times spray, once every 7-10 days, and even prevent 2-3 times. After the cabbage is infected, spray 1.5% of Shilingling No. 2 800 times liquid or virus killer, Kangrun No. 1 1000 times liquid foliar spray once a week for 2-3 times.
3, soft rot disease: from the cabbage rosette period to bald heart occurs, often two types, one is wilt type: Chinese cabbage wilting at noon on sunny days, sooner or later recover, the whole plant continued to die after a few days; two is soft rot Type: Damaged cabbage leaf petiole or leaf ball is sticky and soft rot, and emits odor.
The severity of the disease is related to climate, gargle, sowing date, etc. If there is more rainfall, surface water accumulation is conducive to the disease, and sowing is too early and the plots are seriously affected.
Prevention and control measures: (1) Agricultural control: Avoid continuous cropping, prevent the water in the ground area, remove the diseased plants in time, bring out the destruction in the field, and prevent the spread. (2) Chemical control: 72% of agricultural streptomycin 3000 times, 3% of Kecong 1000 times, and 20% of Runge 500 times can be sprayed alternately, once a week, and sprayed 2-3 times.
4, dry heart disease: generally occurs in the rosette stage of Chinese cabbage, young leaves show dry edge, symptoms to the ball stage, the upper part of the leaves gradually dry, yellow, leafy paper was dry paper, veins yellow to dark brown, The site of attack is mainly in the middle of the leaf ball.
The disease is a physiological disease, mainly caused by the lack of calcium and manganese nutrients.
Prevention:
(1) Add organic fertilizer.
(2) Chemical control: Spray with 0.7% manganese sulfate plus green Fenwei 3 before the cabbage seedling stage, rosette stage or balsamic stage.
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