Bitter gourd powdery mildew occurs in bitter gourd plants. Different varieties have different resistance to powdery mildew, mainly on leaves, followed by petioles and vines. The disease is caused by fungal monofilaments and is an obligate parasite. Parasitic life on the living body, the symptoms are mainly harmful to the leaves. Usually in warm and humid weather, excessive application of nitrogen fertilizer or insufficient fertilizer, plant growth is too strong or adversely affected. Mainly harmful to the leaves.
Primary near-round pollen, in severe cases, the powder spots are densely covered on the leaf surface and can fuse, causing the leaves to turn yellow, eventually causing dryness, causing plant growth and blocking of the melon, shortening the growth period and reducing the yield.
Harmful symptoms
First, small round powdery mildew spots grow on the front or back of the lower leaves of the plants, gradually expanding and thick, and soon become a piece. In the later stage of the disease, the whole leaf was covered with white powder, which turned grayish white, and finally the whole leaf turned into a yellow-brown dry. Most of the disease begins from the middle and lower leaves, and then gradually spreads to the upper leaves.
Incidence condition
The pathogen can survive on the flowers such as melons and vegetables in the greenhouse and overwinter, and the conidia are produced after wintering and spread by airflow. The pathogens sprout from spores to invade for more than 20 hours, so the disease develops rapidly and tends to be a pandemic in the short term. The bacteria can be active at 10 to 30 °C, and the optimum temperature is 20 to 25 °C. Relative humidity of 45 to 75% is rapid, and when it is less than 25%, conidial germination can cause morbidity, and more than 95% of the disease is significantly inhibited.
Control method
1. The prevention and control of bitter gourd powdery mildew is first carried out in rotation, not in combination with cucurbitaceae vegetables. Before planting, the ground new high-fat film is used to prevent soil layer, which isolates the source of pests and increases the emergence rate.
2. Before sowing, bitter gourd soak the seeds with warm water of about 55 °C, continue to soak for 12 hours after natural cooling, seed dressing with new high-fat film before sowing, repel the underground pests, strengthen the breathing intensity and increase the seed germination rate.
3. Different varieties of bitter gourd have different resistance to powdery mildew. Generally, early-maturing varieties have weak resistance, and moderate-late-maturing varieties have strong resistance. It is necessary to pay attention to cultivating strong seedlings, rationally close planting, timely pruning and threshing, improving ventilation and light transmission conditions, and making plants Strong growth and improved disease resistance.
4, commonly used in bitter gourd powdery mildew 15% powder rust WP, or 20% rust emulsified milk 2000 ~ 3000 times liquid, or 50% carbendazim WP 500 times, or wet sulphur powder 300 times, or 75% chlorothalonil WP 600-800 times solution.
5. In the greenhouse, use bacteriostatic agent to smoke and cure downy mildew and powdery mildew. When spraying, pay attention to the spraying of the middle and lower leaves and the back of the leaves. Spray once every 7 to 10 days in the early stage of the disease. 2 to 3 times, can achieve better control effect.
Pre-planting considerations
Choose resistant varieties. Generally, early-maturing varieties are weakly resistant, and mid-late maturity varieties are more resistant.
Strengthen management. Select high-lying areas to raise seedlings, cultivate strong seedlings, sorghum cultivation, increase the application of phosphorus and potassium fertilizer, moderate water use, plastic film cultivation, reasonable close planting, ditch drainage, timely removal of diseased leaves, old leaves. Strengthen ventilation and light transmission.
Pollution-free prevention method
During the bitter gourd flowering and melon, 1000 times of potassium permanganate aqueous solution is sprayed once every 7-10 days. Or 1000 times sodium bicarbonate (sodium bicarbonate) aqueous solution, or 25-30 times grass ash leaching clear liquid. Or O.1% lime water clear liquid, etc. Even spray 3-5 times, evenly spray all the leaves to start It is advisable to drop the drops of water. If it is washed with rain within 4 hours after spraying, it should be refilled once.
Protected cultivation, 120 grams of sulfur per 50 cubic meters, 50o grams of sawdust, mix well, separate a few, or use 45% of chlorothalonil fumigant per acre for fumigation, start in the evening, fumigation 1 night, the first Open the shed for ventilation in the morning. Can cure downy mildew and powdery mildew.
Chemical control of bitter gourd powdery mildew
The disease spreads quickly and should be prevented as soon as possible. In the early stage of the disease, 50% Tsuibei dry suspension agent 3000 times solution, 40% Fuxing emulsifiable concentrate 4O00 times liquid, 10% Shigao water dispersion granules l50o times solution can be selected. 62.25% Xiansheng wettable powder 600 times solution, 15% powder rusting wettable powder 150o times solution, or 78% Cobo wettable powder 600 times solution.
25% Shi Baoke (prochloraz) emulsifiable concentrate, 4o% Schwarzkopf (pyrimethamine) suspension 10oo solution (ventilation should be ventilated after use in greenhouses, otherwise the leaves may have brown spots), 72.2% Plex (Falm) 60o ~ l000 times liquid, 30% Teflon (fluoxazole) wettable powder 3500-5000 times liquid spray, every 7 to 10 days, once every 2 to 3 times. The drug is used alternately. When spraying, pay attention to the uniform spray on the middle and lower leaves and the back of the leaves.
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