What are the symptoms of cucumber powdery mildew? Detailed explanation of control methods
Cucumber powdery mildew is one of the common diseases in cucumber cultivation and occurs all over the country. Because powdery mildew has developed a certain degree of resistance to fungicides in recent years and can occur in all four seasons, control has become somewhat difficult. Therefore, in ordinary years yield loss is about 10%, and in epidemic years yield loss is about 20-40%. Let us take a look together at how to control cucumber powdery mildew!
Symptoms of cucumber powdery mildew
In cucumber powdery mildew, leaves suffer the most severe damage, followed by leaf stalks and stems; fruit is generally not affected. In the early stage of the disease, small nearly round white powder spots appear on the upper or lower surface of the leaves, gradually expanding into large white powdery areas with indistinct edges, covering the leaf surface as if a layer of white powder had been sprinkled on it. Wipe away the white powder and the leaf surface can be seen to be chlorotic, withered yellow and brittle. When the disease is severe, the leaf surface is covered with white powder and turns grayish white, until the entire leaf dies. After powdery mildew infects leaf stalks and tender stems, the symptoms are similar to those on leaves, except that the lesions are smaller and there is less powdery material. On the leaves, small yellow spots first appear, then expand and develop into round or oval lesions, with a white powdery mold layer on the surface.
Factors contributing to cucumber powdery mildew
1. High planting density and poor ventilation and light penetration lead to severe disease; applying too much nitrogen fertilizer causes overly tender growth, reduced resistance and easy onset of disease.
2. Heavy, acidic soil, many years of continuous cropping, large amounts of diseased plant residues in the field, insufficient fertility, extensive cultivation, and weed-infested plots reduce plant resistance and lead to severe disease.
3. Fertilizer that is not fully decomposed, organic fertilizer carrying pathogens, or fertilizer mixed with diseased residues of crops in the same family easily leads to disease.
4. Warm climate, dry air, constant alternation of drought and humidity, and insufficient light easily lead to disease; long periods of dryness after continuous rainy days also easily lead to disease.
How to control cucumber powdery mildew?
1. Choose plots with good ventilation, loose and fertile soil, and convenient drainage and irrigation for planting. Appropriately apply phosphorus and potassium fertilizer in combination to prevent nutrient deficiency and premature aging, and enhance plant disease resistance. Do not water on cloudy days, ventilate more on sunny days, reduce the relative humidity of the greenhouse or plastic tunnel, and prevent excessive temperature so as to avoid muggy heat. In the early stage of cucumber powdery mildew or before the disease occurs, mainly use protective fungicides to prevent infection and onset of the disease.
2. When powdery mildew damage symptoms appear on leaves in the field, attention should be paid to using fast-acting therapeutic fungicides, and an appropriate amount of protective fungicide should be added for rational mixing to prevent the disease from further worsening and spreading. Experience shows that when powdery mildew occurs, small amounts of water can be poured between cucumber rows to increase air humidity, and combined with spraying, the disease can be controlled at one stroke. Supporting measures also include avoiding excessive application of nitrogen fertilizer, increasing application of phosphorus and potassium fertilizer, and clearing diseased plant residues after pulling up the vines.
3. Spray in time in the early stage of the disease. You can use 25% azoxystrobin suspension concentrate at 1500 times dilution, or 10% difenoconazole water-dispersible granules at 2000 times dilution for prevention. When spot patches occur, immediately spray 32.5% difenoconazole · azoxystrobin suspension concentrate at 1500 times dilution, or 25% triadimefon emulsifiable concentrate at 3000 times dilution, or 6% fenarimol wettable powder at 1500 times dilution, or 50% kresoxim-methyl water-dispersible granules at 3000 times dilution, or 12.5% diniconazole wettable powder at 2000 times dilution, or 33.5% quinolinone suspension concentrate at 800 times dilution, or 8% flusilazole microemulsion at 1200 times dilution, or 30% nonyl copper microemulsion at 400 times dilution.
Cucumber powdery mildew pictures, cucumber powdery mildew control
Cucumber powdery mildew has been a major disease in recent years, causing large-scale yield reduction of cucumber crops. Farmer friends should promptly learn about cucumber powdery mildew pictures and cucumber powdery mildew control.
Symptoms of cucumber powdery mildew: leaves suffer the most severe damage, followed by leaf stalks and stems; fruit is generally not affected. In the early stage of the disease, small nearly round white powder spots appear on the upper or lower surface of the leaves, gradually expanding into large white powdery areas with indistinct edges, covering the leaf surface, withering yellow and becoming brittle. When the disease is severe, the leaf surface is covered with white powder and turns grayish white, until the entire leaf dies. After powdery mildew infects leaf stalks and tender stems, the symptoms are similar to those on leaves, except that the lesions are smaller and there is less powdery material. On the leaves, small yellow spots first appear, then expand and develop into round or oval lesions, with a white powdery mold layer on the surface. Under normal conditions, there are more on lower leaves than on upper leaves, and more on the underside of leaves than on the upper side. In the early stage, the mold spots are separate and scattered, then merge into one large mold spot and can even cover the whole leaf, seriously affecting photosynthesis, disturbing normal metabolism, causing premature aging and yield loss.
Factors contributing to cucumber powdery mildew: it can parasitize host plants year-round and become the primary infection source. The optimum temperature for the onset of this pathogen is 20-25°C, and it is not strict about relative air humidity; under conditions of about 25% relative air humidity, the disease can also occur and become epidemic. When conditions are suitable the following year, conidia germinate and spread to host leaves with the aid of airflow or rainwater. After 5 days, white mycelium-like lesions form, and after 7 days they mature, forming conidia that disperse and spread, causing re-infection. Cucumbers cultivated in protected facilities are more severely affected because of poor ventilation, excessively high planting density, excessive nitrogen fertilizer application, and low-lying plots.
Cucumber powdery mildew pictures, cucumber powdery mildew control: when powdery mildew damage symptoms appear on leaves in the field, attention should be paid to using fast-acting therapeutic fungicides, and an appropriate amount of protective fungicide should be added for rational mixing to prevent the disease from further worsening and spreading. For prevention before the onset of cucumber powdery mildew, spray 27% high-lipid film at 80 times dilution; in the early stage of the disease, use 2% pyrimidine nucleoside antibiotic agricultural antibiotic at 200 times dilution, duoyangqing at 600 times dilution, or 10% shigao water-dispersible agent at 1500 times dilution for foliar spraying. You can choose 50% thiophanate-methyl wettable powder at 1000 times dilution, or 75% chlorothalonil wettable powder at 500-600 times dilution, or 56% azoxystrobin chlorothalonil at 600 times dilution, spraying once every 5-7 days for therapeutic effect.
The above are cucumber powdery mildew pictures and cucumber powdery mildew control; farmer friends should apply fungicides promptly for control so that cucumber crops can resume growth.
Factors contributing to cucumber powdery mildew and key points of control
Cucumber powdery mildew generally mainly harms leaves, while stems, leaves and fruit are less affected. Therefore, when treating cucumber powdery mildew, people should clearly understand the main locations harmed by powdery mildew so that they can prescribe the right remedy. Today the editor will introduce to you the factors contributing to cucumber powdery mildew and the key points of control:
Factors contributing to cucumber powdery mildew
1. High planting density and poor ventilation and light penetration lead to severe disease; applying too much nitrogen fertilizer causes overly tender growth, reduced resistance and easy onset of disease.
2. Heavy, acidic soil; many years of continuous cropping with large amounts of diseased plant residues in the field; insufficient fertility, extensive cultivation, and weed-infested plots reduce plant resistance and lead to severe disease.
3. Fertilizer that is not fully decomposed, organic fertilizer carrying pathogens, or fertilizer mixed with diseased residues of crops in the same family easily leads to disease.
4. Warm climate, dry air, constant alternation of drought and humidity, and insufficient light easily lead to disease; long periods of dryness after continuous rainy days also easily lead to disease.
Key points of cucumber powdery mildew control
1. Eradicate the pathogen: in combination with field management, promptly prune diseased leaves and old leaves on the lower part of diseased plants, improve the environmental conditions inside the greenhouse, and cut off the transmission route.
2. Select suitable pesticides and carry out chemical control well. You can choose 50% thiophanate wettable powder, or 20% triadimefon emulsifiable concentrate at 2000-3000 times dilution, or diniconazole wettable powder at 3000-4000 times dilution. Generally use 50-70 kg of spray solution per mu, spraying once every 7-10 days. Note that different agents should be used in rotation to prevent resistance. Spray 3-4 times continuously. When spraying, spray the upper and lower surfaces of the leaves evenly.