Frosty mildew, anthracnose, and bacterial hornblotch all have similar phenomena. The following pictures are downy mildew, anthracnose and bacterial horn blotch:

Please judge according to the pictures against each other. The following provides the corresponding prevention and control methods:

Cucumber mildew, commonly known as "running dry", "dry leaves", seedling adult plants can be victimized, mainly for the damage to leaves and stems, tendrils and pedicels are less affected. [1]? Cucumber downy mildew is the most common and most serious disease in protected cucumber cultivation. The disease is fierce, heavy, fast spreading, if not timely control, will cause devastating losses to the cucumber. Prevention and control of cucumber downy mildew is recommended from the following aspects and precautions in agricultural activities: cucumber downy mildew prevention and control should be based on prevention, prevention of the period of time according to the temperature and humidity conditions. Prevention is usually carried out before the arrival of rainy days and continuous rainy conditions. Methods can be used to prevent by spraying protective agents or using fumigants and dusts. General dosage per hectare mu 3 ~ 3.75kg, divided in the shed 4 ~ 5 places, lit and smothered shed, smoked overnight, the next morning ventilation, 5 ~ 7 days smoked once. Once downy mildew occurs, the application of pharmaceuticals for prevention and control. Pharmacy to water-based, spraying should be uniform and thoughtful, leaf positive, back evenly sprayed, focusing on the back of the leaf mold layer of the diseased leaves, in addition to the upper part of the healthy leaves for spraying protection. In addition, we should pay attention to the selection of mildew resistant seeds; strengthen the cultivation management, appropriate sparse planting, the use of raised bed cultivation: watering small water, forbidden to large water irrigation, rainy days attention to leakage, the conditions of the region using drip irrigation technology can be better control of the disease; after harvesting to thoroughly remove the disease residual leaves, and brought to the shed, outdoor proper treatment; conditions of the priority of the application of dust or smoke agent control; cucumber anthracnose in recent years the occurrence of constantly tends to be heavier, is by the introduction of the seed with bacteria. It is caused by the introduction of seeds with bacteria. It occurs in spring and fall, which is difficult to control and has a great impact on production. Cucumber anthracnose can develop from seedling to adult plant, seedling disease, more in the edge of the cotyledon leaves appeared semi-elliptic light brown spot, on the orange-yellow dotted gelatinous material; adult leaves infected with disease, the spot is nearly round, diameter of 4--18 mm, gray-brown to reddish-brown, when serious, the leaf blade dry; stem and petiole infected with disease, the spot is ellipsoidal or oblong, yellowish-brown, a little concave, when serious, the spots are connected, around the stem a week, plant withered; melon strip infected with disease, the spot is elliptic or oblong, yellowish-brown, slightly sunken, serious spots connected, around the stem a week, plant Melon strips are infected, the spots are nearly round, light green at first, then yellow-brown, the spots are slightly sunken, the surface has pink sticky material, and later cracked. Prevention: Starting from the seedling stage, spray 30ml of "Quick Pure" with 15kg of water, once in 5-7 days. Treatment: "fast net" 50 ml + "garlic oil" 15-20 ml to 15 kg of water spray, 3-5 days once, used 2-3 times. 2 prevention and control methods: 1) selection of disease-resistant varieties, such as JinYan 4 is more resistant to the disease. Select disease-free seeds or seed disinfection before sowing 2) anti-infection. Disease-free soil seedlings to prevent seedling infection. 3) Crop rotation. Crop rotation with non-melon crops for more than 3 years. 4) Cultivation and ecological control. Covering the film, reduce field humidity, timely release of wind, to avoid wounds, etc. 5) Pharmacological control,3 the implementation of raised bed mulching cultivation, control the amount of nitrogen fertilizer, increase the application of phosphorus and potassium fertilizer, spraying a variety of foliar fertilizers, to improve plant disease resistance. Remove diseased plant residues from the cultivation site at any time to reduce the source of the fungus. To carry out farming operations without dew, do not touch the plant, timely drainage after rain. Protected cultivation of cucumber, the morning temperature control at 30 ~ 33 ℃, afternoon and evening appropriate ventilation, reduce humidity to less than 70%, can inhibit the occurrence of disease; bacterial horn blotch disease is mainly harmful to leaves and melon strips. Leaf damage, the first watery light green and then become light brown, due to the restriction of leaf veins in a polygonal shape. The later lesions are gray-white and easily perforated. When humidity is high, white mucus is produced on the spots. The spots on the stems and melon strips are waterlogged at first, nearly round, and then light gray, and cracks are often produced in the middle of the spots, and fungal pus is produced when it is humid. Fruit rot in the late stage, with a foul odor.

Bacterial hornblotch early symptoms are easily confused with downy mildew and physiological water filling, should be carefully distinguished. Angular spot disease and downy mildew, the main difference is that the spot is smaller, light color, later perforation; leaf dorsal part of the disease water-soaked obviously and produce milky white fungal pus. Observed in the light, the leaf blade has a sense of light transmission. Physiological water-filled leaf dorsum appears polygonal water-soaked spots, this phenomenon mainly occurs in high ground temperature, low air temperature, especially in cloudy days, high air humidity, poor ventilation, transpiration is blocked, intracellular water seepage to the intercellular, so that the leaf surface appears as a watery stained green spots or polygonal plaques. When the sun comes out and the temperature rises, the patches disappear, leaving no trace on the leaf surface. In weakened plants, the water-damaged spots do not disappear even after the daytime temperature rises. After a few repetitions, cell death, leaf drying, or bubble disease symptoms, that is, the leaf flesh between the veins of the leaf bulge, the top of the bulge is grayish-white, or grayish-brown nearly round spots, not perforated. 1, agricultural prevention varieties selection: use of strong resistance to disease JinYan 6, summer green and other varieties. Seed treatment: save seeds in disease-free areas or on disease-free plants to prevent seeds from carrying bacteria. Seeds should be sterilized before germination. Commonly used methods are: warm soup seed soaking, soak in 50 ℃ warm water for 20 minutes; with the new Phytophthora 200 mg / kg liquid or 50% Dyson ammonium 500 times the solution of the seed 1 hour; or with formalin liquid 150 times the solution of the seed soaked 1.5 hours, then washed to germinate. 2, cultivation and management and the implementation of non-melon crops for more than 2 years of crop rotation. Utilize sterile field soil for nursery. Utilizing high ridge cultivation, laying film, reducing the frequency of watering, reducing field humidity. Protected areas are ventilated in time. Drainage in time during the rainy season. Clean the field in time to reduce the field pathogen. 3, pharmaceutical control ? Use Norwegian 86.2% Copper Master, Bordeaux liquid, oxaflatoxin pyrimethanil, carbendazim, 56% pyrimethanil chlorothalonil, metribuzin and other fungicides, 10-15 days spraying once, *** three times, alternating between the use of control. Finally before 10 am, after 4 pm, the control effect is more ideal