Morphology and prevention methods of powdery mildew of wax gourd

Today I will tell you about the symptoms of winter melon powdery mildew and how to better prevent and treat it:

Morphological characteristics of the pathogen of wax gourd powdery mildew

Erysiphe cucurbitacearum Zheng & Chen called it powdery mildew of cucurbitaceae and Sphaerotheca cucurbitae (Jacz.) ZYZhao called it single capsule of melon, both belong to Ascomycota fungi. E.cucurbitacearum mycelium grows on both sides of leaves. There are irregular dirty white powdery patches, which later fuse with each other; conidia barrels are columnar or nearly columnar, with a size of 17.8-27.9×12.2-15.2 microns; ascocarps are mainly grown on the back of leaves, oblate, aggregated, dark brown, with a diameter of 85-137 microns, mostly 95-122 microns, wall cells are irregular polygonal, with a diameter of 6.3-20.3 microns, with 17-56 appendages, generally unbranched, a few are irregularly branched once or 1-2 times, curved, 45-250 microns long, and some reach 3-15 microns, 0.5-2 times the diameter of the ascocarp, uneven in thickness, some thin at the top and slightly wider at the bottom, 3.0-10.2 microns wide, mostly 5.1-7.6 microns, thin and smooth wall, with 0-6 septa, brown, gradually light in the middle upwards; 5-13 asci, mostly 7-11, long ovate to oblong or ovate to elliptical or other irregular shapes, with stalks or short stalks, some nearly sessile, size 48.3-68.6×25.4-35.6 microns; 2 ascospores, ovate, yellowish, size 18.8-22.9×12.5-15.2 microns. For the morphological characteristics of S.cucurbitae, please refer to the watermelon powdery mildew pathogen. W.R.Sitterly combined reports from all over the world and believed that melon powdery mildew fungi belong to 3 genera and 6 species. They are Erysiphe cichoracearum DC ex Mecat, E. communis (Wallr.) Link, E. polygoni (DC) St.-Am., E. polyphaga Hammarl., Leveillua tauHca (Lev.) Arnaud and Sphaerotheca/kliginea (Sehlecht et Fr.) Poll. In the Chinese Fungi, the Powdery Mildew Order believes that the main powdery mildews of melons in my country are E. cucurbitacearum Zheng and Chen and S. ccucurbitae (Jacz.) ZYZhao. However, some experts believe that the main powdery mildews of melons in my country are S. fuliginea (Schlecht ex Ff.) Poll and E. cichorocearum DC. and S. humuli (DC.) Burro. The powdery mildews of S. fuliginea and S. humuli (DC.) Burro are widely distributed, while S. humuli are less common.

Transmission routes and disease conditions of wax gourd powdery mildew

Powdery mildew can overwinter on roses or melon crops or diseased residues in greenhouses and greenhouses, becoming the source of infection in the early next year. Field reinfection is mainly caused by conidia produced after the disease is spread by air currents or rain. Because this fungus reproduces very quickly, it is easy to cause an epidemic.

Powdery mildew can occur at temperatures between 10 and 25°C. Whether it can spread depends on humidity and the growth of the host. It can germinate at low humidity, and the germination rate is significantly increased at high humidity. Therefore, the spread of powdery mildew is accelerated when the weather is dry after rain, or when there is little rain but the field humidity is high. Higher humidity is conducive to spore germination and invasion. High temperature and dryness are conducive to conidia reproduction and disease spread, especially when high temperature and drought alternate with high humidity conditions, and there are a large number of powdery mildew and susceptible hosts, the disease will spread. Powdery mildew conidia can fully germinate at low humidity of about 45%. On the contrary, when dew condensation on the leaves lasts for a long time, the growth and development of the pathogen is inhibited. [2]

Methods for controlling powdery mildew of wax gourd

(1) Select disease-resistant varieties. Select early- to mid-maturing winter melon varieties such as Guangyou No. 1 and Huidou, or mid- to early-maturing varieties such as Guangyou No. 2, Guanxing No. 2, and Qixingzai.

(2) At the early stage of the disease, spray 100-150 times of Nongkang 120 or Wuyijinsu water solution, once every 7-10 days, and control 2-3 times continuously. In addition to controlling powdery mildew, it can also control anthracnose, gray mold, black spot, etc. At the early stage of the disease, you can also spray 20% triadimefon (triadimefon) emulsifiable concentrate 2000 times or 60% anti-mold treasure No. 2 1000 times, 15% Zhuangyuanle water solution 200 times, 6% Lebigen wettable powder 1000-1500 times, 12.5% ​​Subaoli wettable powder 2500 times, 5% Santailong wettable powder 2000 times, 30% white pine emulsifiable concentrate 2000 times. In areas where the above-mentioned fungicides are resistant, you can use 8,000 to 10,000 times dilution of 40% Fuxing emulsifiable concentrate, once every 20 days or so. After one control, you can switch to commonly used fungicides.

(3) For winter melon and wax gourd grown in greenhouses, 5% chlorothiazide dust remover can also be used, 1kg per 667m2. Stop using the drug 7 days before harvesting. The key points of the technology are early prevention, prevention before noon, thorough spraying and large amounts of water.