Symptom Identification and Control Methods of Cucumber Phytophthora Blight
Cucumber (scientific name Cucumis sativus Linn, English name Cucumber), a plant of the genus Cucumis in the Cucurbitaceae family. Also called hu gua and qing gua. The fruit is oily green or emerald green, with soft small spines on the surface. It is widely cultivated throughout China and is now widely grown in temperate and tropical regions. Cucumber prefers warmth and cannot tolerate cold, and is one of the main greenhouse products. Cucumber was brought back to the Central Plains by Zhang Qian during the Western Han Dynasty when he was sent on a mission to the Western Regions, and was called hu gua. During the Sixteen Kingdoms period of the Five Barbarians, Emperor Shi Le of the Later Zhao tabooed the character “hu”, and the Han official Fan Tan, Administrator of Xiangguo Commandery, changed it to “huang gua”.
Morphological Characteristics of Cucumber
Annual trailing or climbing herb; stems and branches elongated, with angular grooves, covered with white stiff hairs. Tendrils slender, undivided, with white soft hairs. Petiole slightly rough, with stiff hairs, 10-16 (-20) cm long; leaf blade broadly ovate-cordate, membranous, both length and width 7-20 cm, both surfaces very rough, covered with stiff hairs, 3-5 angled or shallowly lobed, lobes triangular, toothed, sometimes ciliate at the margin, apex acute or acuminate, basal sinus semicircular, 2-3 cm wide, 2-2.5 cm deep, sometimes base connivent backward. Monoecious.
Male flowers: often several clustered in leaf axils; pedicel slender, 0.5-1.5 cm long, puberulent; calyx tube narrowly campanulate or nearly cylindrical, 8-10 mm long, densely covered with white long soft hairs, calyx lobes subulate, spreading, nearly as long as the calyx tube; corolla yellowish white, about 2 cm long, corolla lobes oblong-lanceolate, acute; stamens 3, filaments nearly absent, anthers 3-4 mm long, connective exserted, about 1 mm long.
Female flowers: solitary or rarely clustered; pedicel stout, pubescent, 1-2 cm long; ovary fusiform, rough, with small spiny protuberances. Fruit oblong or cylindrical, 10-30 (-50) cm long, yellowish green when ripe, surface rough, with spiny-tipped tuberculate protuberances, very rarely nearly smooth. Seeds small, narrowly ovate, white, without margin, both ends nearly acute, about 5-10 mm long. Flowering and fruiting period in summer.
Symptoms and Control of Cucumber Phytophthora Blight
Symptoms of cucumber phytophthora blight: when adult plants are infected, dark green water-soaked spots mainly appear at the base of the stem or at the nodes of tender stems, then become soft and constricted, and the leaves above the diseased part wilt or the whole plant dies, while the vascular bundles do not change color. When leaves are infected, large circular or irregular water-soaked spots are produced. Control measures for cucumber phytophthora blight: high-ridge cultivation, avoid flood irrigation; grafting to prevent disease; seedbed treatment, apply 25% metalaxyl wettable powder 8 grams per square meter of seedbed, mix well with soil and spread on the seedbed, and before transplanting spray the ground with a 750-fold dilution of 25% metalaxyl wettable powder.
In the early stage of the disease, spray with 72.2% Previcur SL 600-700-fold dilution, or 50% metalaxyl-copper wettable powder 600-fold dilution, or 72% Kexiu wettable powder 700-fold dilution, etc.
In addition, common diseases also include damping-off (seedling stage), brown spot disease (target spot disease), root rot, sclerotinia rot, bacterial leaf blight, bacterial wilt, soft rot, bacterial round spot disease, etc.