FLOURING in CUCURBITACEAE - Sphaerotheca fuliginea
Symptoms of the disease (characteristics for the diagnosis of the disease)
- The disease affects all above-ground parts of the plants, covering their surfaces with a whitish, powdery layer composed of fungal mycelium and fruiting bodies. On the leaves, it appears on both sides, though more commonly on the upper surface, as circular or irregular whitish, powdery spots. Initially small (6-10 mm in diameter), these spots are scattered unevenly across the leaf surface.
- As the infection progresses, the spots gradually expand and merge, covering large sections of the leaf, or sometimes the entire leaf surface. Initially, the affected tissue appears healthy, but over time it browns and dries out. A whitish, felt-like layer also develops on petioles, tendrils, and stems, often encircling these structures completely. By the end of the growing season or sooner, as the leaves begin to wither numerous blackish-brown dots, known as the fungus's perithecia, emerge within the mycelial layer.
Factors favoring the occurrence and evolution of the disease, its transmission and spread
- The evolution of the disease is directly influenced by the vegetation phase, temperature and atmospheric humidity. Humidity has a secondary role, because the reproduction of the fungus also takes place in dry conditions, at relative humidity of (40-50%).
- Infections intensify as atmospheric humidity increases, but do not occur when the surface of the leaves is covered with a film of water.
- Regarding temperature, conidia formation and penetration into host plant tissues have been found to occur between 10 and 53ºC, and the optimum temperature is between 20 and 28ºC.
Prevention and control measures
When the attack is signaled, foliar treatments with products based on Penconazole (Topaz 100 EC 0.03% with a 3-day break) will be carried out; Folpet + Triadimenol (Shavit F 72 WDG 0.2%); Metiram + Pyraclostrobin (Cabrio Top 0.15-0.2%);
Azoxystobin (Ortiva Top 0.1% in the second part of the vegetation period; Mirador 250 SC 0.075%).
Propiconazole (Bumper 250 EC 0.015%); Difenoconazole + Ciflufenamide (Cidely Top 0.1%); Sulfur (Thiovit jet 0.5%, Kumulus DF 0.4%); Meptildinocarp (Karathane gold 350 EC 0.05%); Myclobutanil (Systhane Forte 0.02%), Isopyrazam (Reflect 0.1%.).
Ecological products applied foliar:
Mimox 0.2-0.3%, applied alone or mixed with Copfort; Special Microthiol 0.4% is effective against pathogens that produce powdery mildew on cucumbers and melons and lends itself to integrated control schemes for these crops.
Foliar biostimulators for the prevention of factors favoring the appearance of the disease: AXEKELP PLUS (0.3%), AXEMIN PW40 (0.3%)
