Powdery mildew of plants, apart from Erysiphe cichoracearum can caused by other genus of epiphytic parasites such as Leveillula,Sphaerotheca,Podosphaera, depending on the host. Powdery mildew in Curcubitaceae is found that caused also by the pathogen Podosphaera xanthii. E. cichoracearum is an ectoparasite which means that the fungi grows on the surface of the leaf and doesn’t penetrate the plant tissue as L.taurica (endoparasitic fungi) does. Pathogen’s spores dispersed via wind and rain water. Despite that Powdery mildew pathogens are more common in cold/hot areas with enough humidity, severe damages take place in hot and dry climates, because pathogens spores(conidia) can germinate even without humid conditions on the leaf surface. If not treated efficiently, it can destroy the entire crop. The pathogen can survive in volunteer plants in the field or in greenhouse and in healthy cultivated plants. The symptoms of the disease can progressively reduce the quality and quantity of crop production.
Leaves: Rounded, white spots/lesions on the upper and lower leaf surface with the typical powdery fungal growth. In optimum conditions, the whitish, powdery fungal growth can occupy the whole leaf surface and an important part of the stem. Sometimes small black specks can appear on the fungal growth called chasmothecia . That leads to leaf death.
Stem: Covered with white powdery fungal growth. Stunted appearance
Fruits: Sometimes, the typical powdery growth may appear on fruit surface
Hosts: watermelon, zucchini, cucumber, potato, okra, melon, pumpkin
“Vegetable diseases” – Panagopoulos G.C.
University of Massachusetts Amherst