What is Podosphaera xanthii? Podosphaera xanthii is a pathogenic fungus which causes “powdery mildew” on plants, especially cucurbits. The naming of this fungus is not standardized, and you may also know it as Podosphaera fusca, Sphaerotheca fuliginea or Sphaerotheca fusca. In addition to P. xanthii, powdery mildew is caused by many other fungal species including in the genera Erysiphe, Microsphaera, Phyllactinia, Sphaerotheca, Uncinula and Leveillula, making it difficult to pinpoint the causative agent of powdery mildew.
Cucurbits – family of plants which includes pumpkins, squash, cucumbers, gourds, watermelons and cantaloupe
Powdery mildew is attributed to 30-50% crop loss in cucumbers and over 40% crop-off in mungbeans. It is also a problem in other crops, including hydroponically grown fruits and vegetables such as lettuce.
Infection and Symptoms
Infection with powdery mildew disease occurs when spores, called conidia, land on the plant (typically on the leaf surface) and form small strands that enter the plant’s epidermal cells. Once inside the plant, long strands called hyphae develop, which, when combined with the conidia (spores), create the distinct white coating on the plant surface . These spores typically spread through airborne transmission but can also spread through direct contact with contaminated objects/surfaces.