Powdery mildew is a white powdery growth that forms on the surface of the cannabis leaves. The fungus first appears as small bumps on the upper side of the affected leaves, and if left unchecked it can extend to the petioles, stems and finally the buds, completely destroying the resin and crippling the plant entirely. Also known as Oidium or White Mold, the pest affects both indoor and outdoor cannabis. It is necessary for farmers to take preventative measures from the beginning to keep powdery mildew at bay.
Merriam-Webster Online Dictionary
powdery mildew (noun)1.
an ascomycetous fungus (family Erysiphaceae) producing abundant powdery conidia on the host
2.
a plant disease caused by a powdery mildew
White Mold, Fungal Growth, Mildew Fungus, Plant Fungus, Powdery Fungus