Powdery Mildew

Definition - What does Powdery Mildew mean?

Powdery mildew is a fungal disease that affects a wide range of plants, including cannabis plants. This disease is caused by multiple different species of fungi in the order of Erysiphales, with Podosphaera xanthii (a.k.a. Sphaerotheca fuliginea) being the most commonly reported cause. Erysiphe cichoracearum was formerly reported to be the primary causal organism throughout most of the world.

Powdery mildew is one of the easiest plant diseases to identify because the symptoms shown are quite distinctive. Infected plants display white powdery spots on the leaves and stems. The lower leaves are the most affected, but the mildew can appear on any above-ground part of the plant. As the disease progresses, the spots get larger and denser as large numbers of asexual spores are formed, and the mildew may spread up and down the length of the plant.

Hydrolife explains Powdery Mildew

Powdery mildew is caused by a variety of fungi resulting in the appearance of a white or gray powdery growth on leaves. The same species that attack hops also attack marijuana plants. Powdery mildew can appear on the plants anywhere, whether they are grown indoors or out. Before the powder forms, small bumps may be noted on the topside of affected leaves.

Mildew spores are carried by the wind, air ventilation systems, clothing, pets, and just about any living thing that moves about. These mildew spores will remain dormant until environmental factors offer the optimal conditions for them to come to life. Powdery mildew is most likely to occur when humidity levels exceed 55% and temperatures are warm.

Once awakened, the powdery mildew spores are likely to attack the young plants first and then will spread over the entire plant, infecting stems and buds, in addition to leaves.

Some risk factors for powdery mildew include overwatering, getting the leaves of the plant too wet, improper ventilation that results in high humidity (humidity over 55%), and rain.

Powdery mildew can also occur in young plants that aren’t yet well-established, and when plants are overcrowded in general and end up trapping moisture within the plant canopy.

There are plenty of remedies on the market to help growers eradicate and prevent powdery mildew from their grow rooms.

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