What does mildew look like on a weed plant?

Mildew, commonly known as powdery mildew, looks like a dusty white or gray coating resembling flour dusted across the leaves, stems, or buds. As the fungal infection advances, it can cause the leaves to warp, curl upward, or develop yellow and brown discolored spots, which ultimately stunts the plant's growth and compromises the harvest.

What causes mildew to grow in a cannabis grow room?

Mildew is a fungal disease that thrives in damp, stagnant environments. It is most commonly triggered by: High humidity: Environments that consistently stay above 60% relative humidity. Poor airflow: Stagnant air prevents excess moisture from evaporating and allows airborne spores to settle easily. Overcrowding: Dense, unpruned foliage creates dark, moist microclimates where leaves overlap, providing the perfect breeding ground for fungi. Temperature drops: Cool and shaded areas slow down evaporation, keeping the plant surfaces damp.

How do I prevent powdery mildew from coming back?

Prevention is always easier than treatment. To keep mildew spores from taking hold, you must eliminate the environment they need to survive. Keep your room's relative humidity strictly below 60%, especially during the flowering stage. Use oscillating fans and exhaust vents to ensure fresh air is constantly moving across the canopy. Finally, prune your plants regularly to remove excess foliage and space your pots out so light and air can reach every branch.