Moldy weed usually has a musty or sour smell and a fuzzy or slimy texture. It may also have white, gray, black, green, yellow, or brown spots on the surface or inside the buds. Moldy weed can be harmful to your health if smoked or ingested as it can cause respiratory infections, allergic reactions, or poisoning. If you suspect that your weed is moldy, do not use it and dispose of it safely.