Powdery Mildew and Mold are two things you never want to see turn up in your garden. Indoor gardens rely very heavily on contained moisture and regulated humidity. This moist environment can easily become a breeding ground for molds and mildews. Not only can these molds and mildews cause damage to your plants, they can become a health problem if left unchecked.
If you find mold or mildew growing on your plants, rockwool or in the nutrient solution, the first thing that you should check is the humidity and air circulation in your indoor garden. Stagnant air allows mold and mildew spores to settle on the plants, and an overly humid environment allows them to thrive. For mild infestations, these changes may be enough to reverse the infestation, and ensure healthy plants. If the mold or mildew growth is heavy, you may need to employ a fungicide to remove the growths.
While prevention should be the number one plan of attack there are a few things that you can do if powdery mildew or mold does strike your garden. Fungicides are a great option to fight these garden monsters but they can be a tricky proposition in any garden. Fungicides are powerful chemicals that can burn or destroy a plant if used in a manner inconsistent with the labeling. In an indoor garden, though, one misplaced spray can contaminate your entire nutrient solution, damaging or even potentially killing your plants. If you do find yourself in need of a fungicide, make sure you get one that is specially designed for use in an indoor garden, and follow the directions carefully.
To avoid further spreading of powdery mildew and mold in your garden you must be extra carful when taking care of your plants. Pruning and rotating crops is enough agitation for the mold and mildew to shake off of one plant and land on another. If a plant is totally covered in powdery mildew or mold then I suggest you cut your loses and remove it completely from your garden. Removing the plant will help contain any further spread of mold and mildew. Lastly it is extremely important to clean and sterilize everything especially after rotating crops or replacing components!