How can one identify powdery mildew?

Unfortunately, you cannot remove it - you can just keep it at bay with the sprays etc. If you want to remove it, you have to remove ALL plants that are affected then start over. It is important to make sure the environment you put the new plants in is clean and has been treated for the fungi. It's also important to keep the growing environment unfavorable for the disease - this means relative humidity at 50-60% or lower, and temperatures warmer than 75-80 degrees F.