Know the crops that can become infected by powdery mildew. Although powdery mildews all look the same, they are quite different microscopically with each preferring a particular plant. This means that the powdery mildew infecting gerbera cannot infect the nearby potted roses. Unfortunately, powdery mildew can be especially troublesome on cut and potted rose, gerbera, and begonia. Poinsettia, kalanchoe, and some perennials can also become infected by specific powdery mildews.
Scout crops on a regular basis.
Unlike other diseases that are readily seen from the top of the leaf, the first colonies of powdery mildew can occur on the undersides of the lower leaves. Growers may not become aware of powdery mildew infection until the disease is well established and therefore difficult to control. Small numbers of mildew colonies become established over several days or weeks on the bottom leaves or on the undersides of leaves and remain unnoticed until the environment is favorable for rapid production of spores. Once spores are produced in great quantities, the disease spreads rapidly and becomes evident to growers. The value of scouting was demonstrated in a trial where the percentage of leaves infected with powdery mildew increased from 10 to 70 percent within a week's time under favorable environmental conditions.