By Melinda MyersGuest ColumnistWhether gardening indoors or outdoors, gardeners are likely to encounter powdery mildew on one or more of their plants. As the powdery mildew expands and covers the leaves, it blocks sunlight from reaching the leaves inhibiting photosynthesis. Different species of powdery mildew fungi attack different plants. If the weather conditions are right and the various fungi are present, gardeners may find powdery mildew on a variety of plants in their landscape or indoor garden. Watch for powdery mildew on azaleas, crabapples, dogwoods, lilacs, photinia, roses, coral honeysuckle vines and other trees, shrubs and vines.