I would've never thought to use river rock at the base of potted plants/at the edges of the patio, but maybe that could work. A larger, flat top rock could even act as a riser for a led candle lantern, etc.
Diseases of Plant Leaves. This picture describes the graphical detail of plant leave disease. White Flies Aphids Spots Grey Mould Powdery Mildew Leaf Fall Leaf Bronzing Rust Mealy Bug Yellowing of Leaves garden-organic-self-sustain