Pacific West Botanicals From Planting Instructions: under Pests and Diseases Rust Fungus One type loves roses, and another hollyhocks, snapdragons etc. Each type rust is specific to certain plants. Non transferable to other species. On roses normally late spring yellow to orange pustiles on underside of older leaves. Other rust types are brownish or purple. Infection progresses on leaf undersides to powdery masses of spores and upper surfaces display yellow mottling. Advanced stages - entire leaves may turn yellow and drop. Warm days, cool nites, and moisture ( heavy dew ) will encourage rust development, rain, sprinkling and wind spread to other plants. Leaf surfaces must be wet for minimum of 4 hours for rust to germinate and infect. Prolonged hot, dry weather will halt rust development. Can survive overwinter on both live and dead leaves. Prevention begins in winter. Thoroughly clean up fallen leaves and debris and remove infected leaves on plants. Could spray in season with fungicides ( wettable sulfur ). Water overhead only on sunny mornings so leaves dry quickly. |