|I have two gardina shrubs planted, they both flowered beautifully this year but now one has black on it. Is this a form of fungus & how should I treat it?|
The stuff you are seeing is called sooty mold. Certain pesky insects, including whiteflies, scale, or aphids secrete a substance known as honeydew, which supports the growth of the black, sooty mold.
Control the insects with sprays of an appropriate insecticide such as insecticidal soap or lightweight, horticultural oil. Direct sprays upward from beneath the plant making sure to wet the undersides of all leaves and branches. Repeat spraying will likely be necessary to get the pests under control.
When you control the pests, the sooty mold will cease to be a problem.