The RHS believes that avoiding pests, diseases and weeds by good practice in cultivation methods, cultivar selection, garden hygiene and encouraging or introducing natural enemies, should be the first line of control. If chemical controls are used, they should be used only in a minimal and highly targeted manner.
- Clipping evergreen hedges so that they taper outwards towards the bottom can help improve light access to the base
- Congested evergreen shrubs should be thinned out at the appropriate time of year to increase air circulation around the leaves. This will allow rain to dry more quickly on wetted foliage and reduce the opportunity for algae to build up
- Feeding straggly plants in the spring to encourage vigour should also help
There are no chemical controls for algae on plants.