What are the pests and diseases for a rhododendron?
Rhododendrons are susceptible to fatal root diseases caused by honey fungus (Armillaria species) and Phytophthora species. Honey fungus spreads between the bark and wood of the roots, and decays the plant tissue. When it reaches the root collar and girdles it, the plant dies. Honey Fungus will kill other tree & shrub species it is no respecter of boundaries. As will Phytophthora. The organisms that cause Phytophthora root rot are microscopic and fungi-like, killing roots and sometimes spreading up stems to form an inverted V-shaped lesion (left). Above ground, symptoms of both are similar; progressive dieback or sudden wilting and plant collapse, depending on the speed of infection. In either case, little can be done. Remove and destroy the infected root systems and, in the case of Phytophthora (which is water-borne), improve drainage around plants. Powdery mildews In evergreen rhododendrons these fungi attack leaf undersides, causing patches of discolouration. In deciduous species whi
