In most instances the speckled silvering leaves are caused by Azalea Lace Bug (Stephanitis pyrioides). Other problems in Rhododendron spp. include Azalea leafminor, powdery mildew, greenhouse thrips, whiteflies, two-spotted mite, leaf gall, petal blight, grey mould, phytophthora root rot and sunburn.
Lace bugs are sap sucking insects that congregate on the underside of leaves, a small number of these insects will not kill a plant and does not necessarily require treatment.
As with most tree pest and diseases problems it is important to ensure the plant is appropriate for the area and plant health issues are addressed. Ensure adequate water and soil condition and protection from severe weather. Both azaleas and Rhododendron’s generally prefer protection from full sun.
Treetec can help with advice and treatments for Azalea Lace Bug as well as other problems. Timing of chemical treatments is critical.
Rhododendron leaf damage