Azalea bark scale

Inspect hawthorn and rhododendron stems closely for small flat white or grayish scales clustered along branches, sometimes covered with fine webbing. Heavy infestations coat bark with hundreds of scales, giving branches rough encrusted appearance. Look for stems exuding sticky honeydew; sooty mold often follows, blackening stems.

Prune heavily infested branches in winter when scales are dormant. Scrub stems with soft brush to physically remove light infestations. Apply horticultural oil in March or April before new growth, coating thoroughly. If populations persist, spray again in June during crawler stage when scales are mobile and vulnerable. Preserve predatory beetles and parasitoid wasps.