What's eating my williams rhododendron?

Williams rhododendron is susceptible to vine weevil, lace bug, and scale insects in common with other garden rhododendrons. Notably, its naturally curled leaf margins can mechanically deter vine weevil adults from biting. UK-grown plants also face the rhododendron leafhopper. Good siting in dappled shade reduces most pest pressure.

Adults nibble notched bites from leaf margins; larvae attack roots causing wilting. Container plants are most at risk from root-feeding grubs. Apply beneficial nematodes (Heterorhabditis spp.) to moist compost in late summer. Check containers regularly for white C-shaped larvae. Biological or chemical vine weevil treatments are most effective in pots.

Yellow stippling on upper leaf surfaces and dark excrement spots underneath. Worst on plants in full sun, causing a bleached, washed-out appearance. Spray leaf undersides with insecticidal soap or neem oil in spring. Systemic imidacloprid soil drench provides season-long control. Site in partial shade to reduce susceptibility.

Egg-laying punctures in flower buds allow bud blast fungus to enter, causing buds to brown and die before opening. Adults are colourful and visible from midsummer. Spray adults with a pyrethroid insecticide July through October. Remove and destroy blasted buds. Avoid conditions that favour leafhopper — dense, humid plantings.