Rhododendron arboreum · Shrub
Powdery mildew: Tolerate unless severe; improve air circulation and avoid overhead watering to reduce humidity.
Bud blast: Remove and destroy infected buds promptly if practical; ensure good drainage and avoid late pruning.
Vine weevil: Apply biological nematodes to the soil in autumn or use physical barriers like sticky bands.
Rhododendron leafhopper: Encourage natural predators like ladybirds; use insecticidal soap for severe infestations.
Pieris lacebug: Prune out heavily infested shoots; apply horticultural oil or insecticide if populations are high.