Rhododendron racemosum · Shrub
Vine weevil: Apply nematodes to moist soil in autumn or use a systemic insecticide for severe infestations.
Rhododendron budworm: Prune out affected shoots or apply a biological insecticide like spinosad when larvae emerge.
Powdery mildew: Improve air circulation and spray with a fungicide containing myclobutanil if severe.
Phytophthora root rot: Ensure well-drained acid soil and avoid overwatering; remove severely infected plants.
Pieris lacebug: Spray with a horticultural oil or insecticidal soap during early summer outbreaks.