The GARDENA gardening expert
Your rhododendrons were obviously attacked last year by the rhododendron cicada, as a result of which the young buds were infected with a fungi which caused them to die off. The cicadas appear around June, which is why it is necessary to combat them then if necessary. The preparation Kiron by Cheminova is currently certified for the control of cicadas in house and small gardens.
Image: © Aleksey Stemmer - Fotolia