Common problems of Rhododendron L. in the Central Botanical Garden of the National Academy of Sciences of Belarus

Abstract

Rhododendrons are some of the most attractive flowering shrubs in the landscape. The article presents the results of studying the common problems of Rhododendron collection in the Central Botanical Garden of the National Academy of Sciences of Belarus, conducted in 2012-2020. There are several diseases and pests that commonly occur on rhododendrons every year. These include powdery mildew (Erysiphe azaleae), fungal leaf spots (Pestalotiopsis rhododendri, Colletotrichum gloeosporioides, Alternaria spp., Sphaerulina azaleae, Phyllosticta concentrica, Phyllosticta rhododendricola), black vine weevil (Otiorhynchus sulcatus), garden foliage beetle (Phyllopertha horticola), click beetle (Hemicrepidius niger), red spider mite (Tetranychus urticae), physiological leaf spots, oedema, winter injury, chlorosis. Less common on rhododendrons are stem diseases (Botryosphaeria dothidea, Cadophora spp., Hymenoscyphus spp.), wilt (Fusarium oxysporum), bud blight (Seifertia azaleae), leaf and flower gall (Exobasidium rhododendri), rhododendron lacebug (Stephanitis rhododendri), greenhouse whitefly (Trialeurodes vaporariorum). There were identified that all evergreen and half evergreen rhododendrons have some resistance to powdery mildew, deciduous rhododendrons are more resistant to fungal leaf spots than evergreens. Damage to rhododendrons by insect pests usually does not cause significant harm but heavy feeding results in an unsightly plants.