How to Manage Pests

Pests in Gardens and Landscapes

Rhododendron species resistant to feeding by adult root weevils.*
Species Series Possible Bloom Colors Rating*
heliolepis Heliolepis white, rose 100
impeditum Lapponicum purplish blue 100
scintillans Lapponicum purplish blue 100
burmanicum Maddenii yellow to greenish white 100
dauricum Dauricum lavender-rose 97
intricatum Lapponicum mauve 97
desquamatum Heliolepis rose, violet 93
ferrugineum Ferrugineum rose, white 93
hemsleyanum Fortunei white 93
minus Carolinianum rose, white 93
cuneatum Lapponicum rose 90
fastigiatum Lapponicum lilac, purple 90
yakusimanum Ponticum white, rose 90
ungernii Ponticum white, pale pink 83
rubiginosum Heliolepis pink, rose 83
irroratum Irroratum white, ivory, rose 83
carolinianum Carolinianum pink, mauve, white 80
oreodoxa Fortunei rose, white 80
racemosum Virgatum white, rose 80
russatum Lapponicum blue-purple 80
adenophorum Taliense rose 77
campylogynum Campylogynum pink, purple, crimson 77
oreotrephes Triflorum mauve, purple, rosy red 77
vernicosum Fortunei white, rose 77
xanthocodon Cinnaborinum ivory, yellow 77
arizelum Falconeri white, yellow, rose, crimson 73
cardiobasis Fortunei white, rose 73
decorum Fortunei white, pink, chartreuse 73
diaprepes Fortunei white, pale rose 73
eurysiphon Thomsonii ivory, rose 73
glaucophyllum Glaucophyllum white, rose 73
hippophaeoides Lapponicum lilac, rose 73
lepidastylum Trichocladum pale yellow 73
pemokoense Uniflorum lilac-pink 73
praestans Grande magenta-rose, pink 73
pubsescens Scabrifolium white, rose 73
imperator Uniflorum pink, rose 70
ciliatum Maddenii white, rose 70
concatenans Cinnaborinum apricot, yellow 70
davidsonianum Triflorum white, pink, rose 70
discolor Fortunei white, pink 70
yunnanense Triflorum white, lavender, pink 70

*The higher the number, the less feeding is expected. A 100 rating indicates complete resistance to black vine weevil (Otiorhynchus sulcatus), clay-colored weevil (Otiorhynchus singularis), Dyslobus species, obscure root weevil (Sciopithes obscures), and woods weevil (Nemocestes incomptus).

Source: Antonelli AL, Campbell RL. 2007. Root Weevil Control on Rhododendrons. Washington State University Extension Bulletin 0970E.

Statewide IPM Program, Agriculture and Natural Resources, University of California
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