Poster Session: Diseases of Plants - Disease Detection and Diagnosis

363-P

Diseases and pests are threatening boxwood in Scandinavian landscape plantings.
V. Talgø (1), C. Magnusson (1), I. M. Thomsen (2), H. P. Ravn (2), G. M. STRØMENG (3)
(1) Bioforsk Norwegian Inst of Agric & Env Res, Aas, Norway; (2) University of Copenhagen, Frederiksberg C, Denmark; (3) Bioforsk, Ås, Norway

During the last decade, several disease and pest problems have occurred on boxwood (Buxus sempervirens) in Scandinavia, likely due to increased trade of symptomatic or latently infected plants. There are clear evidences that imported, infected plants have been distributed. Leaves and shoots on boxwood are damaged by the fungi Volutella buxi (Volutella leaf and stem blight) and Cylindrocladium buxicola (boxwood blight), the latter is also associated with death of whole plants. In Denmark, the insects Psylla buxi (boxwood psyllid) and Monarthropalpus buxi (boxwood leaf miner) are commonly found on damaged leaves, but more serious are the injuries caused by the boxwood nematode, Rotylenchus buxophilus. In 2013, very high densities of this nematode were detected on dying boxwood plants in a baroque garden in Copenhagen. The soil contained up to 60 times more R. buxophilus than the damage threshold. A Rhizoctonia sp. was isolated from the dying roots, but no Phytophthora spp. or other serious root pathogens were found. In general, parasitic nematodes are known to wound roots and thereby make entry points for pathogens, among them Rhizoctonia spp. In 2013, R. buxophilus was detected in symptomatic boxwood from Sweden. It was also found in containerized, seemingly healthy, imported plants in Oslo, but not on boxwood from a nursery in southern Norway.