Characterisation and pathogenicity of Ditylenchus dipsaci isolated from Phlox subulata in Japan

Moss phlox, Phlox subulata L., commonly known as ‘Shiba zakura’ (turf cherry), is one of the most important ornamental plants in Japan. Since 1956, thousands of visitors have gathered each spring in different prefectures to enjoy the beauty of this Phlox as part of a traditional festival. Recently, foliage dieback symptoms were observed in Phlox from many parks in the Chubu area of Japan, causing significant commercial losses (Fig. 1A-C). Dieback is a common symptom caused by Ditylenchus dipsaci (Kuhn) Filipjev (Hooper, 1972), which primarily infects onion and garlic but can also occur in many flowering plants, including Phlox, and is a quarantine species (Jones et al., 2013). The occurrence of this nematode in Japan is well documented on onion, narcissus, lily, tulip and hyacinth (Inagaki, 1985; Katsunori, 1987), but has never been documented on Phlox, although D. dipsaci was reported in 1993 by the Hokkaido Plant Protection Office (unpubl.). Herein, we report the first confirmed occurrence of D. dipsaci on Phlox from the Chubu area of Japan, the nematode identity being confirmed through morphological, molecular and phylogenetic methods. This finding is of quarantine importance for other areas of Japan.