Devibursaphelenchus alienae n. sp. isolated from the bark of dead Quercus aliena in Japan

Summary A new Devibursaphelenchus species isolated from the bark of a dead Quercus aliena, which had been infected and killed by Japanese oak wilt, was collected in Shiga, Japan. The new species is characterised by the relatively large body in males (661-768 μm) and females (893-1071 μm), conspicuous male bursal flap, male spicule with long condylus and wide blade, female post-vulval uterine sac (PUS) 39-54 μm or 1.6-2.3 times the vulval body diam. long, vestigial female anus, and female tail forming a strongly ventrally recurved elongate conoid with bluntly pointed or narrowly rounded terminus. The new species is typologically similar to D. lini, sharing a large body, conspicuous bursal flap, long PUS, and spicule shape, but can be distinguished from it by the absence of variation in the female tail shape, i.e., the tail of the new species is always long and strongly ventrally curved, while the tail shape varies more in D. lini. A previous molecular phylogenetic analysis suggested that the new species is fairly close to D. lini, but can be distinguished from it by the 1.0% (16 bp) difference within 1.6 kb of the 18S and 3.7% (26 bps) difference within 0.7 kb of the D2-D3 LSU ribosomal RNA genes. The newly found nematode is described and illustrated herein as D. alienae n. sp.

Raffaelea quercivora (Japanese oak wilt).

Raffaelea quercivora, together with ambrosia beetle Platypus quercivorus as a vector, is the causal agent of Japanese oak wilt. P. quercivorus occurs from south to east Asia, including Japan, and is associated with trees in the Fagaceae family. R. quercivora is considered native to Japan, Taiwan, Indonesia, Thailand and Vietnam. In Japan, Quercus serrata and Q. crispula [Q. mongolica] are particularly susceptible to Japanese oak wilt, with high rates of mortality. Although there have been reports of the co-occurrence of R. quercivora and P. quercivorus outside of Japan, tree mortality caused by this species complex has never been recorded in these cases. R. quercivora is not on an alert list or listed as a regulated pest in any part of its native range. Although R. quercivora/P. quercivorus are not considered invasive, if they were introduced into susceptible oak forests, possibly via international transport of wood products, there is potential for them to cause extensive tree mortality in other geographic regions.

Raffaelea quercivora (Japanese oak wilt).

Raffaelea quercivora, together with ambrosia beetle Platypus quercivorus as a vector, is the causal agent of Japanese oak wilt. P. quercivorus occurs from south to east Asia, including Japan, and is associated with trees in the Fagaceae family. R. quercivora is considered native to Japan, Taiwan, Indonesia, Thailand and Vietnam. In Japan, Quercus serrata and Q. crispula [Q. mongolica] are particularly susceptible to Japanese oak wilt, with high rates of mortality. Although there have been reports of the co-occurrence of R. quercivora and P. quercivorus outside of Japan, tree mortality caused by this species complex has never been recorded in these cases. R. quercivora is not on an alert list or listed as a regulated pest in any part of its native range. Although R. quercivora/P. quercivorus are not considered invasive, if they were introduced into susceptible oak forests, possibly via international transport of wood products, there is potential for them to cause extensive tree mortality in other geographic regions.