We determined the incidence of Bursaphelenchus species in declining Pinus sylvestris stands in the Swiss Alps. A total of 217 trees showing different degree of decline were sampled from various locations in Valais between 2001 and 2004. Bursaphelenchus species were only found in recently dead or dying trees with an overall incidence of 40%. There was a positive relationship between Bursaphelenchus infestation and blue stain in these trees. Five Bursaphelenchus species were identified: Bursaphelenchus vallesianus, Bursaphelenchus mucronatus, Bursaphelenchus sexdentati, Bursaphelenchus leoni and Bursaphelenchus silvestris. The most frequent species were B. vallesianus detected in 75% and B. mucronatus in 20% of all Bursaphelenchus-positive trees. Bursaphelenchus vallesianus is a recently described species within the B. sexdentati group, and could be a contributing factor in the observed pine decline in Valais.

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Correct identification of the pine wood nematode Bursaphelenchus xylophilus becomes more difficult, as more related or similar species are described. Spread of the nematode is being monitored worldwide, and in view of the fact that several new Bursaphelenchus species have been described, identification keys should be adjusted accordingly. Based on the identification key of the xylophilus group published by Braasch (2008) and the revised intrageneric grouping of Bursaphelenchus by Braasch et al. (2009), an improved dichotome morphological key including newly described species (B. paraluxuriosae, B. populi, B. macromucronatus, B. firmae, B. koreanus and B. gillanii) is presented. The recognition of the quarantine pest B. xylophilus using morphological characteristics in laboratories of the National Plant Protection Services is facilitated by a simplified key.

A new Bursaphelenchus species of the xylophilus group was detected in coniferous packaging wood imported with goods from China in 2011. The new species is described herein and compared with other species of the xylophilus group. Bursaphelenchus gillanii sp. n. has a slim body (a = 31 (28-34) and 33 (29-36) in females and males, respectively), c′ = 3.8 (3.2-4.5) and 2.1 (1.7-2.5) in females and males, respectively, a large vulval flap, a 5-7 μm long digitate mucro as a continuation of the female tail, excretory pore at or closely posterior to the median bulb, strongly arcuate spicules, 34 (31-37) μm long as measured along the median line, with prominent pointed rostrum and small cucullus. The ITS-RFLP pattern of the new species obtained by digestion of the PCR product with RsaI, HaeIII, MspI, HinfI and AluI is different from other known Bursaphelenchus species. Results of sequencing the ITS1/2 region demonstrate the close relationship of the new species to B. mucronatus and B. xylophilus.

Summary Bursaphelenchus leoni is redescribed, using morphology, morphometrics and molecular data, based on a population isolated from dead Pinus massoniana in Zhejiang Province, China. It is characterised by a lateral field with three lines, a 12-15 μm long stylet with small basal swellings, excretory pore located one body diam. posterior to nerve ring, spicules mitten-shaped, dorsally and ventrally arcuate, with lamina smoothly tapering towards broadly rounded distal tip without hook-like process in the Chinese population, condylus broadly rounded with a small dorsally bent hook, rostrum triangle or conical with finely rounded tip. The bursal flap is long, spade-like with posterior margin truncate or irregular. A 2-3 μm long vulval flap is present. The female tail is long and conical (c′ = 5.3-6.9), with the terminus finely rounded, or occasionally pointed. The Zhejiang population of B. leoni is close to B. eidmanni and B. silvestris, which all belong to the leoni-group sensu Braasch et al. (2009). Comparison with the description of B. borealis led to the conclusion that B. leoni and B. borealis are conspecific, the latter being regarded as a junior synonym of the former.