The pinewood nematode (PWN), Bursaphelenchus xylophilus, the most important invasive species in pine forests of Asia, is transported to new pine hosts by beetles of the genus Monochamus. Third-stage dispersal juveniles (J(III)) aggregate in pupal chambers around the vector as it matures. We demonstrated that the ratio of three terpenes (alpha-pinene, beta-pinene, and longifolene at 1:2.7:1.1) released by larval Monochamus alternatus strongly attract J(III), whereas the different ratio (1:0.1:0.01) of these three terpenes found in healthy xylem of Pinus massoniana attracts only the propagative stage (J(n)) of the nematode. We suggest that the volatiles produced by the host plants could be the basis of a chemoecological relationship between plant parasitic nematodes and their vector insects. Capture of J(III) with terpene-baited trap tubes deployed for 2 hr in the field was demonstrated. This technique may lead to the development of rapid sampling methodologies for use at either ports-of-entry or in the field.
The third-stage dispersal juvenile (JIII) is the stage for survival and dispersal in the winter of the pine wood nematode, Bursaphelenchus xylophilus. Through investigations at different temperatures, we found two kinds of growth-arrested development, including the adult longevity extension and JIII formation induced by low temperature. They showed similar characters: densely packed lipid droplets and extended longevity. We considered that there were four stages in the formation of growth-arrested stages: induction, growth-arrested pathway, growth-arrested development and cold-tolerance duration. Moreover, at 4 • C there were significant changes in secondary metabolites, which may be related to signal communication and metabolism associated with the formation of growth-arrested stages. The results suggested that low temperature was necessary for the dispersal of pine wood nematode and influenced distribution and intensity of pine wilt.
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