Factors in Pinus species affecting the mobility of the pine wood nematode, Bursaphelenchus xylophilus.

The chemical nature of the substance responsible for straightening and immobilization of the pine wood nematode, Bursaphelenchus xylophilus, has been studied. The active substance was contained in the first- and second-year twigs of both the pine wilt resistant species, Pinus taeda, and the susceptible species, Pinus densiflora. The quantity of the active substance from P. taeda was greater than that from P. densiflora. The substance was a water soluble, highly polar material whose molecular weight was in the range of 1, 500 to 6000. The active substance consisted primarily of carbohydrates and possibly a very low concentration of phenolics lost its biological activity upon methylation. The substance was hydrolyzed only under rigorous acid hydrolysis conditions and thus lost its biological activity. Bursaphelenchus xylophilus did not have a general immobilization sensitivity to either phenolics or carbohydrates as a class.