Study on Early Diagnosis for Pine Wilt Disease Causedby Bursaphelenchus xylophilusⅡ.The Effect of Pine Species, Dose and Nematode Origin on Oleores in Exudation Method Study on Early Diagnosis for Pine Wilt Disease Caused by Bursaphelenchus xylophilus Ⅰ.Early Diagnosis for Pine Wilt Disease by Bursaphelenchus xylophilus Parasiting in Pinus massoniana and P.thunbergii Early diagnosis of low-value forest: An approach of ecological factors Application of Oleoresin Exudation Method for Controlling Pine Wood Nematode Disease by Bursaphelenchus xylophilus in Changdao County of Shandong Province