Occurrence Characteristics,Pathogen Identification,Mortality And Movement Behavior Of Bursaphelenchus Xylophilus Weihai Population

Occurrrece of pine wilt disease in Chengshan forestry, Weihai city, Shandong was investigated in2010. Spatial and temporal dynamic and distribution was monitored inside pine trees. Samples were sampled in Chengshan Weihai city, Changdao Yantai city and Lushan Zibo city respectively, and nematodes were extracted using the method of Baermann. Specimen of male and female were mounted in permanent slides, photographed and morphometrics was mesured using the light microscope. Morphological observation of female and male were described in this paper. In order to effective nematicidal chemicals of B. xylophilus was selected by the bioassay method. The toxicity of copper sulfate, emamectin benzoate and matrine against pine wilt nematode (PWN) were evaluated by mortality and movement behavior of Bursaphelenchus xylophilus; Meanwhile, the effect of different dosages of common solvent (methanol, absolute ethylalcohol, acetonum and DMSO) on movement behavior of Bursaphelenchus xylophilus were observed, thus providing an important biology information to research primary drug preparation and plant extract solvent use. The results were showed as following:1. Dynamics change of B. xylophilus in Chengshan forestry, Weihai city, ShandongFrom March to October in2010, dynamics change of B. xylophilus was investigated in Chenghill forestry, Weihai, Shandong. The results showed that occurrence of pine wilt disease was serious from July to October; nematode population in the treetop was higer than that of the trunk base, and nematode population in middle and lower tree was the least; the number of nematode at0-1.2m and4.0-4.8m distance above the ground were significantly higher than that of others parts, there was no significant difference among other sections; Nematode populations in different orientation of tree at distance above the ground were different.2. Morphometrics and molecular identification of B. xylophilus from Weihai, Yantai, Zibo, ShandongMorphometrics and molecular identification of female, male adult are described in this paper. Three nematode populations have common characteristic:femanle and male vermiculate, the body slender; lip region high, shrinkage significantly; the style was shorter than type species, with small basal knobs; hemizonid conspicuous, about twothirds body width behind medium bulb; the female vulva clearly shows the distinct and long overlapping vulva flap, with the vulva at an apporoximately90°angle with the surface; the male spicules large,uniquely arcuate, paired, with sharply pointed prominent rostrum; distal ends of spicules with typical disc-like expansions. The3nematode groups different characteristic:Weihai and Yantai populations female tail subcylindrical, usually with broadly rounded terminus, without caudal muero; the male tail arcuate, terminus pointed, the ventrad bending, Weihai population witout copulatory bursa, Yantai a few population have bursa, mostly copulatory bursa degradation. Zibo nematode population female tail with a digitate terminus and a caudal mucro of about1μm (<2μm), the male tail was surrounded by terminal bursa. The molecular characteristics of nematode’s DNA were measured with specific amplification and rDNA-ITS-RFLP. The results showed that the population in Chengshan Weihai city, changdao Yantai city and Lushan Zibo city were identified as Bursaphelenchus xylophilus (Steiner&Buhrer,1934) Nickle,1970.3. The movement behavior effect of Bursaphelenchus xylophilus by different chemicals and solvents treatmentThe VAA value decreased with increased duration of exposure by different chemicals treatment in this experiment. Although some juveniles remained live, minimal mortality with only head or tail slowly twitch every several seconds was observed, other nemtodes lost their activity when copper sulfate at a concentration of100mg/18hours and emamectin benzoate at a concentration of2mg/12hours. The nematode VAA value decreased after8hours exposure to matrine at a concentration of1000mg/1. Although juveniles remained live after8hours, but90%body shrinkage,only1/2head or tail move right and left, move slowly. The VAA value had not significantly change after different time exposure to1%methanol,1%absolute ethylalcohol,1%DMSO, and acetonum; when a concentration of3%, the activity of the nematode changed significantly (P<0.05) with different concentrations compared with the distilled water control; the VAA value decreased with increased duration at a concernation of5%and10%, the movement behavior of nematode change significantly (P<0.01).4. The effect of different dosages of chemicals on mortality of Bursaphelenchus xylophilus in vitroOf the3pesticides tested in this experiment, copper sulfate and emamectin benzoate showed stronger activity against the nematode Bursaphelenchus xylophilus at low concentration. The mortality was100%after24hours of exposure to copper sulfate at a concentration of100mg/1. The median lethal concentration (LC50) of copper sulfate against B. xylophilus at8,24,48, and72hours was31.634,7.353,6.557and5.568mg/1, respectively. The mortality was94.47%after2hours of exposure to emamectin benzoate at a concentration of2mg/1. The median lethal concentration (LC50) of emamectin benzoate against B. xylophilus at5,24,48, and72hours was0.8407,0.2068,0.0369and0.0354mg/1, respectively.