Analysis of Influencing Factors of Pine Wood Nematode Disease in Lu an City Based on GIS

[Objectives]The paper was to figure out the distribution of Monochamus alternatus in the stumps of pine wood nematode infected wood in Lu'an City and to provide a theoretical and practical basis for differentiated prevention and control of pine wood nematode disease in the future.[Methods]The factors influencing the number of epidemic small classes and infected plants in all counties and districts of Lu'an City were analyzed by GIS method,and the number of worms and wormholes of M.alternatus inside and outside the stumps of pine wood nematode infected wood in Lu'an City were investigated on the spot.[Results]There were 98,40,54,781,193,268 and 34 epidemic small classes of pine wood nematode disease,and 7241,6099,9532,39161,11079,49876 and 4853 infected plants in Yu'an District,Jin'an District,Yeji District,Shucheng County,Huoshan County,Jinzhai County and Huoqiu County,respectively.Pine wood nematode disease in Lu'an City mostly occurred in Huoshan County,Shucheng County and Jinzhai County,with relatively high altitude,paddy soil,the annual precipitation higher than 2062 mm,and the annual average temperature lower than 16.2℃.The number of diseased plants of pine wood nematode disease was positively correlated with altitude and annual precipitation,and was negatively correlated with annual average temperature.The number of worms and wormholes in pine wood nematode infected wood was very small at different altitudes,stump heights and stump diameters.[Conclusions]The pine wood nematode infected wood can be differentially processed after stump treatment,and stumps can be peeled.The results will provide a theoretical and practical basis for differentiated prevention and control of pine wood nematode disease in the future.

Investigation of beetle species that carry the pine wood nematode,Bursaphelenchus xylophilus(Steiner and Buhrer)Nickle,in China

In order to found new carriers of pine wood nematode(PWN),Bursaphelenchus xylophilus,beetles were collected from pine wilt disease-affected areas in six provinces in China.A total of 8830 beetles of 29 species was collected and examined to determine whether they were PWN carriers.Eight species were identified as carriers.Results included the first worldwide report of Monochamus uigromaculatus,Semanotus siuoauster,and Uraecha angusta being carriers of PWN,and the first report from China of A rhopalus rusticus carrying PWN.Monochamus alternatus was commonly collected in all six provinces and was the dominant species in four inland affected areas and A.rusticus was dominant in two coastal affected areas.The species varied between different neighboring regions in the same province.The distribution of the same species varied considerably over different regions.

Emamectin benzoate 9.7%SL as a new formulation for a trunkinjections against pine wood nematode,Bursaphelenchus xylophilus

In this study,we investigated the preventive effects of emamectin benzoate 9.7%SL,which was newly developed to reduce the injection volume and number of injection holes required to protect against pine wood nematode.None of the Pinus thunbergii trees injected with emamectin benzoate 9.7%SL at 0.3 mL/cm diameter at breast height(DBH)died within 2 years of inoculation with pine wood nematodes.Emamectin benzoate 9.7%SL injected at 0.6 mL/cm DBH resulted in no tree mortality for 3 years.Mean residue of emamectin benzoate 9.7%SL in pine twigs injected with 0.3 mL/cm DBH was 0.490μg/g at 1 year after injection and 0.303μg/g after 2 years.These residues values are greater than 0.031μg/g,previously determined IC95 value for emamectin benzoate against the pine wood nematode.Our field experiment and residue analysis showed that emamectin benzoate 9.7%SL could be a substitute agent for emamectin benzoate 2.15%EC,which is widely used to prevent pine wood nematode in the field and that injection volume and number of injection holes can be greatly educed using this new formulation,which will reduce injury to the cambium,interruption of water movement,and infection of inoculation wounds by wood-decay or blue stain fungi.

Adaptation of pine wood nematode,Bursaphelenchus xylophilus,early in its interaction with two Pinus species that differ in resistance

Pine wilt disease(PWD)is one of the most devastating diseases of Pinu s spp.and is caused by the pine wood nematode(PWN),Bursaphelenchus xylophilus(Steiner&Buhrer)Nickle.To study adaptation of PWN to survive in hosts that differ in resistance,we examined the self-regulatory characteristics of PWN at the biological and molecular levels early in the interaction.Two-year-old susceptible Pinus thunbergii and resistant Pinus taeda were selected for this experiment,and changes in PWNs after inoculation were assessed.q RT-PCR was used to detect changes in genes related to PWN pathogenicity and detoxification.The results showed that the migration and reproductive abilities of PWNs in P.thunbergii were stronger than those of PWNs in P.taeda.After 7 d,the number of nematodes in P.thunbergii was approximately 3.2-fold higher than in P.taeda.After 15 d,the number of nematodes in P.thunbergii was approximately twofold higher than that in P.taeda.Because PWN can adjust its sex ratio after infection,we compared the sex ratio of uninoculated PWNs,to that in the two pine species.In P.thunbergii,the female to male ratio first decreased and then stabilized over time;in P.taeda first decreased and then increased.Relative fat accumulation in PWNs increased significantly after the PWNs entered the tree body;the accumulation rate in P.thunbergii was higher than in P.taeda at 7 d,but lower after 15 d.Scanning electron microscopy(SEM)showed significantly more bacteria on the surface of PWNs in P.taeda compared with PWNs in susceptible P.thunbergii.At 12 h after inoculation,the expression of genes related to cell-wall degradation(Bx Beta1-4 and Bxpel1),effectors(Bx CDP1,Bx Sap B1),and active oxygen metabolism(Bxy-ctl-1 and Bx GST3)was 2–6×higher in the resistant pine than in the susceptible one.In contrast,in PWNs,the expression of autophagy-related genes Bx ATG1 and Bx ATG16 was 1.5–2 times higher in P.thunbergii than in P.taeda.These results indicate that the interaction between PWNs and pine trees with different resistance levels elicits a series of physiological and molecular adaptations that affect nematode reproduction and virulence.This study will help elucidate the adaptive mechanisms of PWN in different pine trees.

Resistance genes mediate differential resistance to pine defensive substances α-Pinene and H_(2)O_(2) in Bursaphelenchus xylophilus with different levels of virulence

The pine wood nematode(PWN),Bursaphelenchus xylophilus(Steiner & Buhrer) Nickle,is the pathogen of pine wilt disease(PWD) which can devastate forests.PWN can be of hi gh or low severity and the mechanisms underlying the differences in virulence are unclear.Therefore,it is necessary to study the relationship between differentiation of PWN severity and its resistance to the main defensive substances of pine species(i.e.,α-pinene and H_(2)O_(2)).The feeding rate and fecundity of PWN was examined at different levels of virulence under conditions of a-pinene and H_(2)O_(2) stress.Moreover,the expression patterns of the main resistance genes of PWN with different virulence were determined under conditions of α-pinene and H_(2)O_(2) stress.The feeding rate and fecundity of the high virulence strain AMA3 were higher than those of the low virulence strain YW4.The expression levels of the autophagy gene BxATG5,cytochrome P450 gene BxCYP33 D3,and glutathione S-transferase genes BxGST1 and BxGST3 in AMA3 increased significantly upon exposure to α-pinene for 2 h,while these genes showed smaller degrees of upregulation in YW4.Under conditions of H_(2)O_(2) stress,the expression levels of BxATG5,catalase genes Bxy-ctl-1 and Bxy-ctl-2,and the 2-cysteine peroxiredoxin gene BxPrx in AMA3 were higher than those in YW4.These findings suggest that high virulence PWN has greater resistance to pine defensive substances α-pinene and H_(2)O_(2) than low virulence PWN,and resistance genes mediate the differential resistance of PWN strains.This study will contribute to the clarification of the mechanism underlying virulence differentiation of PWN and will advance understanding of the pathogenic mechanism of PWD.

Mating and reproductive characteristics of the pathogenic nematode Bursaphelenchus xylophilus

Pine wood nematode(B ursaphelenchus xylophilus),one of the most destructive invasive species,has caused extremely serious economic,ecological and social losses in many countries throughout the world.Since the high reproductive rate of B.xylophilus PWN is the main cause of rapid death of its pine hosts(Pinus spp.),understanding the reproductive and population biology and the ecology of this nmatode are of great importance.This study mainly focused on analyzing the mating process and population structure under different combinations of sex ratios for mating.Reproductive efficiency of B.xylophilus peaked when the sex ratio(female to male)was 3.4:1.Phases of the mating process for the different sex-ratio combinations indicated that B.xylophilus had evolved alternative reproductive strategies to cope with complex copulating conditions to obtain a suitable population structure for further propagation.This research provides fundamental information on the mechanism that is responsible for the rapid population growth of B.xylophilus.

Control of Bursaphelenchus xylophilus in the State-owned Sishibacao Forest Farm of Yunyang County,China

In view of the fact that pine wood nematode disease is the most dominant disease in Pinus massoniana forests,which has the characteristics of strong infectivity,fast transmission speed,and great difficulty in prevention and control,a brief description was made to the occurrence status of pine wood nematode disease and difficulties faced with its control in the State-owned Sishibacao Forest Farm of Yunyang County,China,followed by the analysis on the prevention and control measures from aspects of strict control,epidemic situation monitoring,joint prevention and control,and clearance of infected trees,as well as the existing problems of pine wood nematode disease.Finally,reasonable suggestions including strengthening the construction of talent team were put forward,aiming to provide a beneficial reference for the scientific,efficient,and reasonable control of pine wood nematode disease in Pinus massoniana Lamb.forests of Yunyang State-owned Sishibacao Forest Farm.