Number Of Pine Wood Nematodes Research Articles

Population dynamics of pinewood nematode and the endoparasitic fungus Esteya vermicola: interactions under experimental conditions

Esteya vermicola (Ophiostomataceae), an endoparasitic fungus, exhibits great potential as a biological control agent against pinewood nematodes (PWNs). The present study reports the interaction between PWNs and E. vermicola at different spore concentrations, number of PWNs and the time of culture. The addition of PWNs enhanced the sporulation of E. vermicola after 10 days of culture. The 5-day-old cultures of E. vermicola prior to addition of PWNs increased the highest amount of sporulation than that of 10- or 15-day-old cultures. The PWNs were completely killed by E. vermicola in the pine tree powder culture medium at the concentrations of 107 and 108 colony-forming-units (CFU) per ml. The interaction of the PWNs and E. vermicola was that PWNs provide nutrition to E. vermicola, however, the PWNs can also feed on mycelium of E. vermicola. The effect of E. vermicola on control of PWNs was determined by the population size, time of pest infection and the duration of co-infection.

The developmental process of xylem embolisms in pine wilt disease monitored by multipoint imaging using compact magnetic resonance imaging.

In pine wilt disease (PWD), embolized tracheids arise after virulent pine wood nematodes (PWN), Bursaphelenchus xylophilus, invade the resin canal of pine tree; infected pine trees finally die from significant loss of xylem water conduction. We used a compact magnetic resonance imaging system with a U-shaped radio frequency (rf) probe coil to reveal the developmental process of the xylem dysfunction in PWD. Multiple cross-sectional slices along the stem axis were acquired to periodically monitor the total water distribution in each 1-year-old main stem of two 3-year-old Japanese black pines (Pinus thunbergii) after inoculation of PWN. During the development of PWD, a mass of embolized tracheids around the inoculation site rapidly enlarged in all directions. This phenomenon occurred before the significant decrease of water potential. Some patch-like embolisms were observed at all monitoring positions during the experimental period. Patchy embolisms in a cross-section did not expand, but the number of patches increased as time passed. When the significant decrease of water potential occurred, the xylem dysfunctional rate near the inoculation point exceeded 70%. Finally, almost the whole area of xylem was abruptly embolized in all cross-sections along the stem. This phenomenon occurred just after water conduction was mostly blocked in one of the cross-sections. Thus, it appears that the simultaneous expansion of embolized conduit clusters may be required to induce a large-scale embolism across the functional xylem. Consequently, xylem dysfunction in infected trees may be closely related to both the distribution and the number of PWN in the pine stem.

Abundance-dependent transmission of the pinewood nematode, Bursaphelenchus xylophilus (Nematoda: Aphelenchoididae), to the Japanese pine sawyer, Monochamus alternatus (Coleoptera: Cerambycidae), adult in its pupal chamber

The transmission ratio of the pinewood nematode (PWN), Bursaphelenchus xylophilus, to the emerging adult Japanese pine sawyer (JPS), Monochamus alternatus, in its pupal chamber is a determinant of the number of the nematodes carried by JPS beetles. To investigate the factors affecting the transmission ratio, we counted the number of the nematodes carried by 36 newly emerged JPS beetles and the number remaining in and around their pupal chambers, and then estimated the transmission ratio (the number of nematodes carried by a JPS adult as a percentage of the total number of nematodes aggregating in and around its pupal chamber). The total number of nematodes aggregating in and around a pupal chamber ranged from 0 to 19,041, and the number of nematodes carried by a beetle ranged from 0 to 18,920. The transmission ratio correlated with neither the water content of the wood around the pupal chamber nor the degree of wood discoloration caused by blue-stain fungus. The transmission ratio varied with the abundance of the nematodes aggregating in and around the pupal chamber. In pupal chambers with more than 1,000 nematodes, almost all the nematodes were transmitted to the beetle. However, in pupal chambers with fewer than 1,000 nematodes, the transmission ratio varied greatly, from 0 to 100%. These results suggest that aggregation of many PWNs in the pupal chamber might stimulate transmission of the PWNs to the JPS adult and that this abundance-related transmission might contribute to the large variation in the number of PWNs carried by the JPS beetle.

Effect of fungus inoculation on the number of Bursaphelenchus xylophilus (Nematoda: Aphelenchoididae) carried by Monochamus alternatus (Coleoptera: Cerambycidae)

Abstract To confirm the effects of wood-inhabiting fungi on the number of pine wood nematodes (Bursaphelenchus xylophilus) carried by the Japanese pine sawyer (Monochamus alternatus), we attempted to change the mycoflora and also to prevent blue-stain fungi, the main food source fungi of the nematodes, from spreading throughout pine wilt-killed Pinus densiflora wood by inoculating 12 other fungi into the dead logs. Trichoderma sp. 2, Trichoderma sp. 3, and Verticillium sp. inoculation treatments tended to decrease the number of the nematodes carried by the beetles. These fungi were more or less antagonistic to the blue-stain fungus Ophiostoma minus, and Trichoderma sp. 2 and Trichoderma sp. 3 grew faster than O. minus on four kinds of media.

Variation in the number of Bursaphelenchus xylophilus in aliquots of stock suspensions artificially inoculated on to subject pines

AbstractThe procedures used to estimate the number of pine wood nematodes (Bursaphelenchus xylophilus) in stock suspensions and the variation in the number of nematodes in inocula applied to subject pine trees were examined. The findings suggest that preparing dilutions using 1 ml aliquots and making two replicate dilutions and three replicate counts of each dilution (or three dilutions and two counts) results in a precision of ±15% and an elapsed time for the majority of the population estimate procedures of less than 900 seconds. Under these conditions, the variation in the number of nematodes in the inocula was estimated to range from 55 to 156% of the intended population. This variation in the number of pine wood nematodes inoculated is unavoidable; thus, researchers should account for this variation when interpreting data from trials involving the artificial inoculation of pines.