Bursaphelenchus xylophilus

Bursaphelenchus xylophilus showed greater rates of growth than B. mucronatus in single and mixed treatments. The invasive species was competitively superior to the indigenous species in mixed treatments (fungi and pines). This competitive advantage in pines, prior to the beetles’ infestation, could explain the greater abundance of the invasive (68%) species over the indigenous in the insect vector M. galloprovincialis.

Bursaphelenchus xylophilus showed greater rates of growth than B. mucronatus in single and mixed treatments. The invasive species was competitively superior to the indigenous species in mixed treatments (fungi and pines). This competitive advantage in pines, prior to the beetles’ infestation, could explain the greater abundance of the invasive (68%) species over the indigenous in the insect vector M. galloprovincialis. (Altemayer et al. 2008)

The process of inter-specific hybridization between the invasive, highly pathogenic pinewood nematode, Bursaphelenchus xylophilus and the Eurasian-native, relatively harmless B. mucronatus has been examined. The research showed that hybridization between both species was possible in F1 and to some extent in subsequent offspring generations. In the general body plan, the hybrids resembled the wild-type parental species but differed in various morphological/anatomical details. The changes ranged from seemingly indistinct to heavily distorted or occasional missing of particular structures. The most affected were spicules, female tails, the development of gonads and the position of the excretory pore. The hybridization led to various distortions of mating, gametogenesis, embryogenesis and juvenile viability, and development in F1, F2 and subsequent generation offspring, which severely affected the nematode reproductive potential. (Tomalak & Filipiak, 2021)

The decisive factor in developing epidemic infestation in Japan was the contact between sawyers and nematodes. The JPS is native to Japan but was a rather scarce insect until it came into contact with the PWN. The spread of disease is facilitated by an obligatory mutualism between PWN and JPS: the JPS helps the PWN be transmitted to a new host tree, while the PWN supplies the JPS with newly killed trees on which to lay eggs (Fig. 1). The JPS adults emerge in early summer and feed on young twigs for maturation, meanwhile PWN dauerlarvae invade healthy pine trees. (Kiritani & Morimoto, 2004)