Field guide to exotic pests and diseases: Pinewood nematode
Distribution: USA, Canada, Japan, China, Korea and Taiwan.
Hosts: pines, Douglas fir, spruce, larch, fir.
Signs: first visible sign may be arrested growth, and foliage of a fading green or slight yellowing colour; foliage of infected trees turns reddish brown; trees can die so quickly that brown needles cling to twigs.
Yellowing or wilting and browning begin soon after colour begins to fade. Resin production falls; branch cut from diseased tree may not produce any resin; branch twigs become brittle and dry and break easily. Various wood-inhabiting beetles can vector the nematode.
Likely pathway: nursery stock, bark, lumber and wood packaging material including dunnage and insects.
Potential impact: has caused very severe losses in pine forests of Japan and China with > 2 million cubic metres of wood lost per year in USA.