Scotch Pine or as some people call them Scots Pine (Pinus sylvestris) is a common tree found on our property here at Des Moines Golf and Country Club. Over the years you may have noticed that we are slowly losing these beautiful trees. This is caused by a disease called "Pine Wilt"
Pine wilt is a disease of any pine tree caused by the pinewood nematode, Bursaphelenchus xylophilus. The pinewood nematode is native to North America and is not considered a primary pathogen of native pines, but is the cause of pine wilt in some non-native pines.
The pinewood nematode is transmitted (vectored) to conifers by pine sawyer beetles (Monochamus spp.) either when the sawyer beetles feed on the bark and phloem of twigs of susceptible live trees (primary transmission) or when the female beetles lay eggs (oviposition) in freshly cut timber or dying trees (secondary transmission). Nematodes introduced during primary transmission can reproduce rapidly in the sapwood and a susceptible host can wilt and die within weeks of being infested if conditions are favorable to disease development.
Basically what happens is the nematode multiplies so fast in the new host, that it plugs up the tissues that transport water and nutrients up and down the tree. This is called the vascular system. Once this system is plugged up, the tree starts to die and eventually has to be removed.
Here is a tree at DMGCC showing the signs of pine wilt.
Once we see a tree that has progressed this far, we remove it. Here is a photo of the trunk of the tree. You can see a blue stain in the wood. This is the proliferation of the nematode and you can see how it has multiplied and plugged up the conductivity tissue on the outside of the sapwood. Only thing that can be done is to cut it down and burn the wood immediately to help neutralize the moving of this pest.