This winter, an elderly gentleman I deal with in the community gardens called me from Arizona because he was worried about his remaining three pine trees. He meant to do something to protect them from the mountain pine beetle before he fled south in January, but forgot. I told him I would look into it to see what the best course of action is this year.

The Mountain Pine Beetle

I know it’s been a problem in our area for several years, and although some areas in Montana had limited flights of females last year, they still seem to be plenty active. As the name implies, mountain pine beetles prefer pines particularly lodge pole, Ponderosa and Scotch pines although they will go after other species if in a pinch.

These nasty beetles burrow into the inner bark of the tree, and the larvae feeds on it for nearly a year. Then they transform into a pupae, then adult and fly off to infest the next stand of trees. They’ve decimated 4 million acres in Montana, plus more throughout the West.

Once the mountain pine beetle burrows into the tree, it’s pretty much toast. On rare occasions, if a tree is healthy, sometimes it can fend off the attack by creating more resin to pitch out the beetles. The one positive outcome of the cold, wet spring we’ve had this year is it helps boost the health of the trees. Part of the reason the beetle infestation reached epic proportions these last few years is we’ve been slugging through a nearly decade long drought. Now that it appears the tides have turned, there’s hope that the beetle plague will soon end.

Spraying Trees for Mountain Pine Beetles

The time to fend them off is now. In May and June its wise to spray your trees with Sevin SL or XLR. For a somewhat less toxic concoction try Astro or Onyx, which are Permethrin compounds.

The most important aspect of spraying your trees is to spray everything that is more than five inches in diameter, including branches. I talked to our city forester this week, and he said hes seen several cases where homeowners sprayed their own trees, but couldnt reach far enough up the tree. The beetles still attacked their trees, and they lost them.

If you hire someone to do it make sure they’re using the approved ingredients. Using other products may not adhere well enough to the bark of the tree to make an impact. Also make sure they are properly licensed. In Montana you need to be a licensed applicator to apply the above sprays to someone elses trees.

Pheromone Pouches For Trees

The other option is to hang the pheromone pouches on the trees in July. These basically make the beetles think the tree is already infested, and they continue their search for a vulnerable host. Hang them around 10-feet high, which is the height beetles prefer, when theyre looking for their next victim.

These preventive measures do work. It can be expensive to properly treat everything, but its a heck of a lot cheaper to protect your trees than it is to replace them, especially if its one of those giants that will take a lifetime to grow to the same height.

Photo copyright of Sherwoodimagery via istock.