Fighting the Pine Beetle
By Carol Rawle

It's heart breaking to drive down the ranch roads each fall and see how many beautiful ponderosa pines have been killed by mountain pine beetle.  It's even more heart breaking if beetle killed trees happen to be located around your construction site.  The very location of your new home may have been determined with many of these beautiful trees in mind.  To lose them is no small matter.  Removing large dead pines near your house is a delicate operation if you don't want them to fall on your new home during the felling process, but to leave them isn't an option either, since dead trees eventually fall over.

We aren't completely at the mercy of these insects, however.  Until recently, it's been a hazardous, and sometimes expensive, proposition treating infested timber.  But now, thanks to a recent study published by the U.S.  Department of Agriculture, there's a relatively simple and inexpensive way to treat infested trees that have been cut down so that the beetle will not live and reproduce to infest the healthy trees nearby.

Mountain pine beetle (DENDROCTONUS PONDEROSAE) has a one year life cycle.  The insects are most active during the warm months, and are attracted to the pitch generated by clearing trees for a construction site.  They enter green trees and produce their young.  This causes the infested tree to show signs of "pitching out" the invaders.  Around the invasion site, look for "popcorn" resinous lesions, brownish tan in color.  However, a lot of trees don't show any signs of infestation until it's too late to save the tree.  When the needles turn brown, you have a dead tree on your hands.  AND you also have a whole community of new beetles.  (Click Here to read an earlier article on how to treat a live tree for pine beetle.)

The best way to deal with this new generation of beetles is to cut down the infested tree.  In the past, you would have to purchase expensive, and often very toxic, insecticides to treat the cut up wood.  The wood can be burned immediately, but if left lying around, the larvae will mature and move out to infect new trees.  The problems with using insecticides are many, including toxic effect on humans and animals.  Also, some of the most effective insecticides are no longer available due to this high toxicity, and the remaining insecticides aren't nearly as effective, and most often require a special license to purchase.

Now there is a safe and relatively cheap method of killing mountain pine beetle in downed trees.  Anyone can purchase it, costs around $1.25 per gallon, and is safe for humans, animals and the environment when handled and applied correctly.  It's common variety, everyday diesel fuel, the kind you get at the gas station and burn in diesel engines.

You will need to handle the diesel fuel carefully because it can be harmful to humans, animals, and plants.  You need rubber gloves (chemical resistant ones that you can purchase at Big R) and a watering can or pump sprayer, and several gallons of diesel fuel, about 3 gallons per tree.  Solar radiation is an important element in this treatment so you need to arrange the infested cut logs with their ends pointing north and south, so that the logs receive maximum sun exposure.  Choose a spot that gets all day sun.  Apply the diesel with the sprinkling can to the infested log, letting the fuel slowly seep in, taking care not to let it run off onto the ground or splash adjacent vegetation.  When the oil begins to drip down the sides of the log, turn the log, applying more diesel until all the log surface is good and saturated.  As long as you don't let the diesel puddle onto the ground, there is no environmental hazard.  You may stack the treated logs two deep.  The beetles should be dead in four to six weeks, and you should have a 90 percent to 100 percent kill.  The diesel breaks down in that time, and the wood should be perfectly safe to burn in your wood stove or fireplace at any later date.

If you are clearing your building site, even in the winter, and anticipate that the downed wood will be lying around for awhile, you must treat it since it can attrack pine beetles.  The remaining tree stump should also be treated.  This is very important if you want to protect the ponderosas remaining around your home site.  Mountain pine beetle can also attack pinons, so the same precautions should be taken.

To do nothing is a huge gamble.  The mountain pine beetle is becoming more entrenched on the ranch each year as more and more property owners move here and build.  By cutting down and treating your infested trees and by treating cut wood removed from around your building site, you are helping to ensure that the trees that you really value will remain healthy for years to come.  And you will be doing your part for the bigger picture, helping to prevent a large scale loss of trees on our ranch to this very damaging insect.


For a copy of the study, contact the Rocky Mountain Research Station, 240 West Prospect Road, Fort Collins, CO 80526.  Ask for Researh Note RMRS-RN-13 Diesel Fuel Oil for Increasing Mountain Pine Beetle Mortality in Felled Logs September, 2002.