As Willamette Valley ponderosa pine stands age, periodic thinning is required to maintain the growth and vigor of the stand. Slash produced by management activities provides the ideal breeding habitat for the California fivespined ips (Ips Paraconfusus). If populations of this bark beetle buildup in slash, the emerging beetles can attack and kill standing green pine a mile or more from the slash piles. By the time the crowns of trees turn orange, it is too late for control measures since the typical outbreak only lasts one year. How serious is the problem? In 2003 an industrial landowner suffered significant damage to a Valley pine plantation as a result of not managing slash at a nearby logging operation. In California, where this beetle is also a problem, there are actually laws requiring slash abatement for Ips under certain conditions.
Ips outbreaks tend to be more damaging during periods of drought, but are not dependent on drought and can occur as long as breeding material, thinning slash or storm damaged trees, are available.
The only proven approach to preventing Ips damage is to avoid accumulations of fresh slash at certain times of the year and dispose of storm damaged trees as soon as possible. Here are some management recommendations that can prevent Ips outbreaks and minimize problems.
- Avoid creating fresh pine slash, including large branches and tree tops, with a diameter >3” between January and the end of July.
- Storm damaged pine >3” in diameter, including branches, should be salvaged, chipped or cut to small pieces and scattered in openings so it dries rapidly.
- If creation of green slash is unavoidable in the January-July period, any pieces >3” in diameter should be chipped, or cut into small pieces and scattered in openings. Do not pile slash since this slows the drying process.
- Keep all fresh pine slash, logs, or firewood several yards away from living pines.
Fresh pine slash created in the safe period, August – December, may attract a few Ips, but the resulting population buildup is minimal and does not result in attacks on standing trees.