Historically, the western pine beetle has been a disorderly-but-manageable guest within the outer armor of healthy ponderosa pine trees. But some relationships go from bad to worse, slowly or all at once.
“When I work with forest owners, I explain that tree competition, weather, climate, disease, and, for eastern Washington especially, availability of water all influence the health of the ponderosa pine,” said Washington State University Extension Forester Andy Perleberg. “Once a tree is stressed from damage or water deficiency, pine beetles can gain a foothold and finish them off.”
The pine beetle is small. Most are about the size of a grain of rice. Female beetles drill through the tough outer bark, then carve a route toward the tree’s phloem, a nutrient-rich layer of cells. The extended gallery of beetle-hewn paths look like worm trails in soil and provide the perfect environment for pine beetles to reproduce.
Yet the ponderosa pine is not without defenses, which come in the form of resin ducts that litter the phloem. The unfortunate beetle that drills into a resin duct triggers an avalanche of pitch that cements it in perpetual stasis.
“If you see globs of pitch on the outside of a tree that are yellow or cream colored, that means the tree won,” said Perleberg.
Coppery-brown sawdust-like shavings outside of a beetle-made hole can tell a different story.
“There could be many reasons a tree couldn’t produce enough defense resin,” said Perleberg. “I typically look for tree crowding, sources of root damage, and whether we’re in a drought year, drought decade, or multiple drought decades, like we are now.”
Pine beetle populations hit a 16-year high in 2022, with more than 40,000 acres of Washington state ponderosa pine forests fatally impacted by their attacks, according to the Washington State Department of Natural Resources. Drought conditions and heat events may be driving the increased beetle activity and wave of tree mortality. The dead timber can serve as potential tinder for wildfire.
Despite the negative consequences of pine beetle activity, Perleberg is quick to point out that the native beetle has always served an important ecological role within the forests of Washington, historically killing only the weakest pines. Those pines that can grow large enough tend to survive.
“I educate forest landowners on the relationship between tree diameter and insect and disease resistance,” Perleberg said. “Trees portion out their energy, first to root growth, then into upward growth to increase their height, then into diameter growth to support a big root system and a heavier top. It’s when we start to see increases in diameter that the tree is most resistant to pests and diseases.”
The pine beetle is just one of the featured topics at Perleberg’s upcoming Forest Owners Winter School on Feb. 24 at Spokane, Wash.
Since 2009, more than 7,000 individuals and families have taken part in the event, leaving with important knowledge on forest management practices.
“Forests cover about 50% of Washington state’s land,” Perleberg said. “Of that, 20% of forests are family owned, which is roughly 5.8 million acres. That’s a huge area to manage, so by providing forest owners with management knowledge, we are decreasing wildfire risk while protecting vital watersheds, timber resources, and wildlife habitats.”
Forest Owners Winter School includes nearly 20 courses on topics ranging from tax benefits and landowner financial assistance to managing root diseases and wildfire risks.
“It’s not possible to take all the courses we offer at this one-day event, so we tend to get repeating participants from year to year,” Perleberg said. “People are interested in understanding how they can create a healthy, safe, and productive forest.”
Further information
Timely education on forest management best practices drew more than 6,000 forest landowners to WSU Extension Forestry programs in 2023 alone. More than 5,000 participants implemented new management practices, saving an estimated $100 million for private landowners and the state of Washington. Visit the WSU Extension Forestry website to learn more about their impactful programming.
Media contact
Andy Perleberg, phone: 509-630-4217, email: andyp@wsu.edu