By Amy Grotta, OSU Forestry & Natural Resources Extension – Columbia, Washington, & Yamhill Counties

Last week I attended Forest Health: State of the State, a biannual conference put on by OSU College of Forestry. A packed agenda covered insects, diseases, fire, drought, invasive species, climate change, and other topics. I always look forward to this meeting as an opportunity to brush up on my knowledge of these issues. The speakers came from various backgrounds, representing the many forest ecosystems and ownership types we have across the state, and the audience was equally diverse. With that in mind, I’ve tried to distill the takeaways from the conference that seem most relevant to small woodland ownerships in northwest Oregon.

ODF conducts an annual insect and disease aerial survey. Click on the image to be taken to a short video from the air.

What is forest health, anyways?  Our own Extension Specialist Dave Shaw kicked things off by reminding us that forest health is subjective, and based on our experiences, instincts, and goals. It’s easy to agree on whether an individual tree is healthy, but forest health is less concrete.

Resilience:  A common theme across many speakers was that of resilience: that a healthy forest is one that is capable of recovering after a stressful episode, such as a drought, fire, or insect outbreak, and is still able to provide the benefits that the owner and society desire.  A.J. Kroll, a wildlife biologist from Weyerhaeuser, suggested that resilience includes maintaining the productive capacity of a site. Using coarse woody debris (CWD) to illustrate his point, he suggested that a resilient forest has the ability to produce large trees that will eventually become CWD. While he didn’t elaborate, I interpreted that to include maintaining soil quality and productivity. Austin Himes, another speaker with industry background, added that forests also must be resilient to market changes or societal pressures.

“There’s a universe of small things that rely on coarse woody debris” said A.J. Kroll. CWD retained after a clearcut will later provide shelter for long-toed salamanders, once the forest regrows. Left photo: Amy Grotta; Right photo: Kathy Munsel, Oregon Dept of Fish & Wildlife
A bumble bee on a salal flower. Photo: Jim Rivers,

Pollinators:  Maintaining populations of pollinating insects is a key to the resilience of our society: without pollinators, we wouldn’t have many of the foods that we eat every day. Jim Rivers from OSU summarized some of the new and ongoing research about the value of westside forests to native pollinators. Most of our native bees nest in the ground, and of course they need flowering plants. Therefore, the short window of approximately four years post-harvest can be very valuable for pollinators.  This is when flowering plants thrive in full sun, and there are more areas of exposed ground for nesting sites.

Beyond these big-picture concepts, there was plenty to hear about “bugs, crud, and critters” – the things that often come to mind as forest (or tree) health issues.

Insects:  Forests on the westside have far fewer insect problems than east of the Cascades. Christine Buhl from the Oregon Department of Forestry emphasized that the best management of insect pests is preventative, by maintaining vigorous trees. This includes managing the Douglas-fir beetle, our primary westside insect pest, which likes stressed trees. But, Michelle Agne, another PhD researcher pointed out that climate change may create conditions that increase Douglas-fir beetle damage in the future. That’s because with hotter, drier summers, trees will be living in more stressful conditions; and as extreme weather events such as storms become more frequent, major windthrow episodes which precipitate beetle outbreaks could become more common.

The intensity of Swiss needle cast in any given year is often weather dependent. Map: Swiss Needle Cast Cooperative

Diseases:  Swiss needle cast can be found everywhere in western Oregon, but currently it only impacts tree growth on the west side of the Coast Range and a few isolated spots in the Cascade foothills. That’s because for the fungus to thrive and spread it needs warm, moist conditions in the winter and spring like those along the foggy coast. These types of conditions are likely to be more common in the future, so Swiss needle cast severity is likely to intensify in the areas where it is currently a problem. Whether the impacted zone will expand eastward is less certain.

Invasive species:  Exotic species of plants, insects, and pathogens are introduced all the time through the commerce and transport of live plants, wood packing material (such as pallets and crates), and firewood. Some of these become invasive and create huge problems (see: sudden oak death). The Oregon Invasive Species Hotline is an easy way for anyone to submit a report of an unfamiliar plant or insect that you think might be an invasive species. An expert will review your report and respond appropriately.

Browsing animals:  There is an interesting and complicated study now in its sixth year, looking at the interaction between herbicide use in young plantations and deer and elk browse. Thomas Stokely, a PhD candidate at OSU explained the results. Some, including myself, have wondered whether reducing herbicide use after a clear-cut could help reduce deer and elk browse on seedlings, because there would be other forage for them to eat. However, in Thomas’s study, seedlings were browsed regardless of the level of herbicide application. And, where it was applied lightly, seedlings didn’t perform as well, due to the double whammy of being browsed and competition from other vegetation.

Are more trees dying in Oregon?  The perception around here may be “yes”, but the research says “no”. Forest mortality rates have remained relatively constant (around 2%) since the late 1990’s, says Andy Gray of the US Forest Service.

With that, I feel a little more educated about forest health for the time being, and I hope you do too. May your forests be healthy…and resilient.

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