Helping Landowners Learn From Their Peers About Harvest Options

Northwest Natural Resource Group and Oregon State University are reaching out to forest owners for a voluntary study about timber harvesting methods to understand how they affect both financial and forest health outcomes.

The goal of this research project is to help landowners who are considering a timber harvest to learn from the experiences of others. There is limited information about the economics of commercial timber harvests that use thinning or uneven-aged management, and how those results compare with other harvest methods.

The researchers are looking to survey Oregon and Washington forest owners who harvested timber from their forest in the past five years (since 2014) and are willing to share information about the silvicultural methods and financial outcomes from these recent timber harvests. The survey asks detailed questions about the harvest techniques and equipment used, the volume of timber harvested, cost of the harvest work, and the harvest revenues.

The results of this study will be shared with forest owners through a variety of methods including articles, papers, and classes taught by NNRG, OSU, and partner organizations. Data in the study will remain confidential within the research team. Information will be aggregated so it cannot be traced to any individual ownership. Data will be collected from through June 2019.

If you are willing to share recent harvest information with NNRG and OSU, contact Lindsay Malone, one of the project researchers, at Lindsay can provide you with a copy of the survey.

Learn more about this research project at

Lindsay Malone, Director of Programs, Northwest Natural Resource Group,

Tree Profile: Red Alder

Red alder (Alnus rubra) is the most common hardwood species in the Pacific Northwest.  For a long time, in fact, many people might have said that it was a little too common.  Having little monetary value, growing where nobody particularly wanted it, and often times out-competing more commercially viable species, red alder has had a long-standing reputation among tree farmers as an opportunity for chainsaw practice.

However, things have changed over the last few decades and alder wood can now be worth nearly as much as Douglas-fir.  Not to mention it can be managed on shorter rotations, adds nitrogen to the soil, and can tolerate wet sites where many other species grow poorly.  Coming from the Midwest, where alder only grows as a shrub, it has been very interesting to learn about the ecological and economic potential of alder for forest owners.  With this potential in mind, I thought it might be worthwhile to give a detailed profile of this tree and clear up some common misconceptions.

Distribution and Ecology

Red alder ranges in a long stretch along the Pacific coast from as far south as southern California to its northern extent in southeast Alaska.  Some patches of it can be found on north-facing slopes in northern Idaho and western Montana, but for the most part it enjoys low elevations west of the Cascade Mountains.  The best tree development occurs below 1500 feet in Oregon, Washington, and British Columbia (Harrington, 2006).

Under natural conditions, alder moves in first after a stand-clearing disturbance (fire, flood, large wind event, etc.), whichmakes it what forest ecologists call a “pioneer species”.  In unmanaged settings, it requires bare soil to establish and plenty of light to grow, so it’s rarely seen growing underneath an existing canopy.  It’s a fast grower, and achieves the majority of its height growth in the first two decades after establishment.  Additionally, alder is part of unique group of plants known as “nitrogen-fixers” that create symbiotic relationships with soil bacteria to transform atmospheric nitrogen for the plants use.  This allows it to establish on sites with limited nitrogen, such as new or highly disturbed soils.  Over time as natural succession continues, alder often gives way to shade tolerant species like western hemlock, red cedar, and Sitka spruce.  Typically living less than 100 years, alder has a relatively short lifespan.  So compared to other pioneer species like Douglas fir, which can often live to be 600 years old or more, alder is the “live fast, die young” tree of Pacific Northwest forests.

Silviculture and Management

It’s commonly known that red alder enjoys wetter soils.  Most forest owners can attest to this, as they’ve seen it take over their stream sides, ditches, and any other perennially moist sites.  While it’s true it is rarely found on drought-prone soils, it’s very important to recognize that it is also not a fan of overly wet, poorly drained soils like some species (i.e. ash, cottonwood).  For this reason, choosing a site where alder will grow into a valuable product can be difficult but is possibly the most important management step towards producing high quality logs.

A common phrase to hear among some foresters and tree farmers is that “anywhere Doug-fir will grow, alder will grow too”.  While there is truth to this, it’s not the entire story.  Just because alder will grow on a site, doesn’t mean it will grow well.  Table 1 shows some basic characteristics of a good alder site.

Table 1.  Characteristics of good and bad alder sites
Traits of Good Alder Sites Sites to Avoid Planting Alder
Elevation less than 1500ft Bogs or marshes
Lower slopes, flood plains, benches Upper slopes
West to east slopes South to southwest aspects
10-30% slope Frost pockets
Moderately well to well-drained soil Sandy, excessively drained soils
Silt loam, silty clay loam, clay loam, silty , clay Poorly drained soils
Soil depth greater than 30″ Sites with excessive weed competition
Depth to summer water table <10′ Exposed or windy sites
Source:  Dobkowski, 2006

If you’re interested in the financial return of growing alder, the best prices come from trees with large-diameter boles and few lower branches.  Getting alder to grow this way requires planting densely.  The competition with nearby trees forces alder to grow upwards quickly rather than growing laterally and creating a thicket of branches.  Recommended planting density is between 540 – 680 trees per acre (or a spacing of 9’ x 9’ or 8’ x 8’), although some plant lower where natural regeneration is likely.  And while you don’t need bare soil to plant alder trees, you will likely have to control competing vegetation.  A critical metric for successful alder management is the first year of growth.  Alder can reach 50% of its maximum height within 15 years, with the fastest growth rates occurring in the first 5-7 years (Harrington, 2006).  So if your trees aren’t shooting up out of the ground something is wrong, and it’s likely your site.  This early growth is critical to get out from under other competing vegetation (i.e. Scotch broom), which can stunt growth and kill seedlings.

How you manage your alder after it is established is going to depend a little on your goals.  Are you in it for timber?  Are you interested in its wildlife benefits? Are you looking for smaller logs to fuel your mushroom growing operation?  Heck, maybe you’re just growing it just because you like the look of it.

Alder requires a live crown ratio (the proportion of the stem with living foliage) of about 50% to maintain vigorous growth, where trees like Douglas fir can get away with 40% or even 30% at times.  Since it grows so fast, alder crowns in a densely planted stand can get below 50% as early as 7-10 years, depending on the site quality.  This is where your management goals come in.  If you’re not cash-driven and want to take a more hands-off approach, thin heavily and leave it be.  You can remove about 70% of the stems (down to around 150 trees per acre).  This will keep you from having to do another thinning down the road and you will still produce a fair amount of volume at the time of final harvest.  If you want more volume, thin lighter to about 250 trees per acre (or about 50% of the stems).  This will give you a little more volume to play with for a final harvest and possibly a commercial thinning before then.  The basic gist here is to plant alder densely to minimize the retention of lower branches and thin hard to maintain crown ratios.  The main difference between managing alder and managing conifer species is that you have to do it earlier and more frequently, which requires actively monitoring your stands.  If you play your cards right, choose the right site, and don’t miss your thinning windows, you could have an alder harvest as early as 30 years on really productive ground.  A quick, but important, note: don’t leave valuable alder logs on the ground after cutting.  Alder decays quickly.  So if you’re going to harvest, make sure you have a plan to get them to the mill quickly.

This is a short, sweet, and fairly rosy summary of even-age alder management, so I encourage you to check out the sources at the end of this article to get more in-depth information on alder silviculture and potential pitfalls.  Additionally, I know it is likely that the majority of landowners reading this are not sitting on an empty plot waiting to be planted.  Instead many are dealing with existing, and likely decadent, stands of alder.  These stands are common throughout western Washington and are a result of intense logging without replanting in the mid-20th century.  Intervening at this point is complicated and depends largely on your goals as the landowner.  If you are purely cash-driven, it can often be the most efficient choice to simply cut down the decaying alder and start over.  Thinning in these older stands provides little benefit to tree growth since crown ratios are typically small and trees are reaching the end of their lifespan.  However, many landowners aren’t motivated by income and instead are driven by a love of wildlife, aesthetic appearance, or recreation and consequently may be interested in developing more complex forest systems.  Your options for management can range from light-intensity thinning of the alder overstory to underplanting shade-tolerant species, or even doing nothing at all.

However, it is important to note the risk of doing nothing.  On occasion, the dense shrub layer that often exists in pure alder stands can inhibit regeneration of shade-tolerant conifers below and leave you with a thicket of shrubs after the alder dies.  To learn more about options for existing alder stands, try the WSU publication Management Options for Declining Red Alder Forests (PDF) by Kevin Zobrist.

It is also important to note that because it can tolerate wet sites, many existing stands of alder may be in Riparian Management Zones (RMZs).  It goes without saying, but your management choices are much more limited in these areas.  However, some options, such as converting alder to longer-living conifers (AKA a “hardwood conversion”), allow for management in these areas.  Contact the Washington DNR Small Forest Landowner Office to learn more.

Market and Uses

In the first half of 2018, the market value of red alder in the Washington coast market area has averaged around $720 per mbf (1,000 board feet).  Compare that to Doug fir, which has averaged about $745 this year. Clearly the market has changed since the 1990’s when alder was regularly worth less than $250/mbf.  And better yet, it’s showing no signs of slowing.  While the timber market is and always will be volatile and unpredictable in the long run, it seems that prices for quality alder saw logs are going to be competitive for the foreseeable future.

Alder is used for a variety of end products because of its wood characteristics and availability in the marketplace.  It has a reputation for being easy to machine, glue, and finish.  While it ranks low in durability and hardness, it is prized for its grain and appearance.  It’s often used for veneer, furniture, cabinets, paneling, doors, and food dishes.  Lower quality logs are often used in pulp products like tissue and paper.

Alder has many uses beyond traditional wood products.  Small diameter logs serve fantastically for mushroom growing material. The bark contains salicin, which is a chemical similar to aspirin that can be used to cure headaches and other
maladies. Native Americans often used alder for dyes, baskets, medicine, and even used the dried bark as soup thickener.

In terms of wildlife, birds welcome the fact that alder seeds stay on the tree throughout the fall and winter, when food is scarce.  Additionally, the dense shrub layers provide forage and habitat for a multitude of wildlife species.  Deer and elk also love the leaves, twigs, and buds (much to the frustration of tree farmers).


Alder is the best bet for a forest owner interested in hardwood management and its potential is remarkable both because of its vigorous early growth and ability to add nitrogen to the soil between conifer rotations.  If you’re a landowner and you’re hesitant to commit to growing alder, it’s understandable.  It has a long history.  And ultimately red alder is less forgiving than species like Douglas fir, so it may not be the right choice for an absentee landowner.  But many tree farmers have experienced planting conifers in an area, only to have them overtaken by naturally established, faster-growing alder.  In my mind, these are sites predestined for alder production and a great way for all types of forest owners to dip their toes in alder management (provided they are not in RMZs!).  After all, why fight it?  Now that it’s worth as much as other species, why not take advantage of what the site is doing already?

Learn More:

Works Cited:

Dobkowski, A. (2006). Red Alder Plantation Establishment: Site Selection, Site Preparation, Planting Stock, and Regeneration. In R. Deal, & C. Harrington, Red Alder: A State of Knowledge (pp. 87-94). Portland, OR: U.S. Department of Agriculture – Pacific Northwest Research Station.

Harrington, C. A. (2006). Biology and Ecology of Red Alder. In R. Deal, & C. Harrington, Red Alder – A State of Knowledge (pp. 21-54). Portland, OR: U.S. Department of Agriculture – Pacific Northwest Research Station.

Patrick Shults, Extension Forester, Washington State University,

Does Chipping Pine Attract Bark Beetles?

Lop and scatter method of slash disposal
Lop and scatter method of slash disposal. Photo: USDA

As many forest landowners already know, pine slash has a tendency to attract pine bark beetles. There are several recommendations for slash disposal to mitigate this problem. Two common methods — lop and scatter, and chipping — focus on eliminating bark beetle habitat while retaining the nutrients contained within the slash on site.

The lop and scatter method involves cutting slash into smaller pieces (less than 12 inches in length, less than 3 inches diameter) and scattering the pieces throughout the site. Chipping involves running slash through a chipper and scattering it throughout the site, similar to lop and scatter. While there is no chance that bark beetles can infest the chips, it is still possible for bark beetles to infest the pieces in the lop and scatter method. The chances of the beetles being able to successfully produce brood in these pieces is pretty low, as they will likely dry out before the larvae are finished developing. Both methods are a reasonable substitute to piling and burning when burning is prohibited, BUT…

Anytime you cut pine, you are releasing volatiles. Volatiles emitted from pine contain chemicals called monoterpenes. Some monoterpenes have been shown to attract bark beetles and are often included as part of the lure when trapping for bark beetles.

female bark beetle
A female bark beetle eating the phloem of a tree. Photo: USFS

If you are choosing between lop and scatter and chipping, which is best? You would think that chipping would be the better choice since there is no chance that bark beetles can infest the chips. But a study by Fettig et al. (2006) showed that chipping in ponderosa pine stands attracted bark beetles more so than the lop and scatter method, particularly in the spring. Why would this be? As it turns out, directly following treatment chipping releases much larger quantities of attractive monoterpenes than the lop and scatter method. If large quantities of attractive monoterpenes are released at a site where the slash has been chipped and bark beetles arrive, where are they going to go? They cannot infest the chips. They are going to go to the standing, residual trees. Although the act of thinning should increase the health and vigor of the residual trees, it will take at least a year for those trees to respond, therefore, you may wind up with bark beetle infested leave trees.

So, does this mean you cannot chip? Not necessarily. Some landowners prefer to begin thinning treatments on their property in the spring; it is finally warm (but not too warm), the snow is melting off, and they are ready to go outside and get things done. Other landowners find that they have to thin in the spring for various reasons (the snow is too deep during the winter; fire season often prohibits the use of machinery in the summer; contractors cannot fit everyone in during the bark beetle “off” season). Unfortunately, as Fettig et al. (2006) found, the response of bark beetles to high concentrations of volatiles released from chips is more significant in the spring because a large segment of the beetle population is most active during this time.

If you plan on chipping, it would be best to avoid treatments in the spring. The best time to chip (or do any sort of management that releases pine volatiles for that matter, including pruning), would be in late summer (late July/early August) through early winter (December). When producing chips, avoid piling them and absolutely do not pile chips at the base of any residual trees.  Spread the chips out in the sun if you can. The quicker they dry out, the quicker the volatiles will dry out, and the less overall bark beetle risk there will be.

By Melissa Fischer, forest health specialist Washington State Department of Natural Resources, Northeast Region,


Fettig, C.J., J.D. McMillin, J.A. Anhold, S.M. Hamud, R.R. Borys, C.P. Dabney, and S.J. Seybold. 2006. The effects of mechanical fuel reduction treatments on the activity of bark beetles (Coleoptera: Scolytidae) infesting ponderosa pine. Forest Ecology and Management. 230: 55-68.

Forestland Grazing in the Inland Northwest

Many of the cultural practices that family forest owners use to improve forest production may be used to improve other components of their forestland. Forest owners may wish to increase production of grasses and forbs for livestock production and/ or wildlife habitat improvement. Forestland grazing presents opportunities to increase land productivity, improve cash flow, and to increase the diversity of plants and wildlife – all of which are not mutually exclusive. Most forestland grazing is found on the east side of the Cascade Mountains, as forest stocking levels tend to favor more open stand conditions. While generally discouraged by foresters due to soil impacts on water-saturated soils, limited forestland grazing is found on the west side of the Cascades, and generally on sites that are managed to promote more open stands.

PHOTO: T. Hudson, WSU
Photo: T. Hudson/WSU

Grazing can benefit forest management in several ways. For example, grazing and browsing can reduce the need for herbicides and mechanical weed control, and manure can reduce the need for fertilizer application by promoting nutrient recycling. Forest stands that include grazing as a management option are often park-like in appearance, and generally more socially acceptable than traditional plantations managed exclusively for timber. Low-intensity cattle grazing-grazing reduces competition for moisture between overstory trees and understory shrubs when the stand is very young. Studies in Oregon have shown up to 50 percent increase in forage and timber growth over 10 to 20 years with the integration of livestock into the system. Also, adding nitrogen-fixing vegetation such as legumes to the forage mix combined with recycled nutrients in dung and urine increases nitrogen uptake of trees on sites that are naturally deficient of nitrogen.

Weight gains for cattle on forested pastures may exceed those of grasslands because: (1) prolonged spring run-off provides more spring moisture to understory plants, (2) forage reaches maturity more slowly, (3) grasses are protected from sun and frost curing, and (4) forage species diversity provides a longer grazing season. Experience has shown that forests also protect cattle from weather – cutting the direct cold effect by 50 percent or more and reducing wind velocity by as much as 70 percent. Cattle protected by windbreaks gained 35 lbs. more than unprotected herds during a mild winter and lost 10.5 lbs. less during severe winters. Weight gains also improve with proximity to shade.

Livestock grazing in forests is much more common than many people realize. In a recent survey, 26 percent of Washington family forest owners reported livestock grazing on their forestland in the previous 12 months. Nationally, livestock graze about 25 percent of all forests. This forest area accounts for about 13 percent of the total land grazed in the U.S. and roughly equals the total area of improved pastures and grazed croplands, combined.

Foresters often discourage livestock grazing in timber plantations for fear that trees will be browsed, debarked, or stepped on. Once reassured that the plantations can be safely grazed without damaging trees, the next silvicultural concern is often soil compaction. Cattle, sheep, goats and other livestock can exert as much downward pressure on soil as do agricultural tractors and unloaded forestry harvest equipment. When a sustainable number of animals are managed, trampling only occurs over a limited area. In addition, soil compaction by livestock is generally confined to the top few inches of soil whereas heavy equipment can compact to depths over a foot. Extensive reviews of published literature found that grazing does compact soil—though it is unusual for livestock grazing on drained soils to sufficiently compact soils to hinder plant growth. Forested rangelands in the western U.S. are most frequently used as summer-fall range, when soils are not saturated. It is unlikely that responsible forest grazing will sufficiently compact soils to reduce tree growth unless soils are poorly drained.

Photo courtesy of Cornell University
Photo courtesy of Cornell University

Large seedlings are cost-effective in forest grazing systems. While more difficult and expensive to plant, these trees have a higher tolerance to damage from livestock and will more quickly escape the maximum height of browsing by livestock and deer. Careful management should be the norm when grazing young stands, particularly on steep slopes to see that soil is not displaced by animal hoof action. The number of trees to plant and the planting pattern vary widely with the objectives of forestland grazing. If the forest component is to be emphasized, stocking of 200 to 400 trees/ acre are common, with grazing restricted to the first decade or so after tree planting. If grazing is to be maintained over the long-term, lower tree stockings will be needed to maintain forage production with subsequent overstory tree thinning that reduces stocking to as few as 50 trees/ acre at maturity. Tree pattern becomes increasingly important as density increases. Conventional forests use rectangular grids of trees to minimize competition between trees at the expense of the understory vegetation. Square grids, single, double or triple rows, and cluster plantings have all been used in grazed forests. The grid layouts optimize the area for tree growth, while the row or cluster plantings share the site resources more evenly with the forage crop. Rows support greater understory forage and the ease of access to row plantings for agricultural operations such as fencing, fertilizing, haying, etc., make them popular with producers.

Deer photo by E. Gutierrez/WSU
Photo: E. Gutierrez/WSU

Overgrazing can lead to the removal of terminal leaders, substantial lateral branch defoliation and, more rarely, debarking. Young conifers are fairly tolerant to defoliation provided that the terminal leader is left intact. Research applicable to eastern Washington forests reported that heavy lateral branch defoliation of 4-year-old Douglas-fir did not affect tree height and reduced the current year’s growth by only 1.5 percent compared to undefoliated trees. It takes browsing of over half of the needles produced in the current year or girdling of over half of the stem to visibly reduce long-term growth. Removal of terminal leaders is a more serious matter. Loss of conifer terminal leaders not only forgoes that year’s height growth, it may also reduce diameter growth by as much as 30 percent. The risk of growth loss and tree deformation of young conifers in pastures is high enough to warrant either careful monitoring of forage availability and livestock grazing behavior, or physical protection of the trees during the first few years after plantation establishment. Given the increased competition from other trees and understory shrubbery on west side Cascade forests, the loss of a year’s height growth may eventually result in competition mortality. However, to place these concerns in perspective, studies in western Oregon forests report that native deer inflict more damage to young forests than livestock.

While livestock can graze new plantations safely, great care should be exercised when tree terminal leaders are within the reach of livestock. Pastures can be grazed during the spring growing period with negligible defoliation of trees provided that total utilization of forage does not exceed 35 percent of current seasons forage crop.

Tree damaged by deer.
Tree damaged by deer browsing. Photo: A. Perleberg/WSU

The potential for tree damage by livestock appear to be related to several factors including season of year (spring/ early summer is when other forage plants are most palatable, but compaction may be an issue), percent utilization of forage available, age of animal, and tree heights. One study in southern Oregon comparing tree seedling growth by cattle grazing in a recently planted pine plantation versus a non-grazed plantation, experienced enhanced tree growth due to both the reduced grass and shrub vegetation competition the with the pine seedlings as well as the nitrogen inputs from manure. Damage is more likely during the first two-three years of tree growth before resinous chemical defenses are well developed. After three years, conifer foliage is not particularly palatable to cattle or elk, though sheep, goats, and deer might still be attracted. Conifer foliage is most likely to be grazed in the spring when it is newly-emerged and the anti-herbivory defense compounds have not yet fully accumulated, or any time that livestock are short of other forage, however, livestock will consume conifer foliage in low amounts even when other preferred forage is available. This very low level of tree browsing often changes quickly info substantial levels as other forage is depleted. It is not unusual for over 90 percent of tree defoliation to occur when other forage choices are limited. Livestock grazing young forests must be checked frequently and animals properly removed when forage is depleted and they begin to actively feed upon trees.

Minimizing Livestock Damage

In general, livestock breed is not a useful predictor of damaging feeding behavior as is age, sex, and past experience of animals. However, larger breeds such as Charolais, Semmental; Gelbvieh, and Limousin tend to distribute less than smaller breeds, so concentration in areas such as riparian forests can become an issue with their tendency to linger that can lead over-grazing and potential damage to soil structure. Older dry ewes do far less damage to trees than young lambs or rams. Cattle, sheep and goats that have consumed either green foliage or dry needles regularly in the past are much more likely to feed upon young trees in pastures. In every flock or herd there are individuals that seem to be predisposed to feed upon trees. Feeding behavior may be taught to others. Tree damagers should be culled as soon as they are identified. Some practitioners also report that livestock transported into grazed forests from non-forested areas will browse young trees as a “novel” food. Fencing, tubing, repellents and livestock exclusion have all been used to control browse damage by both wildlife and livestock in grazed forests. Fencing works well when trees are concentrated in closely spaced rows to maximize grazing area and minimize fencing costs. Fencing can be permanent where continuous grazing is planned or wildlife damage to trees is a concern. Portable electric fencing has been successfully used for short time periods and prescriptive grazing to reduce invasive plants. Lightweight portable fencing is erected quickly when and where needed to protect trees from livestock, so monitoring of the grazing progress is not as critical as with open grazing. Protecting individual seedling trees with plastic mesh or rigid tubes has also been used successfully, but this measure has drawbacks. Cattle trampling and tube removal by sheep and subsequent browsing of the unprotected tree is a real concern, so monitoring of the grazing is required. Attaching the tube firmly is another problem. Rigid wood stakes often break when rubbed by livestock. Resilient materials such as bamboo are more resistant to breakage.

Riparian Area Concerns

Livestock grazing becomes more complicated where riparian systems are involved. Because riparian areas remain lush and green into the summer dormancy period for upland grasses and forbs, livestock will congregate in these areas for shade, water, and forage. This situation could result in overgrazing of riparian plants critical for riparian and stream function and physical damage of stream banks. Some rules of thumb include:

  • Allowing continuous, season-long grazing will damage riparian function.
  • Expect that in years of good rainfall, an early growing season for grazing vegetation will encourage cattle to graze uplands, where green forage and warm temperatures are more favorable.
  • Install off-stream water and salt far away from riparian areas.
  • Cull animals that prefer to “camp” in riparian areas.
  • Force cattle out of riparian areas with riders or substitute with herded sheep or goats.
  • Exclude riparian grazing until late in the growing season, but be careful to watch for overuse of woody plants.
  • Expect mixed or very site-specific results for riparian pastures in rotation systems.
  • A number of successes have been observed when late winter and early growing season grazing systems were merged, but be careful to monitor compaction.
Cattle grazing in riparian area
Cattle grazing in riparian area. Photo: T. Hudson/WSU


Livestock management is the key to successful forestland grazing. Important considerations for proper grazing management include where the livestock graze, season of use (timing), length of use (time), and the amount of plants grazed (intensity). Some rules of thumb include:

  • Match the type of livestock to the forage base.
  • Make judicious use of fencing, salting, off-riparian water, and trails to aid proper distribution and minimize damage.
  • Customize rotational grazing systems to the local area and manage them intensively; time and timing will vary depending on the location, year and objectives.
  • Move livestock well before browsing begins on trees.


By Andrew B. Perleberg, Regional Extension Specialist – Forestry, Washington State University and James P. Dobrowolski, Rangeland, Grassland, and Water Quantity National Program Leader, National Institute of Food and Agriculture, USDA.

Potential for Douglas-fir Beetle Outbreaks in Eastern Washington

Douglas fir killed by bark beetle
Beetle damage in stand of Douglas fir. Photo: Kenneth E. Gibson, USDA Forest Service,

Several windthrow events in 2015 have paved the way for a potential outbreak of Douglas-fir beetle in areas of eastern Washington this spring (2017).

Douglas-fir beetle egg and larval tunnels
Characteristic pattern of Douglas-fir beetle egg and larval tunnels. Photo courtesy of Oregon Department of Forestry.

The Douglas-fir beetle is a bark beetle that normally breeds in felled, injured, windthrown or root-diseased Douglas-fir. It may also attack western larch, but can only produce brood in downed trees. At outbreak levels, this bark beetle can attack and kill large diameter, healthy Douglas-fir. Outbreaks tend to occur after extensive windthrow events such as was seen in 2015. Outbreaks may also occur after defoliation events, fire and extended drought. Dense stands surrounding areas where windthrow, defoliation, fire and drought events have occurred may be at high risk for an outbreak, particularly if those stands contain a 50 percent or more component of Douglas-fir that are greater than 120 years of age and larger than 14 inches DBH (DBH = diameter at breast height; diameter of a tree bole 4.5 feet from the base).

The Douglas-fir beetle has one generation a year. Brood that developed through 2016 will pupate and emerge as adults this spring. Once emerged, they will begin attacking standing trees surrounding the windthrow, as the windthow is no longer habitable for them.

What can be done?

The best approach to prevent an outbreak this spring is to salvage any large diameter Douglas-fir or western larch that were downed by the storms prior to the adult beetle flight, which should occur in April, depending on temperatures. Windthrown trees can also be burned or chipped on site if salvage is not an option. Time is running out; if you find you cannot take care of this material, the use of the anti-aggregate pheromone MCH is another option.

A pheromone is a chemical released by bark beetles that is used to affect the behavior of other beetles of the same species. Aggregating pheromones attract beetles, while anti-aggregates repel them. A bark beetle might use an anti-aggregate to prevent overcrowding within a tree. An anti-aggregate basically tells other beetles that there is no room for additional inhabitants in the tree.

MCH bubble capsule stapled to a tree
MCH bubble capsule stapled to a tree. Photo: US Forest Service.

The Douglas fir-beetle naturally produces an anti-aggregate to repel others. A synthetic version of this anti-aggregate, MCH, has been produced and is available for purchase through several online companies. MCH comes in a “bubble capsule” and can be used to protect individual live, high-value Douglas-fir or even an entire stand. For individual tree protection, two bubble capsules can be stapled on either side of a Douglas-fir bole at approximately 6-8 feet from the ground for a tree less than 24 inches DBH. Four bubble capsules should be used for Douglas-fir larger than 24 inches DBH. To protect a stand of Douglas-fir, 30 bubble caps per acre can be evenly placed through the stand.

MCH costs approximately $2.50 per capsule and should be hung prior to the beetle flight in April. It is advisable to contact your local forest health specialist if you are considering this method of management. Additional information about this method can be found in the free publication, “Using MCH to protect trees and stands from Douglas-fir beetle infestation,” published by the US Forest Service.

By Melissa Joy Fischer, forest health specialist, Washington State Department of Natural Resources,