The summer edition of Tall Timber Topics is now available. Click here to download and read it. In this issue:

  • Considering logging? Read this first
  • Green alder sawfly
  • Summer calendar of events
  • Blackberry management
  • Ask an Expert
  • Information about upcoming Washington County Extension Office move

Thursday, July 7th, 6:00 – 9:00 pm
Forest Grove
“Keeping Your Little Trees Growing”

This gathering will be an opportunity to talk about reforestation challenges and strategies to keep your planted seedlings growing strong. What’s worked (and not worked) for you? Come ready to share your experiences with weed control, animal damage, insects and diseases, and other concerns. We will look at some young trees of several species planted by host Robin Lindsley on her small property, and talk about her efforts to get them “free to grow”.

Whether you are new to managing your land or a seasoned pro, all are welcome and encouraged to come. WOWnet events are designed for participants to learn from one another. And who doesn’t like a potluck in the summer!

For details and directions, view the flyer.


By Paul Oester and Dave Shaw, OSU Extension Service

A native of Europe, North Africa and the Near East, the green alder sawfly (Monsoma pulveratum) (Hymenoptera: Tenthredinidae) was first found in North America in eastern Canada in the early 1990’s, then in Alaska in 2004.  More recently, the green alder sawfly was identified in trap samples in nine Washington counties and one Oregon county (Multnomah).  Examination of insect collections at Western Washington University indicates that this insect has probably been present since 1995.  It was first detected in the contiguous United States on understory shrubs in Vancouver, Washington in April 2010.  We don’t know a lot about this insect but we are beginning to tease out how it operates.

green alder sawfly larva
Figure 1: Green alder sawfly larva (photo by Jim Kruse)

How do you identify this critter?
Adults emerge from overwintering sites in the soil or dead wood in the spring and lay eggs on expanding alder leaves.  New larvae are very pale green and 2-3 millimeters long.  Over time, as the larvae mature, they become a vibrant green (Figure 1).  When fully grown larvae are about 15-18 millimeters long, a little more than ½ inch.  The adults look like a small wasp, and the females (males have not been recorded in North America or the UK) have a black head and antennae.  The middle (thorax) of the adult insect is black, sometimes with some yellow or brownish coloration; their legs reddish brown to black and abdomen black with the margins of the segments white to yellow (Figure 2).

green alder sawfly adult
Figure 2: green alder sawfly adult (photo by Andrei Karankou)

Life history
A pre-pupal stage overwinters and pupation occurs in the spring.  After the eggs hatch in the spring, larvae feed on alder leaves through the spring and early summer, then typically drop to the ground to pupate in the soil.  In Europe and recently observed in Alaska, these insects have been reported to also burrow into rotten wood to pupate (Figure 3).  Just another reason not to move firewood interstate.

What about potential impacts?
Not much is known about how this insect will fare on red alder in western Oregon and Washington, as well as other species throughout these two states.  In Alaska, this species has been feeding primarily on thinleaf alder (Alnus tenuifolia).   There is some concern that the feeding of the green alder sawfly, woolly alder sawfly and the striped alder sawfly combined with stem cankers may lead to reduced nitrogen inputs by alders and perhaps alder mortality.

green alder sawfly pupal niches
Figure 3: green alder sawfly pupal niches (photo by Jim Kruse)

In the Pacific Northwest, several insects feed on alder species so these may compete for host foliage and the additional feeding by the introduced sawfly may have a minor effect.  However, the green alder sawfly begins feeding earlier in the spring than other species and could effectively outcompete native species if foliage becomes limited.  Another concern is the native parasite/predator complex: will these make the switch to the new invader?

What to do?
Efforts by federal and state agencies will include trying to delimit the extent of the sawfly’s distribution and encouraging more monitoring as well as research and education.  The US Forest Service point person for this invasive insect is Kathy Sheehan, based in Portland.  She is coordinating the effort to determine the distribution of the green alder sawfly in Oregon and Washington.  They have already set up trapping sites throughout western Oregon in particular.  Eradication is not a feasible option because of the widespread distribution of detections in Washington and Oregon.  The fact this invader can potentially pupate in dead wood is another reason to manage the distribution of firewood and keep it local.

The bright green larvae are distinct.  If you are out and about in your forest, look for these critters on alder leaves and if you find any likely suspects contact Amy Grotta at the Extension office, 503-397-3462, Dave Shaw, OSU Extension Forest Health Specialist ( at 541-737-2845, or Kathy Sheehan ( at 503-808-2674.  For more information, go to

Green Alder Sawfly.  2010.  Forest Health Protection, Pacific Northwest Region, USDA Forest Service.  4 pages.

New Pest in Alaska and Washington: The Green Alder Sawfly-Monsoma pulveratum (Retizius).   2010.   Pest Alert.   USDA Forest Service State and Private Forestry Alaska Region.  R10-PR-002.  2 pages.

panoramic view from Chehalem Ridge
Panoramic view from the top of Chehalem Ridge (click picture to enlarge)

Last month I was fortunate to have the chance to tour the Chehalem Ridge Natural Area, a 1,100 acre property acquired last year by Metro near Gaston. It was a fascinating field trip led by Kate Holleran, who is responsible for directing forest management for Metro at Chehalem Ridge.

Kate described Metro’s management objectives, which include restoring oak woodlands through thinning and release from conifer competition; thinning the extensive, dense stands of young Douglas-fir to improve forest health, productivity, and forest structure; maintain the property’s extensive road network; and protect and improve fish and wildlife habitat. Kate hopes that Chehalem Ridge will be managed as a working forest, with revenues from product sales going back into forest management activities.

Chehalem Ridge is currently not open to the public except through guided tours. Luckily, Washington County Small Woodlands Association has arranged for a tour on August 27th. I look forward to seeing what develops at Chehalem Ridge in the coming years. I think it could be a great local resource to demonstrate forest management for multiple objectives. 

Spring seems to be late in arriving this year, and so is the spring edition of our newsletter, Tall Timber Topics. But here it is at last. In this issue you will find information on new publications on soil management, weed management for Christmas trees, new online forest maps, and a calendar of upcoming events.

Producing, printing and mailing a newsletter takes time. I’m hoping that this blog will be a means of getting information out in an easier and more timely way. But for those who still prefer or rely on a printed source of information, rest assured that Tall Timber Topics is not going away.

A whole bunch of happenings of interest in our areas in the upcoming weeks. Here’s the rundown:
Sat. April 16th, 9 am – 2 pm: Oregon Woodland Cooperative Annual Meeting. Kinton Grange. Members expected, visitors are welcome. Lots of updates on Co-op activities and a potluck lunch.

Tues. April 19th, 6 – 8 pm: Build Local Alliance Spring Showcase. Portland. The event is free and open to the public who are interested in sourcing and utilizing local wood products.

Tues. April 26th, 6:30 pm: Washington County Small Woodlands Association meeting. OSU Extension office in Beaverton. Charlie LeFevere, well-known Oregon truffle expert, is the guest speaker.

Sat. April 30th, 5:30 pm: Columbia County Small Woodlands Association meeting. Beaver Homes Grange. Bruce Alber will speak on herbicide applications for forestry. Dinner beforehand; call 503-556-2014 to RSVP.

It’s nothing new for this time of year, but we sure have seen our share of precipitation lately. While we’ve likely seen the last of the snow (finally), more wet weather is in store. Good for planting trees, but maybe causing problems on your roads. Out in the field over the last several weeks, I’ve seen plenty of issues with roads. Here are some examples.

Example #1: A landowner has a steep, winding access road that leads from her house down to her pasture. Adjacent to the road, a culvert underneath a county road feeds into a small field. But heavy rain washed sediment and gravel off the county road and it collected in front of the culvert, diverting water from the field onto the landowners’ access road. Because the road had not been designed with water diversion features, severe erosion ensued. Lesson: Get the water off your road as soon as possible. Use ditches, waterbars, and cross drains to do so.

Example #2: The sidecast fill failed on an industrial haul road high up along a steep slope, sending a landslide that reached almost down to the fish-bearing stream that the landowner had been working hard to restore. In this case, the road was an old one that would have been designed differently under today’s standards, and if it were not for the need to access a harvestable unit in the near future, the landowner would have closed this road a while back.  Lesson: Old roads are often the worst. If you have an old road that is no longer needed, consider closing and restoring it.

Example #3: Busy beavers have created a pond directly upstream of a culvert on a landowner’s property. A timber company has a road easement to access their land in back of this property, and they dynamited the beaver dam in the past to protect the culvert and the road. But the beavers came back, and the pond is even bigger than before. Now the landowners are concerned that a big rain could cause the culvert to plug and the road to fail. Lesson: No easy solution here. Nature’s engineers are crafty. Re-engineering the stream crossing may be the long-term (but expensive) solution.

If any of these situations sound familiar, or if you have other road issues, check with the friendly folks at the NRCS and Soil and Water Conservation District office. They might have some technical and financial assistance to help you out and protect our watershed health at the same time.

Longtime woodland owners always seem to have interesting stories to tell, and it seems like local writers are picking up on that. I just came across a story on Country Traveler Online about the VanNatta family and their tree farm outside of Rainier. This website says that it is  meant to “entice people to travel more in Oregon”. I wonder how many of these people will try to make it down the VanNatta’s driveway…

A couple of months ago, the Keasey family of Vernonia was featured in a long article in The Vernonia Voice. This family is now in the seventh generation of owning their land. Wow!

It’s great to see stories like these pop up in places where the public can learn what family woodland ownership is all about.

This is the big weekend for tree sales. Here’s the rundown for three sales, all happening Saturday, March 12th.

Columbia County Small Woodlands Association tree sale: 9:00 am – 2:00 pm at Lawrence Oil in St. Helens. Bareroot seedlings including Douglas-fir, western redcedar, grand fir, ponderosa pine,coastal redwood, port orford cedar, noble fir,  Oregon ash, and a variety of ornamental species. First come, first serve – arrive early for best selection!

Washington County Small Woodlands Association native plant sale: 9:00 am – 3:00 pm, Bales Thriftway in Aloha. A wide variety of container size trees, shrubs, and forbs. See the full list and details by clicking this link.

Weyerhaueser Public Seedling Sale: 8:00 am – noon, Aurora Forest Nursery. About a dozen conifer species of various stock types on sale as well as some hardwoods. Major forest species sold by the bag or in small quantities. All the details are here.

Happy planting!