By Brad Withrow-Robinson, OSU Forestry & Natural Resources Extension – Benton, Linn & Polk Counties

In previous installments of this series on the basics of herbicide use in weed control, I distinguished between foliar and soil active herbicides, describing foliar herbicides as those applied to the leaves or stems of plants to be absorbed and carried throughout the plant to affect control. In the previous post I began discussing foliar herbicides in more detail with an overview of glyphosate.

In this entry I will look at a group of herbicides called “growth regulators” that include some important foliar herbicides and popular weed and brush killers commonly used in forestry, agriculture and habitat restoration. Continue reading

By Brad Withrow-Robinson, OSU Forestry & Natural Resources Extension – Benton, Linn & Polk Counties

In my previous installment of this series on the basics of herbicide use in weed control, I distinguished between foliar and soil active herbicides. In this post I begin discussing foliar herbicides in more detail. Note: The attention given to herbicides in this series does not indicate an advocacy for their use but an acknowledgement that using herbicides presents some unique risks, and that landowners and managers need to know enough about them to make informed decisions on their use.

Foliar herbicides are applied to the leaves or stems of plants to be absorbed and carried throughout the plant to affect control. They are common and widely used to control annual and perennial herbs and also woody shrubs. Continue reading

By Brad Withrow-Robinson, OSU Forestry & Natural Resources Extension – Benton, Linn & Polk Counties

Weed control is a top of mind topic now for many landowners. Following this spring’s strong log market, a lot of folks will be reforesting a harvest unit. Others may be planting a field of Christmas trees, or a swath of trees and shrubs as a restoration project to improve habitat conditions. And it seems everyone is struggling to control one invasive weed or another on the property.

While a number of approaches and strategies (including mowing, pulling and mulching) can and are used in managing weeds, many people will use herbicides as at least part of their approach. This is no surprise given their demonstrated effectiveness and efficiency. But not all users are well-versed in vegetation management, or the science behind it, so some review of herbicides seems to be in order. The attention given to herbicides in this and later articles does not indicate an advocacy for their use but an acknowledgement that using herbicides presents some unique risks, and that landowners and managers need to know enough about them to make informed decisions on their use.

Now, it is important to realize that one need not be a crop scientist to use herbicides. The label gives instructions that ensure the safe and allowable use of an herbicide, so the label needs to be read and followed. But responsible and effective use of herbicides requires some additional understanding about herbicides and how they work, as well as knowledge about the life cycle and other characteristics of both crop and target plant species they will be used with. Let’s begin talking about some basics. Continue reading

A group of Linn County woodland owners on their annual picnic outing, stood in the shade of a 25 year old Douglas-fir plantation on McCully Mountain on a warm afternoon two weeks ago, as Linda Butts talked about the history and growth of the stand.  Planted at 440 T/A, pruned to 8 feet and thinned with a processor three years ago to 170 T/A, it was easy to move around, see the condition of the leave trees, and how they were growing.  The group talked about the thinning, small wood markets (Linda sold thinning as pulp or chip & saw), and of course there was some discussion (unresolved) about whether or not they had taken quite enough trees or not.  But all agreed the stand was looking pretty darn good.

Linda talking about a stand on her family property
Linda talking about a stand on her family property

We also talked a fair bit about getting the stand started 25 yrs ago.  Joining Linda in the discussion were Mike Barsotti and Rod Bardell, retired ODF Service Foresters who had worked with her and other private family forestland owners much of their careers.  What was fun for me was listening to their recollections not just about that particular planting, but also about how much was being learned about planting and establishment in the 70’s and 80’s.  It is always interesting to hear from some of the pioneers. Continue reading

By David Shaw, OSU Extension Forest Health Specialist

western oak looper
Top left: western oak looper caterpillar; Top right: oak leaf eaten by looper; Bottom left: affected tree appears dead; Bottom right: caterpillars aggregating on a fence post. Photos: Dave Shaw

Insects of Oregon white oak are causing some damage this summer, and you may be seeing trees that look completely brown or have scattered dead branches (distinct brown foliage clumps all through the crown).  There are two different issues that have emerged around the Valley this summer:  whole tree defoliation/leaf eating by the western oak looper (Lamdina fiscellaria somniaria); and scattered branch death caused by the combination of a twig gall wasp (Bassettia ligni) and the western grey squirrel.

The western oak looper (a type of inchworm) is a flashy defoliator that is a native in the Willamette Valley.  The caterpillars are messy feeders, hang by silken threads, and leave browned mostly consumed leaves all over the tree, giving the tree the appearance of being dead.  But the oak trees usually come back the next year.  Historically, the outbreaks have been of short duration in any single area (typically one or two years) and the oak trees rarely suffer long term damage even though the defoliation may be spectacular.  However, when conifers such as Douglas-fir are intermingled with affected oaks, they can also be defoliated in an outbreak and impacts to the Douglas-fir may be more severe. Continue reading

Fire Season is now or soon will be in effect in much of the Tree Topics reading area, as declared by the State Forester according to regional fire conditions. So I got online to see what’s been declared. I went over to the ODF Wildfire website and clicked on Forest Restrictions and Closures  section. There you can find links to an overview of the Industrial Fire Precaution Level (IFPL), closures and other information about fire regulations and restrictions. Continue reading

Ellie's log_bookDo you struggle with ways to engage your child, grandchild, or a young scientist friend with our local forest lands? I would like to suggest a new book, Ellie’s Log, to nurture your young scientist, and to help you both explore the mysteries in our collective backyard of Oregon’s forests. Ellie’s Log is part fictional story, part forest ecology lesson, and part field journal all set in a mature Douglas-fir forest in Oregon. Continue reading

Last week, we kicked off our Master Woodland Manager training in northwest Oregon. Over the next six months the class will explore many aspects of small woodlands management and the trainees will come away with a better understanding of their own lands as well as a foundation from which to assist others.

We started out with a field tour where we investigated the environmental factors that influence forest growth on a given site. In particular, we wanted to see how variations in climate, topography and soil shape species composition, forest productivity, and management opportunities.

We went to five different sites, at various elevations and topographic positions from the uplands to the Valley floor. Despite the sites all being within a four-mile radius, we saw striking differences in the vegetation. The uppermost site supported a fast-growing stand of Douglas-fir and red alder. Further along, we came upon a rocky, south-facing site dominated by madrone and some not-as-fast-growing Douglas-fir; but this was just a few hundred yards from another site where the madrone were gone. Calculating the site index revealed that the Douglas-fir here were growing faster.

As we traveled down the watershed, the steep slopes along an upland creek supported alder and western redcedar. But on the flats further down the watershed, at our last stop on the Valley floor, the dominant species were Oregon white oak, Oregon ash, and valley ponderosa pine; the Douglas-fir at this last stop looked like they had caught a bad case of the crud.

Prior to the field tour, we spent some time learning how to find information about soils. The Web Soil Survey is a really handy tool for identifying soil types and learning about their properties. Using the Web Soil Survey, we mapped out our field sites and found some possible clues to our site differences. According to our soils map, the madrone were growing on a gravelly Saum soil, whereas the taller firs down the road were on the more productive Jory soil.

soil map

A recently formed gully at the latter site gave us the opportunity to see the soil profile which revealed a deep silty clay loam.

Jory soil profile

Jory phone screenRecently I’ve discovered SoilWeb, which has become one of my favorite natural resources-related mobile apps, available for both the iPhone and Android. Using your phone’s GPS capability, SoilWeb accesses the soil data from the Web Soil Survey for the soil right underneath your feet. That is, assuming A) that you are in a place where you can get a phone signal and B) that the soil maps accurately reflect the soil on your site. As we learned on our field trip, soil types as mapped often contain unmapped pockets of other soils.  The SoilWeb app doesn’t give you everything you can find on Web Soil Survey, but you can quickly ascertain the soil texture as well as the expected depth, drainage, and other important features.

The takeaway from our tour was that what’s growing on your forest can be a clue to your site’s underlying environmental influences, and vice-versa. The growing number of applications such as SoilWeb makes it easier to be a site “sleuth”, finding those clues and piecing together the puzzle.

Amy Grotta

drought stressThe phone has been ringing off the hook lately with calls from people describing sick and dying Douglas-fir and other conifer trees. The trees are of a wide range of ages and in many environments and settings, although most calls have been coming from within the valley margin and have to do with young trees.

So far, the answer is generally: “It is drought stress”.  Huh, in May? Well it has been a dry winter and spring, … but that is not the issue.

My best explanation is that we had a pretty hard end of summer last year. Remember that? NO rain until mid-October then, Boom, it was winter. By then, many trees had started running out of water, killing tops or branches, and leaving leaders and branches susceptible to attack by various opportunistic pests.

We started seeing a few classic signs of drought stress (tops dying and branches “flaring out”) at the very end of the season last year, but late enough that many did not have time to show up before the weather turned. Injuries had occurred, so it was just a matter of time before they expressed themselves, which is happening now. The recent hot weather seems to have made it more sudden and dramatic.

This happens from time to time. Here are two good articles a few years back by the ODF Forest Health team explaining Dead tops and Branches (with Good pictures), and about Drought and Mortality.

It is important to keep in mind that the Willamette Valley can be a challenging climate for trees. Many of our soils in the valley are poorly drained, which is hard on most of our conifers, and other soils are fairly shallow and cannot hold much water. Also our summers are hotter and drier than in the mountains. Heat and drought stress can kill trees outright, or more often just put the trees under stress, which can then lead to pest problems (as explained in the two publications above). From what I am seeing and hearing, the major cause of the problem now seems to be drought stress. Insect or diseases which able to take advantage of a stressed tree’s condition may sometimes be involved, but they are generally not the cause of the problems.

Finally, weather can be more stressful when trees are overcrowded, so thinning stands to keep trees vigorous with adequate growing space may be helpful in the long term. Right now, we just have to wait it out, and hope we get some serious rain this year, or we will see this problem intensify.

We all better get out there and wash the car…..

Brad Withrow-Robinson

In response to last week’s post on the value of dead wood in the forest, I received this e-mail from a landowner:

“We’ve never left much on the ground in the way of dead wood…not during logging, but wind damaged, etc.  Our thought has always been that these rotting logs increase the insects in the forest, both good and bad. Is this a valid concern and if so, where is the balance between bugs and wildlife?”

He raises a point worth exploring. While calling an insect “good” or “bad” is a matter of perspective, for the purposes of this discussion let’s assume that “bad” insects are those that cause economic or environmental damage, and “good” insects are those that don’t. The vast majority of insects that inhabit western Oregon forests fall into the “good” category…with a few notable exceptions.

One of these “bad” bugs that the e-mailer might have in mind is the Douglas-fir beetle. This time of year, the adult beetles are flying around in search of Douglas-fir trees where they lay their eggs underneath the bark. Their favorite targets are large diameter, freshly downed logs—or standing trees that are weakened from another cause (root disease, soil compaction, etc.). Through the summer and winter, the eggs hatch and the larvae grow as they tunnel around under the bark (this activity is what kills the tree). The following spring, they have become adult beetles, and they fly away in search of new homes. If they can’t find another weak tree or fresh log, they will go after a healthy tree.

Douglas-fir beetle (Dendroctonus pseudotsugae ) on Douglas-fir (Pseudotsuga menziesii ) - 1587008
reddish bark dust in bark crevices is a sign of the Douglas-fir beetle (Photo: Elizabeth Willhite,

Healthy trees can withstand a low-level Douglas-fir beetle attack, and in normal circumstances there are rarely enough beetles around to cause concern. The problem arises when the beetle population builds up and lots of them infest a healthy tree at once. When does that happen? In situations where there is a lot of freshly downed or damaged wood on the ground for them to target initially – like after a winter windstorm.

Here’s a true story for illustration.

In fall 2009, a landowner in the Coast Range was hit hard by beetle kill to his otherwise healthy, 100+ year old forest. Why? Here’s how we think this may have played out.

  • The stand is adjacent to a sawmill.
  • The big windstorm of December 2007 created lots of blowdown along the coast, though this particular stand was too far inland to be damaged.
  • Some of the coastal blowdown was not salvaged until summer 2008…too late, because Douglas-fir beetles had already found them during the spring.
  • The salvaged logs were brought to the mill, along with the beetle larvae living under the bark.
  • Then, in late 2008 the recession hit and the mill curtailed operations. The logs sat in the deck…and the beetles matured.
  • In spring 2009, they emerged and flew off to the neighboring stand, where they attacked the healthy, mature trees.

It was a sad situation, especially since the landowner had to cut more trees to avert further beetle damage, and in a poor market.

So, back to the e-mailer’s question: does retaining snags and downed wood for wildlife create a forest health risk? The take-home messages are these:

  • Most insects are not forest health risks.
  • In western Oregon, the Douglas-fir beetle (the “baddest” dead wood-inhabiting insect) only thrives in FRESHLY dead or downed trees. Once the snag or downed wood has been dead for more than a year, it is no longer a target. Instead, it will become inhabited by the dozens of “good” bugs that feed wildlife.
  • There needs a LOT of this fresh down wood to pose a forest health risk – like after a storm. According to Oregon Department of Forestry, a good rule of thumb is that fewer than 3 FRESH down logs/acre does not present a hazard.

After a windstorm or other stand-damaging event, yes, prompt salvage is important in order to prevent a beetle infestation. But, when scattered trees gradually die in a stand from other causes, it is hard to imagine when this would create a risky situation with respect to bark beetles. And during harvest activities, you can be strategic about how much dead wood is left behind, and in what conditions.

We appreciate it when readers respond to our blog posts. We like your e-mails, but you can also respond by commenting directly on the blog, where other readers can contribute to the conversation.

Amy Grotta