Brad Withrow-Robinson, Forestry & Natural Resources Extension Agent, Benton, Linn and Polk Counties.

 

Pretty much every landowner I know has a weed issue.

OLYMPUS DIGITAL CAMERASome are fairly short term and narrow, such as controlling common weeds in a new tree planting. Others are much longer term and less defined, such as keeping invasive species at bay in the woodland, or perhaps encouraging  native plants in a meadow or streamside restoration.

There are multiple approaches to weed management, including preventing new weed introductions, mechanical or physical control such as mulching or mowing and the use of herbicides. Most people use a mix of two or more of these approaches, with many including herbicides as one of the methods they use.

Here are some key resources to help you manage your weed issues.

 

ec1563Invasive Weed Identification and Management EC 1563 

It is important to know the enemy, and this is a good place to start, beginning with the 3-page introduction. This publication goes on to describe the identifying characteristics, origin, habitat, ecology and management strategies for selected invasive weeds in the Pacific Northwest. This list is not inclusive of all invasive weeds, but focuses on the most dominant or potentially invasive species that plague us. Check PNW Weed Management Handbook for current herbicide recommendations.

 

The Nature Conservancy’s Weed Control Methods Handbook

A useful resource for many types of landowners, the Weed Control Methods Handbook: Tools & Techniques for Use in Natural Areas provides detailed information about weed control techniques including manual and mechanical methods, grazing, prescribed fire, biological control, and herbicides.  Check PNW Weed Management Handbook for current herbicide recommendations.

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By Brad Withrow-Robinson, Forestry & Natural Resources Extension Agent, Benton, Linn and Polk Counties

 

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photo: VMRC

Last month I spent a morning at OSU attending the annual science meeting of the Vegetation Management Research Cooperative (VMRC). It was well worth the time.

The VMRC’s mission includes conducting applied reforestation research of young plantations from seedling establishment through crown closure and, to promote reforestation success. The VMRC’s research has an emphasis on practical, operational vegetation control, and their research is broadly relevant and readily applied to the needs of family forest landowners, so I do try to keep up on their work.
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By Amy Grotta, OSU Forestry & Natural Resources Extension – Columbia, Washington & Yamhill Counties

Dead tips (upper branch) and stunted growth (lower branch). Photo taken in January 2015, eight months after herbicide was applied.
Dead tips (upper branch) and stunted growth (lower branch). Photo taken in January 2015, eight months after herbicide was applied.

A local landowner contacted me this winter, concerned about his ten acres of young trees and whether they had been damaged by herbicides.  In May 2014, a year after the trees were planted, grass was coming in thick, so he hired a contractor to do a release spray.  We don’t know what the exact spray mixture was, but the landowner thought it may have been a formulation of glyphosate such as Accord.  Glyphosate is known to damage Douglas-fir seedlings (and many other conifers) during the active growing season – the time from when buds begin to swell in spring until resting buds are formed and hardened off in fall.

Affected trees showed several symptoms characteristic of herbicide damage. The least affected trees simply had stunted growth. On many others, the leader and branch tips were droopy and dead. Some seedlings were completely dead. Continue reading

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

Even a wall of blackberries can be tackled
Even a wall of blackberries can be tackled

In recent entries in this series on the basics of herbicide use in weed control, I have reviewed how some foliar herbicides work, and the relationship between the plant’s physiology and the herbicides’ behavior. Now I want to illustrate how that that information translates to what gets done in the woods, looking at controlling blackberries, a frequent target of foliar herbicides.

Blackberries are a problem because they are widely dispersed by birds and start readily from seed and once established, rapidly spread vegetatively by tip rooting, quickly forming daunting patches seemingly too tall and wide to tackle. We’ve all seen these conditions in old pastures, riparian areas and struggling plantations. Continue reading

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