Brad Withrow-Robinson, Forestry & Natural Resources Extension, Benton, Linn and Polk Counties. Photos Jody Einerson, Benton County Extension.

Backpack sprayers are often used to apply herbicides to control weeds in forestry and conservation work.   It is often helpful to apply two or more chemicals at a time in a “tank mix”.  For example, it is common to apply a foliar herbicide to kill actively growing weeds, along with a soil active herbicide to prevent new weeds from emerging over the following growing season.  Or it may be useful to apply two different herbicides with similar action, but that target different types of weeds (grasses v broadleaf plants).  Be sure to review the post on calibrating a backpack sprayer.

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Brad Withrow-Robinson, Forestry & Natural Resources Extension, Benton, Linn and Polk Counties. Photos by Jody Einerson, Benton County Extension.

In many of our herbicide application situations, the objective is to treat an area, such as a plantation of young trees, at a specific application rate.  By rate, we mean applying a specific amount of a material over a given area (e.g. ounces of product per treated acre).  This is essential when applying soil active herbicides, and also for area treatments (as opposed to targeted spot treatments) with foliar herbicides, particularly if the spray mix will be contacting the seedlings, such as in “over the top” applications. Applying too little material will not give you effective weed control, wasting time and money.  Too much material risks killing seedlings and other desirable plants, or causing other environmental damage.  Figuring out how much spray you are applying so that you can calculate how much herbicide to mix into the spray tank is called calibration.

Once you have calibrated your backpack sprayer, you can apply spray in any number of patterns, and still be putting out an accurate amount of material on a per acre basis.  That means you can accurately treat the entire plantation (broadcast), or discreet parts of that plantation such as row strips or patches around trees with confidence. 

Calibration requires a few simple activities and calculations, in two steps.  Here is a simplified refresher:

Step 1: Find the Application Rate (Gallons/Acre, gpa) you apply

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Brad Withrow-Robinson, Extension & Natural Resources Extension agent for Benton, Linn and Polk Counties.

Spring is the key time to tackle many non-woody weeds.  These non-woody (also called “herbaceous”) plants  include grasses and many common flowering plants including clovers, thistles, oxeye daisy, tansy ragwort and groundsel.  There are many native and also non-native herbaceous plants in the fields and forests of Oregon.

Taking care of unwanted plants/weeds in often an important part of taking care of your land.  Herbaceous weed control if often part of these common objectives:

  • Successfully planting tree and shrub seedlings
  • Reducing fine fuels defending against wildfire
  • Enhancing forest diversity/improving wildlife habitat
  • Easy access and enjoyment of your property
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By Amy Grotta, OSU Foresty & Natural Resources Extension – Columbia, Washington & Yamhill Counties

Holly foliage usually (but not always) has sharp, prickly lobes.

Rid your land of English holly

Fa-la-la-la-la, la-la-la-la

Tis the season to spot holly

Fa-la-la-la-la, la-la-la-la

When all the other leaves are gone

Fa-la-la, la-la-la, la-la-la

Holly’s deep green stands out strong

Fa-la-la-la-la, la-la-la-la

Ok, there’s a good reason I didn’t become a songwriter. The point I want to make, though, is that this is a great time of year to scout your woodland for a common and nefarious invasive plant: English holly. It stays green all year long, so now that herbaceous plants have died back and other shrubs have lost their leaves, it’s easier to spot. Continue reading

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