Cull Tree Treatment

[Peter Smallidge]

If you enjoy working in your woodlot and struggle with the undesirable trees that you may not have time and skill to safely fell, this study is designed to find a solution for you.

Many woodland owners have a large number of undesirable trees, or large trees, they would like to kill, yet they lack the skill or time to safely fell these trees. Felling also may not be desirable because of the risk of damage to nearby trees or to avoid the sudden accumulation of felled trees on trails or in the woods. The trees in question are often open-grown trees that have large and coarse crowns.  These trees may have seeded nearby former agricultural fields, but now occupy an excessive amount of growing space and limit the growth of younger, smaller, and potentially merchantable trees. 

You can help test methods to control undesirable pole- and sawtimber-sized trees.

Products, methods, and materials

This study compares herbicide active ingredient impacts on target and non-target unmerchantable pole- and sawtimber-sized trees larger than 4 inches dbh.

Herbicidal control of single trees may be via “hack-n-squirt” (HNS) or “injection” (AKA drill-n-fill, DNF).  HNS requires a hatchet or machete, and sufficient hand and wrist strength to create significant divots in the bark. HNS and DNF are illustrated elsewhere (www.nrs.fs.fed.us/pubs/gtr/gtr_nrs96.pdf). For this project we recommend DNF.

The most popular product for control of a wide range of tree species by HNS or DNF is glyphosate, usually within the product Accord XRT II.  A key attribute of glyphosate is that it is mobile within the tree if applied to the cambium.  Glyphosate is readily available in various formulations from local farm and garden stores, does not leak from the roots or move in the soil, and is considered essentially non-toxic to fish, mammals and birds.  You should wear safety glasses, long sleeves, boots, and nitrile gloves when using glyphosate.

 

List of supplies you should have:

1. Glyphosate concentrate.  You may decide to try an additional product, but check with the project coordinators.
2. Cordless drill and 3/8” bit. 
3. Squirt (spray) bottle. The squirt bottle you use should be chemical grade because on common squirt bottles the seals fail.  We recommend item # 12340 at forestry-suppliers.com or the same product from other vendors such as Home Depot.
4. The dose is 1 ml per 3 inches of tree diameter of a mixture with about 25% active ingredient. If you use Accord XRT II you will dilute that 1:1 (equal parts) in water.  Other products will require a different ratio.  See below for how to apply the correct dose to the tree.
5. A way to mark and number trees. This might be aluminum tags with aluminum nails (for safety) or plastic flagging with a permanent marker.  The marking of the trees must be definitive.

 

List of supplies provided:

1. Tally sheet  download here

 

How do you participate?

Review the list of supplies required for the project. Select one or more treatments, below, to use on your property. In most cases, the experiment will compare Accord XRT II in winter vs. summer. At least 24 - 30 trees of each species will be needed for each comparison.

Contact Kristina Ferrare, CCE Onondaga County at [phone] ext. 231 or email [e-mail] to sign up. A a full technical description is available by searching for “cull tree treatment” at http://CornellForestConnect.ning.com

 

Experimental treatment and field methods:

This project can be started anytime.  Ideally trees will be selected in the summer and preliminary crown conditions can be assigned. It is possible to start in the fall or winter. The need for pre-assessment of crowns can be avoided by randomly assigning trees to the winter or summer group. 

Select trees that you would like to control. Ideally there will be about 24 to 30 of each species.  Stems should be 4 inches diameter (dbh) or larger.  If you are trying to control white pine, consider selecting additional trees that are near the trees you will inject to allow for an assessment of flash from a treated to untreated tree.

Half of trees are assigned to winter and the remainder to a summer DNF injection using the mixture rate and injection protocol described below.  Winter treatments should be applied to all trees at approximately the same time, between December 1 and February 28, presumably when the wood is frozen.  Summer treatments should be applied to all trees at approximately the same time, between June 1 and July 15. A fall treatment is also possible, with an additional 12 to 15 trees and an application between September 1 and November 15. A spring treatment would be applied between April 1 to May 15.

The final assessment for the effects of the herbicide treatment on the trees will use a crown rating index. The crown rating index is adapted from the USDA Forest Service FIA (Forest Inventory and Analysis) field protocol for crown dieback (see pages 22 to 24, here https://www.srs.fs.usda.gov/pubs/gtr/gtr_srs102.pdf).  The index assess the percentage of the crown with foliage and assigns a rating based on the live crown. The process is dichotomous, such that the crown is assessed as “more or less than 50% live.” Then, “more or less than 25% live” (or 75%, as the case may be). Repeating this “more or less” comparison until a crown rating index is determined. The index score is based on the % live crown values one growing season after treatment as shown in following chart.

 

% Live Crown	0	1 – 10%	11 – 25%	26 – 50%	51 – 75%	76 – 90%	>90%
Crown Rating Index	1	2	3	4	5	6	7

 

 

 

Test 1 – compare the crown rating index of the winter versus summer treatments one growing season after the injection. You can add additional seasons by including an additional 12 to 15 trees per season. Only crowns that achieve a rating of 1 or 2 by the following growing season are considered “controlled.”

Test 2 – each week after the summer treatment, assess all trees to identify the date when 90% or more of the foliage is fully brown.  This test does not use the crown rating index, just the extent of browning of the foliage within the growing season of treatment. Record the date a tree reaches this threshold.

Mixture rate - Accord XRT II is mixed 1:1 with water for the concentrated formulation, and applied as 1 ml per 3 inches of stem diameter. This mixture has an active ingredient concentration of approximately 26% glyphosate. Other products will have a different mixing ratio; please check with the project coordinators. Three inches of diameter is about 9 inches of circumference. 

Injection protocol - One milliliter (ml) is a small amount, about the volume of a single garden pea. As another example, one ounce, a small shot glass, has approximately 30 milliliters.   Unless you have a calibrated squirt bottle (most of us don’t), it is easiest to drill and fill a hole of known size.  A hole that is 3/8” in diameter and 1 inch deep will hold 1.8 ml if dilled vertically.  Because you drill into the tree at an angle, the effective volume is reduced.   For this project, drill a hole that is one inch deep into wood (don’t include bark thickness) at approximately a 45^o angle and fill the hole with the herbicide mixture to the interface of wood and bark. Mark the drill bit with tape to produce the correct depth of hole. Drill one hole every 9 inches of circumference. 

The dose per diameter is as follows:

Diameter (inches at dbh)	number of holes, 1 ml per hole
<3 (too small for this study)	1
3 - 6	2
6 – 9	3
9 – 12	4
12 – 15	5
15 – 18	6
18 – 21	7
21 – 24	8
Etc.

Questions about mode of application or methods? Contact Peter Smallidge, Extension Forestry Specialist, at 607-592-3640 or email  [e-mail]

To sign up for the study, contact Kristina Ferrare, CCE Onondaga County at [phone] ext. 231 or email [e-mail] . A full project description is available by searching for “cull tree treatment” at http://CornellForestConnect.ning.com