Larry R. Nelson
Extension Forester and Associate Professor
Department of Forest Resources
Clemson University
Clemson, SC 29634-1003

Rick L. Cantrell
Senior Director, Forest Policy and Sustainable Agriculture
American Forest & Paper Association
1111 19th Street, NW Suite 800
Washington, DC 20036
(Formerly with the University of Tennessee Agricultural Extension Service)

Note: Chemicals contained herein are labeled for forestry uses based on the most up-to-date information available to the authors. Use of trade names is solely for identification. No endorsement of the products named is implied by the Clemson University Cooperative Extension Service nor is any discrimination intended by the exclusion of products or manufacturers not named.


Table of Contents

INTRODUCTION

USING THIS GUIDE FOR HERBICIDE PRESCRIPTIONS

FOREST HERBICIDE PRESCRIPTION FLOWCHART (Figure 1)

SIGNIFICANCE OF INPUT TOPICS USED FOR PRESCRIPTIONS

Crop Species
Dominant Weed Species
Other Factors Affecting Efficacy
Environmental Concerns
Other Critical Factors
Factors Affecting Application Methods

ARRANGEMENT OF TECHNICAL INFORMATION

SITE PREPARATION

Registered Herbicides (Table 1)
Products x Crop Trees (Table 2)
Species Susceptibility (Table 3)
Herbicide Characteristics
Application Methods (Table 4)
Recommended Treatments (Table 5)

RELEASE

Registered Herbicides (Table 6)
Products x Crop Tree (Table 7)
Species Susceptibility (Table 8)
Herbicide Characteristics
Application Methods (Table 9)
Recommended Treatments (Table 10)

HERBACEOUS WEED CONTROL

Registered Herbicides (Table 11)
Products x Crop Trees (Table 12)
Species Susceptibility (Table 13)
Herbicide Characteristics
Application Methods
Recommended Treatments (Table 14)

Selected References and Literature Cited

Appendix A - Herbicide Application Records Sheet ...................................pdf format

Appendix B - Common and Scientific Names of Weed and Crop Species Included in This Manual


Appendix C - Herbicide Terminology

Appendix D - Chemical Companies


 

 

 

Introduction

Numerous herbicides are registered for forestry use in the Southern United States. These are described in detail on product labels and technical brochures. In addition, forest herbicide use has been systematically summarized in various guides. However, from a practical standpoint, most sources do not present information required to effectively prescribe herbicide treatments. The Chemical Expert System for Silviculture (CHESS) developed at Virginia Polytechnic Institute and State University is a very effective and valuable prescription writing tool, but requires an adequate computer, software and a capable operator.1 A need still exists for a concise, written reference of herbicide prescription information with general accessibility for both the field and office.

The objective of this work is to describe important variables influencing forestry herbicide prescriptions and the characteristics of individual products that may interact with those variables. The information is arranged so as to clarify conditions under which particular products are most effective, and to help eliminate the misuse of products in situations where they clearly do not fit.

This manual is intended to serve as a guide for the novice practitioner involved with occasional forest herbicide use and as a quick reference for more experienced users. For simplicity, we focused upon major herbicides used for forest site preparation, conifer release, and herbaceous weed control.


Alternative Vegetation Management Practices

Before proceeding, a few comments are appropriate regarding alternative vegetation management methods. Vegetation control should be conducted to fit within and enhance the overall objectives of a sound forest management plan. An effective land manager should determine whether chemical control will meet these objectives and at a similar or lower cost than other control methods. Currently, alternatives are available primarily for site preparation (mechanical methods and controlled burning) and timber stand improvement (controlled burning), while pine release and herbaceous weed control are accomplished almost exclusively with herbicides.

The suitability and cost effectiveness of herbicides compared to mechanical site preparation can be affected by a number of factors. Mechanical site preparation has traditionally been used extensively because it offers a dependable method of clearing a site for either machine or hand planting. However, use can be restricted somewhat by wet weather, poor drainage or extremes in topography. Other problems include negative impacts on erodible or fragile soils and the potential for abundant hardwood sprout development.

Herbicide treatment alone or in conjunction with controlled burning has limited impact on most soils and is not restricted by terrain. Herbicides will control hardwood resprouting when used correctly and are generally less expensive than mechanical treatments. However, chemical site preparation is often restricted to sites that are to be hand planted and is ineffective on sites with abundant herbicide-resistant species. Herbicide use is sometimes restricted by environmental concerns, and requires technical training by the user.

Many of the above features are easily assessed, but quantitative yield data relating vegetation control to increased crop tree growth and cost effectiveness is not readily available. An acceptable level of vegetation control is generally an arbitrary condition based on perceptions of the practicing forester. Nonetheless, making a reasonable decision as to whether the use of herbicides is appropriate requires an understanding of their effects and limitations.

1Chemical Expert System for Silviculture (CHESS) can be obtained by writing to Virginia Tech, School of Forestry, Blacksburg, VA 24061.

Using This Guide for Herbicide Prescriptions

The herbicide prescription process involves matching a suitable herbicide treatment to a specific silvicultural objective. It can be confusing in that several products may be registered for a general purpose with each exhibiting desirable or undesirable traits for specific site conditions. Although it may not always be possible (or necessary) to select a single “best” treatment for a given site, selection(s) should still be based on a series of logical actions and decisions.

Three functions of this guide are to:

(1) direct the user through a logical sequence of considerations required for the prescription process;

(2) provide an understanding of these considerations;

(3) provide convenient access to pertinent technical information about specific herbicides.


Arrangement of Technical Information

The prescription process, presented as Figure 1, consists of a flow chart of the hierarchy of considerations necessary for herbicide prescriptions. The chart directs a series of actions in response to various input topics in the order that they normally occur when formulating a prescription. In order to use the flow chart effectively, the user must understand the significance of each input topic. These are described immediately following the chart under the heading “Significance of Input Topic Used for Prescriptions.”

Technical information on registered herbicides can be sequentially accessed from Figure 1. Note that in the figure, colored blocks labeled “Site Preparation,” “Release,” and “Herbaceous Weed Control” correspond to major sections of the manual. Refer to the table of contents for easy access to each section. Technical information within each section is formatted to match shaded blocks in the remainder of the flow chart. These include:

(1) a table of registered products;

(2) a table of registered products and crop trees for which they are labeled;

(3) a table of species susceptibility;

(4) herbicide descriptions;

(5) a table of application methods.

A sixth table is included at the end of each section as a reference source. This table lists treatments that are commonly recommended or used for specific conditions. The treatments cover many of the site conditions encountered in the southeast but are not all-inclusive. Information in the manual and product labels should be read carefully before buying, applying or disposing of any herbicide.

The user of this guide must understand that it was not designed to make decisions, but to provide order and access to information required for those decisions. The flow chart directs the user to registered products, crop species for which they can be used, and weed species on which they are effective. Beyond this point, distinguishing features necessary for prescriptions must be obtained through careful reading of individual product descriptions.

Significance of Input Topics Used for Prescriptions

Crop Species
It is unlawful to use herbicides or other pesticides on crop species other than those specified on the label. The pesticide label is a legally binding document. Violation of the label can result in damage to crop trees and/or litigation. Consult tables 2, 6, and 10 for product specific information.

Dominant Weed Species
Before prescribing any herbicide, a survey must be conducted to identify dominant weed species on a site. A stand (woody or herbaceous) will generally be comprised of three to four major species. An herbicide should be considered acceptable as long as resistant (relatively unaffected) species are only a minor component.

Species susceptibility is addressed in tables 3, 7, and 11 for site preparation, pine release and herbaceous weed control. The tables categorize weeds as either highly susceptible or “resistant.” This approach is somewhat simplistic. However, data necessary to accurately specify intermediate gradients of control are unavailable. We therefore chose to emphasize resistant species (in bold type) in order for the reader of this guide to avoid using herbicide products where they clearly will not work.

Other Factors Affecting Efficacy
Other factors in addition to species that affect herbicide efficacy include soil type, application timing, and weather. Implications are discussed below and specific features of each product are outlined in the same order within the product description sections of the guide.


Soils

Soil-active herbicides may be strongly impacted by soil texture, percent organic matter, and internal drainage. Texture and organic matter determine the adsorptive capacity of a soil. Microscopic colloids (clay and organic), have a large surface area in proportion to volume and tend to adsorb herbicides in proportion to their content. Thus, fine textured soils (clays) or organic soils have a higher tendency to bind herbicides, making them less available for uptake by root systems of target vegetation. Generally, product labels provide a range of application rates for various soil types. Frequently, higher rates of an herbicide are required on soils high in clay or organic content. On the other-hand, for pine release or herbaceous weed control in young stands, care must be exercised so that injury to the crop trees does not result from over-application on sandy or coarse textured soils. A user should read the label carefully, know the soil type, and make sure that applications are conducted according to specifications.

Effects of internal drainage on herbicide activity have not been widely studied. However, it is known that certain products do not work well on poorly drained sites.


Timing

Application timing is critical with several herbicides. Soil-active herbicides are generally applied in the spring to early summer when rainfall required for activation is likely to occur. Similarly, foliar products are applied after full foliar development in the spring. However, there are exceptions. A few products can be applied throughout the growing season or in early to mid-fall.


Weather Conditions

Local weather conditions should be considered when selecting either soil-active or foliar products. Soil-active products require rainfall to activate and move the herbicide into the soil profile. Too little rainfall can result in low herbicidal activity, and too much can wash herbicides off-site or deep into the soil profile, below the active rooting zone of the target species. Likewise, foliar products may be washed from leaf surfaces when applied immediately before rainfall. Minimum time intervals between application and rainfall are recommended for some products.

It is speculated that dry weather during the previous fall and current spring can stress vegetation and increase herbicide susceptibility. This may increase the risk of damaging crop trees during pine release or herbaceous weed control.

Applications of certain translocated foliar products appear to be most effective when plants are at peak physiological activity. Lower herbicidal activity might be expected from applications conducted during extremely cool, wet springs.

Environmental Concerns
Environmental concerns generally involve human safety aspects and the potential economic and ecological impacts that result from misapplication or movement of product beyond the target site or vegetation. Crop species such as cotton, soybeans, grapes, tomatoes, and tobacco are very sensitive to certain products and can be damaged when exposed to spray drift or volatilized chemical. Similarly, movement of soil-applied products with surface flow following rainfall can be detrimental to off-site vegetation and/or contaminate groundwater, streams, ponds, etc. Significant environmental features such as toxicity, volatility, and behavior in soils are included in product descriptions.

Other Critical Factors
Other critical factors feature miscellaneous product-specific information highlighting positive and negative traits as well as important warnings. These are included under the last heading in the product descriptions and should be read carefully.

Factors Affecting Application Method
The practicality of a herbicide prescription depends on both a high level of efficacy under a given set of conditions, and on availability of a suitable application method. Application methods registered for specific herbicides are listed in Tables 4 and 9, and on page 48. For practical reasons, only those methods listed on product labels are included. Additional methods may be legal as long as the label does not prohibit their use. However, we advise a potential user to check with either a representative of the product manufacturer or with the Cooperative Extension Service before using methods not included on the label. Some of the factors affecting choice of application method are discussed below.


Acreage

Tract size can influence choice of application method, cost of application, and potential for contracting the work to a commercial applicator. Applicators using aircraft or heavy equipment have a general desire to work large tracts of land because of the fixed costs associated with moving and setting up equipment. Their cost per acre declines with the number of acres treated and they are often unwilling to treat small tracts (50 acres or less) unless located near a larger operation or grouping of smaller tracts. Fortunately commercial applicators that use ground crews with backpack sprayers or other hand-held devices are available in many areas. They are less affected by tract size and will often work smaller tracts at a reasonable cost.


Topography

Rough terrain or inaccessibility can preclude the use of ground crews or equipment. Aerial applications are often the only practical means of treating such lands.


Stand Density and Structure

Ground applications of herbicides require a site that machinery or ground crews can move across with reasonable ease. When applying foliar or soil-active products at a rate per unit area, machinery such as rubber tired skidders or track vehicles must be capable of moving at a uniform speed. Such applications are practical only on sites with few hardwoods left after harvest.

Backpack applications for site preparation or pine release are affected by stand density and height. Stands with a high density of hardwoods and other understory growth are difficult to traverse and are costly in terms of treatment time. Application is also difficult if target stems are greater than five to six feet in height. Controlled burning can sometimes open the stand and kill stems to the groundline, where after resprouting they can be treated with relative ease.

Aerial applications are affected by stand structure. Lower components of multistory canopies can be difficult to cover with foliar treatments due to shielding from taller trees. Partial solutions to this problem include increasing total gallons of spray per acre, using solid formulations or products with both foliar and soil activity.


Sensitive Areas

The location of sensitive areas such as crops, endangered species, water sources, wetlands, grazing lands, dwellings and public areas can have a direct effect on application method as well as herbicide selection. Movement of herbicide from the target area to any of these is a label violation subject to litigation. This can occur through drift of fine spray particles during application, movement of volatilized product during or after application, and movement of products in surface water. Potential problems can be avoided by using proper equipment and selecting products that do not volatilize or move with surface water.

Aerial applications should be used cautiously and avoided completely in high risk areas. Applications should be conducted under ideal weather conditions (wind speed less than 5 mph, and temperatures lower than 85 degrees Fahrenheit). Nozzles that deliver herbicides in large droplet sizes should be used in combination with drift control agents. Also, the presence of a helicopter or fixed wing aircraft near any sensitive area is likely to draw considerable attention to a spray operation regardless of risks. Advance notification of the operation to the local population can be used to determine any objections. In such cases alternative application methods or mechanical treatments may be advisable. Foliar ground applications are generally less prone to drift than aerial. However, similar precautions should be used. At times it may be advisable to treat buffer areas surrounding a tract by hand or other ground methods and broadcast treat only the interior portion of the site.

Soil-active products in liquid or granular form can be applied from the ground with little risk of drift. Products that will move with surface water should not be used on sites that drain into water supplies or any other sensitive area.


Wildlife Habitat

Land managers should be aware of possible impacts of herbicides on wildlife. Wildlife is often featured as a forest management objective, and certain animal as well as plant species are protected under the Endangered Species Act.

Normally, impacts on wildlife due to direct exposure to forestry herbicides are negligible. Forestry herbicides are not highly toxic to animals, are applied at relatively low rates, and do not persist for long periods in the environment. The reader is referred to Cantrell and Hopper (1989) for a more detailed discussion of this topic.

Herbicides impact wildlife primarily by affecting habitat. This impact may be positive or negative. The degree of habitat modification depends upon the component of vegetation at which the treatment is directed and the type of application. Some herbicides primarily control woody species, some control herbaceous grasses and forbs, while others can temporarily eliminate nearly all vegetation on a site when broadcast at highest labeled rates. Even in the most extreme case the effects are temporary. Sites treated with broadcast applications generally revegetate within a year after treatment. The land manager should select treatments based on his objectives. Herbicide applications can be manipulated to favor wildlife. Selective application methods can be used to create habitat diversity and enhance wildlife food and cover. The reader is referred to Hurst (1989, 1988a, 1988b) and Witkowski, et al, (1988) for additional information.

 

Site

Preparation

 

Site Preparation

Effective site preparation prior to planting pines will strongly impact the overall species composition of the developing stand. Herbicides can be used to implement a wide range of site preparation intensities. Excellent vegetation control can be achieved with broadcast applications at labeled rates of several broad-spectrum products. Lower rates and/or selective ground application methods are available for less intensive vegetation control. The user should base product, rate, and application selections on management objectives. The following section of this manual will help with the technical aspects of the decision process.


Table 1
Herbicides Registered for Forest Site Preparation
in the Southern United States (1989)
.

Common Name
Trade Name
Manufacturer
Dicamba Vanquish Syngenta
Glyphosate Accord SP, OneStep1 Dow Agrosciences
Hexazinone Pronone 25G Pro-Serve
Hexazinone Pronone 10G Pro-Serve
Hexazinone Power Pellets Pro-Serve
Hexazinone Velpar L DuPont
Hexazinone Velpar ULW2 DuPont
Imazapyr Arsenal Applicators Concentrate, Chopper, OneStep BASF
Metsulfuron Escort DuPont
Picloram Tordon K Dow AgroSciences
Picloram + 2,4-D Tordon 101 Mixture, Tordon 101 R, Tordon RTU3 Dow AgroSciences
Triclopyr (amine) Garlon 3A Dow AgroSciences
Triclopyr (ester) Garlon 4 Dow AgroSciences

1Velpar ULW is available only as a package deal in which the herbicide dealer prescribes the rate, contracts the application, evaluates results and retreats if necessary.

2OneStep is a prepackaged mixture of 8.36% imazapyr and 22.13% glyphosate.

3For injection only.


 


Table
2
Herbicide products registered for forestry site preparation,
crop tree species for which they are labeled, and recommended
time intervals between application and planting.

Product Name
Crop Tree Species
Time Interval1
Vanquish conifers not specified
Accord SP conifers none
Escort loblolly, slash not specified
Pronone 25G loblolly, longleaf, slash, shortleaf, Virginia pine not specified
Pronone 10G loblolly, longleaf, slash, shortleaf, Virginia pine not specified
Power Pellets conifers not specified
Velpar L loblolly, longleaf, slash, shortleaf, Virginia pine not specified
Velpar ULW loblolly, longleaf, slash, shortleaf, Virginia pine not specified
Arsenal Applicators Concentrate loblolly, Virginia, slash pine not specified
OneStep loblolly, longleaf, shortleaf, slash, white pine not specified
Chopper loblolly, longleaf, shortleaf, Virginia, slash, white pine not specified
Tordon K conifers 6 months
Tordon 101 Mixture conifers 6 months
Garlon 3A conifers 1-2 months2
Garlon 4 conifers 1-2 months2

1Time intervals between application and planting are not specified on several labels. Applications early in the growing season generally provide for a sufficient time interval for dissipation of the product prior to planting the following planting season.

2The time interval is rate dependent; see label for details.


Table 3
Susceptibility of woody species to various site preparation herbicides.1

Herbicide
Common Name
Highly Susceptible2
"Resistant"2
Dicamba pines, white oak, blackgum, sumac red maple, ash, hickory, elm, dogwood, persimmon
Glyphosate broad spectrum control of hardwoods and pines red maple, ash, hickory, dogwood
Hexazinone broad spectrum control of hardwoods and white pine yellow-poplar, eastern redcedar, sassafras, blackgum, pines, hollies, American beautyberry
Imazapyr broad spectrum control of hardwoods elm, locust, redbud, pine, buckeye, waxmyrtle
Metsulfuron3 black cherry, black locust, elm, dogwood, maple and ash not specified to date
Picloram broad spectrum control of hardwoods and pines ash, eastern redcedar
Picloram + 2,4-D broad spectrum control of hardwoods and pines ash, eastern redcedar
Triclopyr (amine) broad spectrum control of hardwoods and pines black cherry, eastern redcedar
Triclopyr (ester) broad spectrum control of hardwoods and pines black cherry, eastern redcedar

1Information in this table is based on published data and on personal communication with various vegetation management specialists. As with all “susceptibility” tables, caution must be exercised when using this information. A concentrated effort was made to only include weed and crop species that are consistently controlled by, or consistently “escape” a particular herbicide.

2Highly susceptible indicates that the weed or crop species is very sensitive to the herbicide indicated at labeled rates; resistant indicates that the weed or crop species will be relatively unaffected by the herbicide indicated at labeled rates.

3Escort (metsulfuron) is labeled as a tank mix with either Arsenal Applicators Concentrate (imazapyr) or Accord (glyphosate) in order to improve control of species listed as “highly resistant.” Escort by itself is not recommended for broad-spectrum woody brush control.


Herbicide

Characteristics

Affecting Prescriptions

 

DICAMBA (Vanquish)
Factors Affecting Activity
Activity Foliar and soil.
Soils Dicamba is quite mobile in soil. Concentration and location of dicamba in soil is determined by application rate, total precipitation, and frequency.
Timing Apply in spring to early summer after full foliar development of target species.
Weather

Heavy rainfall can move dicamba off site or deep into the soil profile, reducing activity.

Environmental Concerns
Toxicity Product has a low order of toxicity to fish and wildlife.
Volatility Dicamba is relatively nonvolatile; however, precautions should be taken to avoid drift since crops such as cotton, beans, grapes, tobacco and tomatoes are extremely sensitive.
Precautions Utility may be somewhat restricted by potential movement off-site and extreme sensitivity of certain crops. See precautions on label.
Other Critical Factors
* Product is relatively inexpensive but controls a fairly narrow range of hardwood species.
ALWAYS READ THE PRODUCT LABEL AND MATERIAL SAFETY DATA SHEETS BEFORE MAKING PRESCRIPTIONS.

 

GLYPHOSATE (Accord SP)
Factors Affecting Activity
Activity Foliar
Soils Product is not soil-active. Foliar activity is unaffected by soil texture and organic matter. Product is adsorbed tightly to soil particles. It is relatively immobile and nonpersistent.
Timing Product can be applied throughout the growing season but is most effective from late summer through fall, but before significant leaf coloring and drop.
Weather

Rainfall within 2 to 6 hours after treatment may wash herbicide from foliage and reduce efficacy.

Environmental Concerns
Toxicity Very low. Product can cause severe eye irritation by direct exposure.
Volatility Negligible
* Product has desirable traits regarding environmental effects. Glyphosate has low toxicity, is bound tightly to soils, and is not persistent.
Other Critical Factors
* Glyphosate is effective on a variety of hardwood species found on upland and mountainous sites.
* Foliar activity requires thorough coverage of target vegetation. Some shielding may result from broadcast applications over multistory canopies.
ALWAYS READ THE PRODUCT LABEL AND MATERIAL SAFETY DATA SHEETS BEFORE MAKING PRESCRIPTIONS.

 

HEXAZINONE

(Velpar L, Velpar ULW, Pronone SG and 10G Power Pellets)

Factors Affecting Activity
Activity Soil and some contact foliar activity.
Soils

Products are very cost effective on coarse or light-textured soils with predominantly oak species. Hexazinone is mobile in soil. Persistence studies indicate that the half-life in soil ranges from 1 to 6 months depending on soil texture, moisture, temperature, etc. Activity is low or inconsistent on poorly drained soils.

Timing Apply early spring to early summer when rainfall necessary for activation is available. In freshly harvested areas with numerous stumps, a delay of one growing season to allow stump sprouts to develop will enhance control.
Weather Rainfall is necessary for activation.
Environmental Concerns
Volatility Negligible for liquid formulations. None for solid formulations.
Toxicity Very low. Velpar L can cause severe eye irritation by direct exposure.
* Products have a low toxicity rating for fish and wildlife.
Precautions Mobility with soil water can be a problem on certain sites. Attention should be paid to soil type and slope when considering possible movement to sensitive areas or into water table or agricultural and domestic use water. Do not apply within the root zone of desirable hardwoods.
Other Critical Factors
* Broadcast applications control many understory grasses and forbs, providing fuel for control burning.
* Residual weed control from broadcast application may promote early pine growth.
* Treatments on clay soils can be expensive due to high application rates required for effectiveness.
* Efficacy will be inconsistent during drought years.
ALWAYS READ THE PRODUCT LABEL AND MATERIAL SAFETY DATA SHEETS BEFORE MAKING PRESCRIPTIONS.

 

METSULFURON (Escort)
Factors Affecting Activity
Activity Primarily soil-active with some foliar activity.
Soils No data.
Timing Foliar applications should be made after full foliar development in the spring until fall colors develop late in the season.
Weather

Effectiveness may be reduced if rainfall occurs within 24 hours after application.

Environmental Concerns
Volatility Negligible.
Toxicity Low oral and dermal toxicity.
Other Critical Factors
* Use of a non-ionic surfactant is recommended for applications of Escort alone.
ALWAYS READ THE PRODUCT LABEL AND MATERIAL SAFETY DATA SHEETS BEFORE MAKING PRESCRIPTIONS.

 

IMAZAPYR (Arsenal Applicators Concentrate, Chopper, OneStep)

Factors Affecting Activity
Activity Both foliar and soil activity.
Soils

Imazapyr has both soil and foliar activity and is not strongly affected by soil texture and organic matter content. Arsenal appears to be very stable in soil. It does not move far laterally or vertically. The active ingredient is fairly persistent.

Timing Product can be applied at any time during the growing season from full foliar development in the spring until fall colors develop late in the season. Since activity is slow, early season application should be conducted when a controlled burn is planned for late July or August.
Weather No significant effects have been reported.
Environmental Concerns
Volatility Negligible.
Toxicity Arsenal has a very low order of toxicity to fish and wildlife.
* Low toxicity to fish and wildlife, stability in the soil, and nonvolatility are positive attributes.
Precautions Spraying directly up to adjacent property lines may result in damage or mortality to trees and shrubs that receive chemical on a portion of the crown or on soil within the root zone.
Other Critical Factors
* Product controls a wide range of both woody and herbaceous species.
* Control of understory species promotes controlled burning and residual control may enhance early pine growth.
ALWAYS READ THE PRODUCT LABEL AND MATERIAL SAFETY DATA SHEETS BEFORE MAKING PRESCRIPTIONS.

 

PICLORAM (Tordon K)
PICLORAM + 2,4-d (Tordon 101M, 101R, RTU)

Factors Affecting Activity
Activity Both foliar and soil activity
Soils Products are not strongly affected by soil texture and organic content. Picloram is adsorbed to organic matter and clay particles but water soluble amine formulations will leach in light textured soils low in organic matter. It is broken down slowly by microbial activity and can be quite persistent depending upon geographic location, climatic conditions, and application rate.
Timing Foliar treatment is most effective when applied after full foliar development in the spring, but before the onset of hot dry summer weather. Injection with Tordon 101 R or RTU can be conducted throughout the year, except during heavy sap flow in the spring.
Weather

Applications immediately after cool wet spring weather may result in reduced efficacy.

Environmental Concerns
Toxicity Picloram has a low order of toxicity to fish and wildlife and breaks down rapidly in clear, flowing water.
Volatility Negligible
Precautions Long-term persistence may be undesirable, particularly in areas where accumulation in agricultural and domestic use water is possible.

Spraying directly up to adjacent property lines may result in damage or mortality to trees and shrubs that receive chemical on a portion of the crown or on soil within the root zone.

Many agricultural crops (soybeans, tobacco, cotton, tomatoes, grapes, etc.) are very sensitive to picloram. Do not use if spray drift or contamination of irrigation water is likely.

Other Critical Factors
* Certain products containing picloram are classified as restricted use pesticides. The applicator must be certified in order to use the product. Consult the product label before using.
* Product controls a wide range of both woody and broadleaf herbaceous species.
* Control of understory species promotes controlled burning although many grasses and certain forbs are resistant.
ALWAYS READ THE PRODUCT LABEL AND MATERIAL SAFETY DATA SHEETS BEFORE MAKING PRESCRIPTIONS.

 

TRICLOPYR (Garlon 3A, Garlon 4)
Factors Affecting Activity
Activity Foliar with limited soil activity.
Soils The product is predominantly foliar active and is affected very little by soil features. Triclopyr is potentially mobile since it is not bound to soil particles. However, it is readily broken down by soil microbes and is not considered persistent.
Timing On upland hardwoods, foliar treatment is most effective when applied after full foliar development in the spring but before the onset of hot dry summer weather. Garlon 4 is more effective on woody flatwoods species from midsummer to fall. Injection with Garlon 3A can be effective throughout the year except during periods of heavy sap flow in the spring.
Weather

No significant effects have been reported.

Environmental Concerns
Toxicity Very low. Garlon 3A can cause severe eye irritation by direct exposure.
Volatility Negligible for Garlon 3A; Garlon 4 is a low volatile ester, but cases have been reported where the product has moved off site during high temperatures. Ester formulation (Garlon 4) can be toxic to fish. Low toxicity to other wildlife, low volatility, and short persistence in soil are positive attributes.
Precautions Spraying directly up to adjacent property lines may result in damage or mortality to trees and shrubs that receive chemical on a portion of the crown.
Other Critical Factors
* Products control a wide range of woody and herbaceous species. Because of its foliar activity it is not strongly affected by soil type.
* Control of understory species promotes controlled burning although many grasses and certain forbs are resistant.
ALWAYS READ THE PRODUCT LABEL AND MATERIAL SAFETY DATA SHEETS BEFORE MAKING PRESCRIPTIONS.


Table 4
Application methods used to apply herbicides registered for
forest site preparation in the southern United States.1

Herbicide
Common Name
Trade Name
Application Methods
Dicamba Vanquish Aerial and ground broadcast
Glyphosate Accord SP Aerial and ground broadcast, handgun-spot spray
Hexazinone Pronone 5G Aerial and ground broadcast, individual stem
Hexazinone Pronone 10G Aerial and ground broadcast
Hexazinone Power Pellets Hand-apply (individual stem or grid pattern)
Hexazinone Velpar L Aerial and ground broadcast, spot (individual stem or grid, stem injection)
Hexazinone Velpar ULW Aerial broadcast
Imazapyr Arsenal Aerial and ground broadcast, backpack (individual stem)
Metsulfuron Escort Aerial and ground broadcast, backpack
Picloram Tordon K Aerial and ground broadcast
Picloram + 2,4-D (amine) Tordon 101 Mixture Aerial and ground broadcast, tree injection, frill
Triclopyr (amine) Garlon 3A Aerial and ground broadcast, tree injection,frill, stump treatment
Triclopyr (ester) Garlon 4 Ground and aerial broadcast, basal bark and dormant stem spray
Triclopyr (ester) + Picloram Access Basal bark treatment

1Application methods represent those listed on product labels. Generally, other methods can be legally used unless the label specifies otherwise.



Table 5
Recommended herbicide treatments for forest site preparation.

Site Conditions
Treatment
Comments
Upland sites with a mixed hardwood component

1 to 3 qt Accord + 16 to 20 oz Arsenal
or
4 qt Accord + 8 to 12 oz Arsenal

For poor to medium sites with oak, maple, sweetgum, cherry, poplar, sourwood and broadleaf weeds
5 qt Accord + 8 oz Arsenal For mixed species as above but with a significant component of elm and/or locust
3 to 4 lb active ingredient of hexazinone (Velpar ULW, Velpar L, Pronone 10G or Pronone 25G For early spring treatment of mixed hardwoods on well-drained sites. Use lower rates on coarse-textured soils and higher rates on fine-textured soils. See label.

2 gal Tordon 101M + 1/2 gal Garlon 4
or
1/2 gal Tordon K + 3/4 gal Garlon 4

For spring treatment of mixed hardwoods. Apply after full foliar development of target species.
1-1/2 to 2 qt Garlon 4 + 18 to 24 oz Arsenal

For mixed hardwoods as above plus blackberry, honeysuckle, maple and elm.

Coastal plain/ flatwood sites 1 to 2 qts Garlon 4 + 18 to 24 oz Arsenal For sites with gallberry, waxmyrtle, ti-ti, fetterbush and red maple
3 to 4 qts Accord + 8 to 12 oz Arsenal + 1 qt Garlon 4 + surfactant For sites with abundant magnolias and bays.


 

 

Release

 

 
Release

Release is a silvicultural treatment used to reduce the level of hardwood competition in young pine stands. The objective is to reduce pine mortality in situations where dense brush is overtopping pines and/or increase pine growth by controlling competition. The necessity for pine release often results from less than adequate site preparation, and hardwood control is generally more difficult once pines are established on the site. Hardwoods can be selectively controlled with certain herbicides that have greater activity on hardwoods than pines. Although selective broadcast applications of soil or foliar active products offer convenience, the user should be aware that pines are likely to sustain a certain amount of injury. The objective is to injure hardwoods to a greater degree so that pines can recover and dominate the site.

In addition to selective products, certain nonselective products are registered for directed spray applications with backpack sprayers. All of these products are described in this section. The user should pay close attention to details regarding pine selectivity, labeled application methods, and crop tree species for which individual products are labeled.


Table 6
Herbicides registered for pine release in the southern United States (1989)

Common Name
Trade Name
Manufacturer
Glyphosate Accord Dow AgroSciences
Hexazinone Pronone 25G Pro-Serve
Hexazinone Pronone 10G Pro-Serve
Hexazinone Power Pellets Pro-Serve
Hexazinone Velpar L DuPont
Hexazinone Velpar ULW DuPont
Imazapyr Arsenal BASF
Metsulfuron Escort DuPont
Triclopyr (amine) Garlon 3A1,3 Dow AgroSciences
Triclopyr (ester) Garlon 41,2 Dow AgroSciences

1Registered for directed sprays only.
2Registered for basal bark sprays.
3Registered for frill and injection.


 

 

Table 7
Herbicide products registered for conifer release and
crop tree species for which they are labeled.

Herbicide Product
Crop Tree Species
Accord loblolly, slash, white pine
Arsenal Applicators Concentrate loblolly, white pine1
Escort loblolly
Garlon 3A conifers2
Garlon 4 conifers2
Power Pellets loblolly, slash, shortleaf, longleaf pine
Pronone 25G loblolly, slash, shortleaf, longleaf, Virginia pine
Pronone 10G loblolly, slash, shortleaf, longleaf, Virginia pine
Velpar L loblolly, longleaf, shortleaf, slash, Virginia pine3
Velpar ULW loblolly, longleaf, shortleaf, slash, Virginia pine

1Do not apply broadcast treatments to stands less than 3 years old.

2Products are applied only as directed sprays with backpack equipment. Application to crop trees will cause injury or mortality.

3Broadcast applications are registered for loblolly, shortleaf, and Virginia pine. Grid applications are registered for loblolly, longleaf, slash, and shortleaf pine.


 

Table 8
Susceptibility of woody species to various release herbicides.1

Herbicide
Common Name
Highly Susceptible2
"Resistant"2
Glyphosate broad spectrum control of hardwoods red maple, black cherry, ash, hickory, dogwood
Hexazinone broad spectrum control of hardwoods yellow-poplar, eastern redcedar, sassafras, blackgum, hollies, American beautyberry
Imazapyr broad spectrum control of hardwoods elms, locust, redbud, pine, buckeye, waxmyrtle
Metsulfuron3 blackberry, black cherry, black locust, elm, dogwood, maple, ash not specified
Triclopyr (amine) broad spectrum control of hardwoods black cherry, eastern redcedar
Triclopyr (ester) broad spectrum control of hardwoods black cherry, eastern redcedar

1Information in this table is based on published data and on personal communication with various vegetation management specialists. As with all “susceptibility” tables, caution must be exercised when using this information. A concentrated effort was made to only include weed and crop species that are consistently controlled by, or consistently “escape” a particular herbicide.

2Highly susceptible indicates that the weed or crop species is very sensitive to the herbicide indicated at labeled rates; resistant indicates that the weed or crop species will be relatively unaffected by the herbicide indicated at labeled rates.

3Escort (metsulfuron) is labeled as a tank mix with Arsenal Applicators Concentrate (imazapyr) in order to improve control of species listed as “highly susceptible.” Escort by itself is not recommended for broad-spectrum woody brush control.

 

 

 

 

 

Herbicide
Characteristics
Affecting Prescriptions

 

 

 

 

GLYPHOSATE (Accord)
Factors Affecting Activity
Activity Foliar
Soils Product is not soil-active. Foliar activity is unaffected by soil texture and organic matter. Product is adsorbed tightly to soil particles. It is relatively immobile and nonpersistent.
Timing Product can be applied throughout the growing season but is most effective from late summer to mid-fall. Applications over-the-top of pines should not be made until pines have been established for one full year. Applications must be made after formation of final conifer resting buds in the fall.
Weather

Rainfall within 2 to 6 hours after treatment may wash herbicide from foliage and reduce efficacy.

Environmental Concerns
Toxicity Very low. Product can cause severe eye irritation by direct exposure.
Volatility Negligible
* Product has desirable traits regarding environmental effects. Glyphosate has low toxicity, is bound tightly to soils, and is not persistent.
Other Critical Factors
* Glyphosate is effective on a variety of hardwood species found on upland and mountainous sites.
* Quantitative data and or experience have not shown consistent results on certain sites in the deep South. However, efficacy can be enhanced with recently labeled tank mixes. See product label.
* Foliar activity requires thorough coverage of target vegetation. Some shielding may result from broadcast applications over multistory canopies.
ALWAYS READ THE PRODUCT LABEL AND MATERIAL SAFETY DATA SHEETS BEFORE MAKING PRESCRIPTIONS.

 

HEXAZINONE

(Velpar L, Velpar ULW, Pronone SG, Pronone 10G Power Pellets)

Factors Affecting Activity
Activity Soil and some contact foliar activity.
Soils

Products are very cost effective on coarse or light-textured soils with predominantly oak species. Hexazinone is mobile in soil. Persistence studies indicate that the half-life in soil ranges from 1 to 6 months depending on soil texture, moisture, temperature, etc. Activity is low or inconsistent on poorly drained soils.

Timing Apply during early spring to early summer when rainfall necessary for activation is available. Use on 1 year-old seedlings and on seedlings at least 4 years old. Injury may occur on 2 and 3 year-old seedlings where root growth is extensive but hardiness is lacking.
Weather Rainfall is necessary for activation.
Environmental Concerns
Volatility Negligible.
Toxicity Very low, but Velpar L can cause severe eye irritation by direct exposure. Products have a low toxicity rating for fish and wildlife.
Precautions Mobility with soil water can be a problem on certain sites. Attention should be paid to soil type and slope when considering possible movement to sensitive areas or into water table or agricultural and domestic use water.

Do not treat sites on which pines have been subjected to physiological stress due to drought, insects, diseases, etc.

Do not apply within the root zone of desirable hardwoods.

Other Critical Factors
* Hexazinone is very effective for controlling oaks on sandy or light textured soils. However, extreme care must be taken to assure an accurate application since pines can be quite susceptible on these soils.
* Soil activity can result in residual control of several hardwood and herbaceous weed species.
ALWAYS READ THE PRODUCT LABEL AND MATERIAL SAFETY DATA SHEETS BEFORE MAKING PRESCRIPTIONS.

 

IMAZAPYR (Arsenal Applicators Concentrate)

Factors Affecting Activity
Activity Both foliar and soil activity.
Soils

Imazapyr has both soil and foliar activity and is not strongly affected by soil texture and organic matter content. Arsenal appears to be very stable in soil. It does not move far laterally or vertically. The active ingredient does not deteriorate rapidly and is fairly persistent.

Timing Treatment can be conducted throughout the growing season. However, potential conifer injury can be minimized by treating after formation of final conifer resting buds in the fall. Do not broadcast over pine stands that are younger than 3 years old.
Weather No significant effects have been reported.
Environmental Concerns
Volatility Negligible.
Toxicity Arsenal has a very low order of toxicity to fish and wildlife.
* Low toxicity to fish and wildlife, immobility in the soil, and nonvolatility, are positive attributes.
Precautions Do not treat sites on which pines have been subjected to physiological stress due to drought, insects, diseases, etc.

Do not apply within the root zone of desirable hardwoods.

Other Critical Factors
* Pine plantations of all ages can be treated with directed sprays using low-volume, hand operated sprayers, thus avoiding direct application to the pine.
* Due to soil activity, broadcast applications will provide residual control of both hardwoods and herbaceous understory species.
ALWAYS READ THE PRODUCT LABEL AND MATERIAL SAFETY DATA SHEETS BEFORE MAKING PRESCRIPTIONS.

 

METSULFURON (Escort)
Factors Affecting Activity
Activity Primarily soil-active with some foliar activity.
Soils No data.
Timing Foliar applications should be made after full foliar development in the spring until fall colors develop late in the season.
Weather

Effectiveness may be reduced if rainfall occurs within 24 hours after application.

Environmental Concerns
Volatility Negligible.
Toxicity Low oral and dermal toxicity.
Other Critical Factors
* Use of a non-ionic surfactant is recommended for applications of Escort alone.
ALWAYS READ THE PRODUCT LABEL AND MATERIAL SAFETY DATA SHEETS BEFORE MAKING PRESCRIPTIONS.

 

TRICLOPYR (Garlon 3A, Garlon 4)
Factors Affecting Activity
Activity Foliar with limited soil activity.
Soils The product is predominantly foliarly active and is affected very little by soil features. Triclopyr is potentially mobile since it is not bound to soil particles. However, it is readily broken down by soil microbes and is not considered persistent.
Timing Foliar treatment is most effective from late spring after full foliar development to early summer before the onset of high temperatures and dry weather. Basal bark treatments appear to be most effective during the dormant season from February through March.
Weather

No significant effects have been reported.

Environmental Concerns
Toxicity Very low. Garlon 3A can cause severe eye irritation by direct exposure.
Volatility Negligible for Garlon 3A; Garlon 4 is a low volatile ester, but cases have been reported where the product has moved off site during high temperatures. Ester formulation (Garlon 4) can be toxic to fish. Low toxicity to other wildlife, low volatility, and short persistence in soil are positive attributes.
Other Critical Factors
* Directed foliar and dormant season basal bark treatments can be made with very low risk regarding pine damage. Pines should not be damaged unless treated by mistake.
* Treatment will effect only those stems treated directly. Minimum soil activity precludes residual control of additional hardwood stems or herbaceous weeds.
ALWAYS READ THE PRODUCT LABEL AND MATERIAL SAFETY DATA SHEETS BEFORE MAKING PRESCRIPTIONS.

 

Table 9
Application methods used to apply herbicides registered for
pine release in the southern United States (1989).
Common Name
Trade Name
Application Method1
Glyphosate Accord Aerial and ground broadcast, backpack, and directed foliar spray.
Hexazinone Pronone 25G Aerial and ground broadcast, individual stem
Hexazinone Pronone 10G Aerial and ground broadcast, individual stem
Hexazinone Power Pellets Hand-apply (individual stem or grid pattern)
Hexazinone Velpar L Aerial and ground broadcast, individual stem and grid pattern.
Hexazinone Velpar ULW Aerial broadcast
Imazapyr Arsenal Aerial and ground broadcast, directed sprays (backpack sprayers).
Metsulfuron Escort Aerial and ground broadcast, backpack
Triclopyr (amine) Garlon 3A Directed sprays (backpack sprayers).
Triclopyr (ester) Garlon 4 Basal bark treatments (backpack sprayers).

1Application methods represent those listed on product labels. Generally, other methods can be legally used unless specified otherwise on the label.


 

 


Table 10
Recommended herbicide treatments for pine release.

Herbicide Treatment
Comments

12.8 to 16 oz Arsenal

For control of mixed hardwoods on upland sites. Use the higher rates to control hickory, dogwood, red oak and live oak.
1 to 1-1/2 qts Accord + 8 to 12 oz
Arsenal + 8-10 oz Entry II
For control of mixed hardwoods on upland sites.
8-12 oz Arsenal + 1 oz Escort For control of mixed hardwoods on upland sites.
Escort provides improved control of blackberry, elm and cherry. Treatment can be applied early in the growing season.

1.3 to 4 lb Velpar ULW
2 to 6 qt Velpar L
10 to 30 lb Pronone 25G

For control of mixed hardwoods on well-drained sites.All three products should be applied from late spring to early summer as rainfall is required for activation. Apply the lower rates to coarse-textured soils and higher rates to fine-textured soil. See label.

 

 

 

 


Herbaceous
Weed Control

 

 
Herbaceous Weed Control

The practice of controlling herbaceous weeds in young pine plantations is fairly new. It has gained a means of increasing pine survival following regeneration and for accelerating early pine growth. Although these benefits are well documented and appear impressive, the utility of herbaceous weed control is somewhat limited. Herbicides registered for this use are primarily effective against annual grasses and forbs that are commonly pioneer invaders of newly disturbed sites. Applications work best in conjunction with intensive site preparation methods that expose mineral soil. Some of the products are also effective for converting former agricultural fields to pine. Products must be applied accurately by air or with agricultural boom type sprayers that are operable only on sites cleared of obstructions. Thus, herbaceous weed control is often not practical on forest sites with residual hardwoods from the previous stand, or on sites with herbicide resistant grasses and forbs.

The following information should provide general guidelines on how to use registered products appropriately.

 

 

Table 11
Herbicides registered for herbaceous weed control in
pine outplantings in the southern United States.

Common Name
Trade Name
Manufacturer
Atrazine AAtrex 4L Syngenta
Atrazine AAtrex Nine-O Syngenta
Fluazifop-butyl Fusilade DX Syngenta
Glyphosate Accord Dow AgroSciences
Hexazinone Pronone 5G Pro-Serve
Hexazinone Velpar L DuPont
Imazapyr Arsenal Applicators Concentrate BASF
Metsulfuron Escort DuPont
Sethoxydim Vantage BASF
Sulfometuron methyl Oust, Oust XP, Oustar1 DuPont

1Oustar is prepackaged mixture of 63.2% hexazinone and 11.8% sulfometuron methyl.


 

Table 12
Herbicide products registered for herbaceous weed control in pine outplantings and crop tree species for which they are labeled.

Herbicide Product
Crop Tree Species
AAtrex 4L loblolly, slash pine
AAtrex Nine-O loblolly, slash pine
Accord1 loblolly, slash pine
Arsenal Applicators Concentrate loblolly, longleaf, white pine4
Fusilade DX conifers
Escort2 loblolly pine
Oust3 loblolly, longleaf, slash, Virginia pine
Poast loblolly, longleaf, slash, Virginia pine
Pronone 5G loblolly, longleaf, slash, Virginia pine
Velpar L loblolly, shortleaf, Virginia pine
Oustar loblolly, longleaf, slash
Oust XP loblolly, longleaf, slash, Virginia, white pine

1Product can be tank mixed with Oust for application over loblolly pine.

2Registered for use on seedlings that have been established for one year or more in the field. Can be used on first year seedlings if tank mixed with Arsenal.

3Tank-mixes with Atrazine are registered for slash and loblolly pine, and tank-mixes with Velpar are registered for loblolly, slash, and longleaf.

4Registered for broadcast application over loblolly pine, but as a directed spray only around white pine.


 


Table 13
Important species susceptibility features of herbicides
used to control herbaceous weeds in pine outplantings.1

Herbicide
Common Name
Highly Susceptible2
"Resistant"2
Atrazine
Broad spectrum control of annual grasses and forbs including morningglory, sicklepod,
cocklebur, and crabgrass
bermudagrass, broomsedge,
Johnsongrass
Fluazifop-butyl
Annual and perennial grasses All broadleaf weeds
Glyphosate Broad spectrum control of annual grasses and forbs and some perennials. Greenbriar, Virginia creeper, trumpetcreeper
Hexazinone Broad spectrum control of annual grasses and forbs and some perennials. Bermudagrass, white snakeroot, broomsedge, Johnsongrass, sicklepod, trumpetcreeper, morningglory, coffeeweed
Imazapyr Broad spectrum control of annual and perennial grasses and forbs Legumes such as sicklepod and coffeeweed, tropic croton, Rubrus spp.
Metsulfuron Broad spectrum control of annual grasses and forbs and certain perennials such as blackberry, honeysuckle and bahiagrass. Bermudagrass, croton spp., Johnsongrass, trumpetcreeper, broomsedge
Sethoxydim Annual and perennial grasses All broadleaf weeds
Sulfometuron methyl Broad spectrum control of annual grasses and forbs and certain perennials Bermudagrass, croton spp., Johnsongrass, trumpetcreeper, broomsedge, cocklebur, pigweed, sicklepod, coffeeweed

 

 

 

Herbicide

Characteristics

Affecting Prescriptions

 

 

 

ATRAZINE (AAtrex 4L, AAtrex Nine-O)

Factors Affecting Activity
Activity Preemergence to weeds – will not control established weeds.
Soils

Product is not highly mobile in soil. Higher rates are recommended on organic soils.

Timing Product should be applied prior to weed emergence or before weeds reach 1.5 inches in height.
Weather Product must have adequate rainfall to move into the rooting zone of germinating seedlings.
Environmental Concerns
Volatility Negligible.
Toxicity Very low order of toxicity.
Other Critical Factors
* Atrazine is classified as a restricted use pesticide. The applicator must be certified in order to use the product. Consult the product label before using.
* Atrazine controls a variety of annual grasses and forbs when applied preemergence to weeds. However, it rarely provides season-long weed control when used alone. Atrazine is recommended in tank mixes with sulfometuron methyl (Oust) for increased control of cocklebur, morningglory, sicklepod, and crabgrass.
ALWAYS READ THE PRODUCT LABEL AND MATERIAL SAFETY DATA SHEETS BEFORE MAKING PRESCRIPTIONS.

 

FLUAZIFOP-BUTYL (Fusilade 2000)

Factors Affecting Activity
Activity Foliar
Soils

Product is not very mobile in soil.

Timing Product is active postemergence to grass weeds. Apply the product to grasses before they exceed recommended growth stages designated on the label.
Weather No important effects.
Environmental Concerns
Volatility Low volatility.
Toxicity Low oral toxicity. Product is corrosive and can cause severe eye damage and skin burns.
* See label for precautions.
Other Critical Factors
* Fluazifop-butyl will effectively control a variety of annual and perennial grasses when applied as a postemergence treatment. Multiple applications are recommended for bermudagrass control. Tank mixes with broadleaf herbicides may be necessary to provide residual control of other weeds.
ALWAYS READ THE PRODUCT LABEL AND MATERIAL SAFETY DATA SHEETS BEFORE MAKING PRESCRIPTIONS.

 

GLYPHOSATE (Accord)
Factors Affecting Activity
Activity Foliar-active
Soils Adsorbed tightly to soil particles, very little leaching, relatively nonpersistent.
Timing Glyphosate is strictly a postemergence herbicide. Mixtures of glyphosate plus sulfometuron methyl can be used for residual weed control.
Weather

Rainfall within 2 to 6 hours after treatment may wash herbicide from foliage and reduce efficacy.

Environmental Concerns
Toxicity Generally very low.
Volatility Negligible
* Low toxicity to fish and wildlife, no volatility, and relatively short persistence in soil are positive attributes.
Other Critical Factors
* Glyphosate can be applied as a directed spray to control many perennial weed species that cannot be controlled with selective over-the-top treatments.
* Selective, over-the-top rates of glyphosate may be tank mixed with sulfometuron methyl (Oust) for residual weed control. Glyphosate does not provide residual control when used alone.
* Over-the-top applications must be applied accurately with a boom-type sprayer or pine injury and mortality will result. Read label carefully for appropriate ratio.
ALWAYS READ THE PRODUCT LABEL AND MATERIAL SAFETY DATA SHEETS BEFORE MAKING PRESCRIPTIONS.

 

HEXAZINONE (Velpar L)

Factors Affecting Activity
Activity Primarily soil-active with some contact foliar activity.
Soils

Hexazinone is fairly mobile in soil. Persistence studies indicate that the half-life in soil ranges from 1 to 6 months, depending upon soil texture, temperature, etc.

Timing Apply product from early spring until early summer. Hexazinone can be applied both pre- and postemergent to weeds although pre- and early postemergence applications appear to be most effective.
Weather Product requires rainfall for activation in the soil.
Environmental Concerns
Volatility Negligible.
Toxicity Generally very low. Velpar L can cause severe eye irritation by direct exposure.
Other Critical Factors
* Herbaceous weed control is most effective when used in conjunction with intensive site preparation which exposes mineral soil and favors an influx of annual grasses and forbs.
* Hexazinone controls a wide range of annual grasses and forbs, but selective rates will not control a variety of residual perennial species from the previous stand or those characteristic of later successional stages found in older plantations.
* Selective rates of hexazinone that will control weeds without pine injury must be applied accurately with a boom-type sprayer.
* Rate selection is based on soil texture and percent organic matter, with risk of pine injury being higher on coarse textured soils. On sandy or coarse textured soils, an alternative herbicide such as sulfometuron methyl can be used with less risk of pine injury.
ALWAYS READ THE PRODUCT LABEL AND MATERIAL SAFETY DATA SHEETS BEFORE MAKING PRESCRIPTIONS.

 

IMAZAPYR (Arsenal Applicators Concentrate)

Factors Affecting Activity
Activity Both soil and foliar activity, i.e. pre- and postemergence activity.
Soils

Imazapyr is fairly stable in soil and is not strongly affected by texture or organic content. Lateral and vertical movement is negligible.

Timing Imazapyr is fairly stable in soil and is not strongly affected by texture or organic content. Lateral and vertical movement is negligible.
Weather No reported effects.
Environmental Concerns
Volatility Negligible.
Toxicity Imazapyr has a very low order of toxicity to fish and wildlife.
* Low toxicity to fish and wildlife, no volatility, and relatively short persistence in soil are positive attributes.
Other Critical Factors
* Herbaceous weed control is most effective when used in conjunction with intensive site preparation which exposes mineral soil and favors an influx of annual grasses and forbs.
* Imazapyr can stunt growth of pines when applied at the highest labeled rates. Lower rates tank-mixed with sulfometuron methyl (Oust) are recommended for effective weed control and maximum pine growth.
ALWAYS READ THE PRODUCT LABEL AND MATERIAL SAFETY DATA SHEETS BEFORE MAKING PRESCRIPTIONS.

 

METSULFURON (Escort)
Factors Affecting Activity
Activity Primarily soil-active with some foliar activity.
Soils No data.
Timing Early postemergence applications are most effective.
Weather

No important effects.

Environmental Concerns
Volatility Negligible.
Toxicity Low oral and dermal toxicity.
Other Critical Factors
* Use of a non-ionic surfactant is recommended for applications of Escort alone.
ALWAYS READ THE PRODUCT LABEL AND MATERIAL SAFETY DATA SHEETS BEFORE MAKING PRESCRIPTIONS.

 

SETHOXYDIM (Poast)
Factors Affecting Activity
Activity Foliar
Soils No data.
Timing Product is active postemergence to grass weeds. Apply the product to grasses before they exceed recommended growth stages designated on the label.
Weather

No important effects.

Environmental Concerns
Volatility Low volatility.
Toxicity Low oral toxicity. Product is corrosive and can cause severe eye and skin damage.
Other Critical Factors
* Sethoxydim will effectively control a variety of annual and perennial grasses when applied as a postemergence treatment. Combined treatments with broadleaf herbicides may be necessary to provide residual control of other weeds.
ALWAYS READ THE PRODUCT LABEL AND MATERIAL SAFETY DATA SHEETS BEFORE MAKING PRESCRIPTIONS.

 

SULFOMETURON METHYL (Oust)
Factors Affecting Activity
Activity Primarily soil-active with some foliar activity.
Soils Product is fairly mobile in soil and will move both vertically and with surface runoff.
Timing Product is most effective when applied immediately before or just after weed emergence in the spring. Efficacy declines considerably with maturity of weed species.
Weather

Heavy rainfall can wash product from some sites.

Environmental Concerns
Volatility Negligible
Toxicity Low oral and dermal toxicity.
* See label for precautions.
Other Critical Factors
* Sulfometuron methyl will control a wide variety of annual grasses and forbs. Applications are most effective when used on sites that have been intensively site prepared or that favor growth of annual species. Weed species common to later successional stages are not easily controlled with this product.
* Do not apply over the top of pines that are obviously under physiological stress due to drought, insects, or disease.
ALWAYS READ THE PRODUCT LABEL AND MATERIAL SAFETY DATA SHEETS BEFORE MAKING PRESCRIPTIONS.

 

Application Methods

Most products registered for herbaceous weed control are applied at a rate per unit area of surface treated, for example, pounds or ounces per acre. Most often they are applied in bands or strips centered over crop tree rows. These must be accurately applied with a well calibrated boom type sprayer. The only exceptions are Accord and Poast, which can be direct sprayed around seedlings.

 

Table 14
Recommended herbicide treatments for herbaceous weed control
in young pine plantations.

Soils
Conditions
Treatment
(per acre rates)1
Crop Species
---------------------------------------------- Upper Coastal Plain - Piedmont ----------------------------------------------
sandy bare soil Oust @ (2-3 oz) + Velpar @ 32 oz
Oust @ (3-4 oz
Oust @ (2-3 oz) + Arsenal @ (4-6 oz)
Arsenal @ 6-8 oz
loblolly, slash, longleaf
Virginia, loblolly, slash
longleaf
loblolly, slash
clay bare soil Oust @ 2 oz + Velpar L @ 48 oz
Velpar L @ 48-642 oz
Arsenal @ 8 oz
Oust @ (1.5-2 oz) + Arsenal @ (4-6 oz)
loblolly, slash, longleaf
shortleaf, loblolly, Virginia
loblolly
loblolly
clay or sands established herbs

(Fescue + forbs)
Arsenal @ (8-10 oz)
Oust @ (1.5-2 oz) + Arsenal @ (4-6 oz)
Oust @ 2 oz + Velpar L @ 32-48 oz
Oust @ 2 oz + Accord @ 16 oz
Arsenal @ (6-8 oz)

loblolly
loblolly, slash
longleaf
loblolly, slash
loblolly, slash

----------------------------------------------------- Old fields - pastures3--------------------------------------------------------
Previous cropland sicklepods, cocklebur
morningglory
Oust @ 2 oz + atrazine @ 2-4 lbs
loblolly, slash
Previous cropland Johnsongrass Arsenal (4-6 oz) + Oust (2-3 oz) loblolly, slash
Pasture non-bermudagrass Oust @ 2 oz + Velpar L @ 32 oz
Oust @ 2 oz + Arsenal @ (4-6 oz)
loblolly, slash, longleaf
loblolly, slash
Pasture bermudagrass Arsenal @ (7-8 oz)
Arsenal @ (4- oz) + Oust (2-3 oz)
loblolly
loblolly
Pasture bermudagrass4 Accord @ 5 qts/ac + surf.
Arsenal @ (12-16 oz) + surf.
All species
loblolly, slash, longleaf
Spodosols5
Spodosols
Spodosols
Spodosols
bare soil
bare soil
bare soil
bare soil
Oust @ (2-3 oz) + Velpar L @ 32 oz
Arsenal @ 6 oz
Arsenal @ (6-8 oz)
Oust @ (2-3 oz) + Arsenal @ (4-6 oz)
loblolly, slash, longleaf
slash
loblolly
loblolly, slash
Spodosols
Spodosols
Spodosols
established grasses
established grasses
established grasses
Arsenal @ 8 oz/ac
Arsenal @ 6-8 oz/ac
Oust @ 2 oz + Arsenal @ 6 oz

loblolly, slash
slash
loblolly, slash

non-spodosols-clays bare soil Oust @ 2 oz + Velpar L @ 48 oz
Arsenal @ 6 oz
Arsenal @ 6-8 oz
Oust @ (1.5-2 oz) + Arsenal @ (4-6 oz)
loblolly, slash, longleaf
slash
loblolly
slash, loblolly

This table was printed by permission of the Auburn University Silvicultural Herbicide Cooperative, School of Forestry, Auburn University, AL 36849-5418. Prescriptions in the table are from AUSHC Information Note 95-3. Recommendations are based on labelled rates, studies reported in the literature, and experience with current operational forestry practices. Other combinations may be available. These rates will usually work under the specified conditions and research has shown them to provide increases in growth and/or survival under many but not all conditions. Rate recommendations do not supercede label restrictions - read and follow label instructions before application.

1Highest range rate provides best weed control. Combinations are usually prescribed using a high rate for one herbicide with the low rate for the other.

2Up to 10% loblolly mortality could occur at high range of this rate.

3Higher rate recommendations for established vegetation may cause some pine damage in order to control herbs.

4Apply in August as a pre-plant treatment.

5Soils commonly found in the coastal plain of the southeastern United States that are characterized by ashy gray sands over dark sandy loams. A soils expert should be consulted for positive identification.


 


Selected References and Literature Cited
  • Cantrell, R. L. 1985. A guide to silvicultural herbicide use in the southern United States. Auburn University School of Forestry, Alabama Agric. Exp. Stn., Auburn, AL. 592 pp.
  • Cantrell, R. L. and G. M. Hopper. 1989. Forest herbicides are safe to use—Here’s why. Ren. Res. Notes. Univ. Tennessee Agric. Ext. Serv. SP 368. 8 pp.
  • Hurst, G. A. 1989. Forestry chemicals and wildlife habitat. Forest Farmer. 48:10-11.
  • Hurst, G. A. 1988a. Vegetation following imazapyr for site preparation. South. Weed Sci. Proc. 41:201. Hurst, G. A. 1988b. Vegetation responses to hexazinone for site prep. South. Weed Sci. Soc. Proc. 41:210.
  • Miller, J. H. and R. J. Mitchell, 1988. A manual on ground applications of forestry herbicides. USFS Mgmt. Bull. R8-MB21.
  • Walstad, J. D. and F. N. Dost. 1984. The health risks of herbicides in forestry: a review of the scientific record. Special Pub. 10. College of Forestry, Oregon St. Univ. 60 pp.
  • Williamson, M. and J. H. Miller. 1987. Hand application methods for commonly used forestry herbicides in the south. USFS, Atlanta, GA. 15 pp.
  • Witkowski, C. A., G. P. Sick and J. D. Fenwood. 1988. Herbicide risk to wildlife—a new look. U. S. Poster Presen., SAF Nat. Conv.; Rochester, NY. 9 pp.

 

Appendix A - Herbicide Application Records Sheet


 


Appendix B
Common and Scientific Names of Weed and Crop Species
Included in this Manual

Alphabetical by Common Name

Common Name
Scientific Name
American beautyberry Callicarpa americana
Ash Fraxinus spp.
Bermudagrass Cynodon dactylon
Black cherry Prunus serotina
Blackgum
Nyssa sylvatica
Black locust Robinia pseudoacacia
Broomsedge Andropogon virginicus
Buckeye Aesculus spp.
Cherry Prunus spp.
Cocklebur Xanthium spp.
Crabgrass Digitaria spp.
Croton Croton spp.
Dogwood Cornus spp.
Eastern redcedar Juniperus virginiana
Elm Ulmus spp.
Greenbrier Smilax spp.
Hickory Carya spp.
Holly Ilex spp.
Johnsongrass Sorghum halapense
Loblolly pine Pinus taeda
Longleaf pine Pinus palustris
Morningglory Ipomoea spp.
Multiflora rose Rosa multiflora
Persimmon Diospyros virginiana
Redbud Cercis canadensis
Red maple Acer rubrum
Sassafras Sassafras albidum
Shortleaf pine Pinus echinata
Sicklepod Cassia spp.
Slash pine Pinus elliottii
Sumac Rhus spp.
Sweetgum Liquidambar styraciflua
Titi Cyrilla racemifora
Tropical croton Croton grandulosus
Trumpetcreeper Campsis radicans
Virginia creeper Parthenocissus quinquefolia
Virginia pine Pinus virginiana
Waxmyrtle Myrica cerifera
White oak Quercus alba
White pine Pinus strobus
White snakeroot Eupatorium rugosum
Willow Salix spp.
Yellow-poplar Liriodendron tulipifera

 


 


Appendix C

Herbicide Terminology

A. E. (Acid equivalent) That proportion of a compound or formulation that theoretically can be converted back to the corresponding acid.
Active ingredient Actual amount of toxic material in a formulation.
Adhesive A sticking agent; causes sprayed material to stick to sprayed surface.
Adjuvant A material that assists, aids, or modifies the spray solution in some manner.
Amine A formulation of a herbicide made from an organic acid plus ammonia. Amine formulations are readily soluble in water.
Annual plant A plant that completes its life cycle in one year.
Band treatment Applied to a continuous restricted area such as on or along a crop row rather than over the entire field area.
Basal treatment Applied to encircle the stem of a plant above and at the ground so that foliage contact is minimal.
Biennial plant A plant with a two-year life cycle.
Broadcast treatment Applied over an entire area.
Brush control Control of woody plants such as sprout clumps, shrubs, undesirable trees and vines.
Cambium Tissue lying just under the bark which produces new wood and bark cells in the tree.
Compatibility Refers to chemical materials that can be mixed together without adversely changing them or their effects on pests or plants.
Concentration The amount of active ingredient or herbicide equivalent in a quantity of carrier (such as water, oil, or dust) expressed as percent, lb/gal, ml/L, etc.
Contact herbicide A herbicide that injures plant tissues upon contact.
DBH (Diameter breast height) Diameter of trees at a point 4.5 feet above ground level.
Directed application Precise application to a specific area or plant organ such as to a row or bed or to the lower leaves and stems of plants.
Dormant season That period of the year when plants are not actively growing, generally from late autumn through the winter months.
Dormant spray A chemical applied during the dormant season.
Emulsifiable concentrate (EC) A formulation produced by dissolving the toxicant and an emulsifying agent in an organic solvent.
Emulsion The suspension of one liquid as small drops in another liquid (for example, oil dispersed in water).
Epinasty Twisting or curling of leaves or stems caused by a differential in rate of cell growth.
Ester A formulation of a herbicide made from an organic acid plus an alcohol. Ester formulations are readily soluble in oil.
Foliar application Application of a herbicide to the leaves or foliage of plants.
Formulation A herbicidal preparation of active and inert ingredients supplied my a manufacturer.
Frill Series of overlapping axe cuts completely around the circumference of trees. Axe cuts can be filled herbicide from any suitable container if tree injection equipment is not available.
Girdling Complete removal of a band of bark from around a woody stem.
Granule or Granular A dry formulation of herbicide and other components as small particles, generally less than 10 cubic millimeters.
Growing season That period of the year when plants are actively growing, generally from early spring to autumn.
Hardened off Term denoting stage of plant development when terminal buds have formed and stem and root tissues have ceased growth. Dormant stage of pine seedlings is often denoted by purplish or bronze-colored needles.
Herbaceous Plants with non-woody stems that normally die back to the ground in the winter. Herbicide — A chemical used for killing plants or severely interrupting their normal growth processes.
L Liquid.
LD50 (Lethal Dosage) A measure of toxicity. Dosage at which 50% of the test animals are killed. Commonly expressed as mg/kg of body weight.
Label All information printed on or attached to the herbicide container. It contains the brand name, amount of active ingredients, contents, manufacturer’s address, registration numbers, hazard warnings, directions for use, and emergency first-aid measures.
Metering injector Tool designed to pierce tree bark and release a small, measured amount of undiluted herbicide.
Mistblower A power sprayer that is capable of producing a spray of very small droplet size.
ml (milliliter) 1/1000 of a liter. 14.8 ml = 1 tablespoon = 0.5 fl. oz.
Necrosis Death of tissue.
Nonmetering injector Tool designed to pierce tree bark and release an unmeasured amount of diluted herbicide.
Nonselective herbicide A chemical that is generally toxic to plants without regard to species (may be due to dosage rate, method of application, etc.)
OS Oil soluble.
Pellet A dry formulation of herbicide and other components as particles usually larger than 10 cubic millimeters.
Perennial plant A plant that lives for more than two years and may live indefinitely.
Persistent herbicide A herbicide which breaks down slowly and interferes with regrowth of native vegetation.
Pesticide Any substance or mixture of substances used to control plant and animal life.
Phytotoxic Poisonous to plants.
Pine release Reduction or elimination of competing woody vegetation in young pine stands to provide pines with improved growing conditions.
Post-emergence herbicide A chemical applied to foliage after the weeds or crop have emerged from the soil.
Pre-emergence herbicide A chemical applied before emergence of weeds from the soil.
Preplanting application Applied on a site before seeding or transplanting.
Rate The amount of herbicide equivalent or acid equivalent applied per treatment unit.
Residual herbicide A weed killer that persists in the soil, killing weeds as they germinate.
Root collar Portion of tree stem at ground level or the junction of the above- and below-ground portions of the tree.
Selective herbicide A chemical that is more toxic to some plant species than to others (may be due to dosage rate or method of application).
Single-hack girdle A single line of overlapping axe cuts made through the bark and into the wood. Same as a frill.
SP Soluble powder.
Spot treatment Application of herbicides to a small ground area.
Spray drift Movement of airborne spray away from the intended area of application.
Stand conversion The transformation of a forest from one type to another favoring a particular species or group of species.
Surfactant A material which favors or improves the emulsifying, dispersing, spreading, wetting, or other surface-modifying properties of liquids.
Suspension A liquid in which very fine solid particles are dispersed but not dissolved.
Translocated herbicide A herbicide that is moved within the plant.
Tree injection Method of placement of herbicides under bark into the actively growing portion of the tree.
Vapor drift The movement of chemical vapors away from the area of application.
Volatile herbicide A herbicide that vaporizes readily when applied at normal rates and normal temperatures so that its vapor may cause serious injury to desirable plants away from the site of the application.
Weed A plant growing where it is not desired. Plants are considered weeds when they interfere with activities of man or his welfare.
Weed control The process of limiting weed infestations or killing weeds for aesthetic, economic, public health, or other reasons.
WP (Wettable powder) A finely-divided, dry herbicide formulation that can be suspended readily in water.
WS Water soluble.

 

 

Appendix D
Chemical Companies

BASF BASF Forestry
26 Davis Drive
Research Triangle Park, NC 27709
(800) 545-9525
Syngenta Syngenta
Corporate Headquarters
1800 Concord Pike
Wilmington, DE 19850
Dow AgroSciences

Dow AgroSciences, LLC
9330 Zionsville Road
Indianapolis, IN 46268

DuPont E. I. DuPont de Nemours and Company
Biochemicals Department
Wilmington, DE 19898
(302) 774-1000
Pro-Serve Pro-Serve, Inc.
P 0. Box 161059
400 E. Brooks
Memphis, TN 38116
(901) 332-7052