Herbicide Prescription Manual
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
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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
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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.
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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.”
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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
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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
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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. Soilactive 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
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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.
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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
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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 broadspectrum 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.
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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.
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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.
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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 offsite and extreme sensitivity of certain crops. See precautions
on label.
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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.
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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.
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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.
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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.
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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
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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.
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*
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.
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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
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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
Upland sites with
a mixed
hardwood
component
Coastal plain/
flatwood sites
Treatment
Comments
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 finetextured 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.
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.
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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
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Triclopyr (amine)
Garlon 3A1,3
Dow AgroSciences
Triclopyr (ester)
Garlon 41,2
Dow AgroSciences
1Registered
for directed sprays only.
for basal bark sprays.
3Registered for frill and injection.
2Registered
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.
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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 broadspectrum woody brush control.
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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 overthe-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.
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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.
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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.
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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.
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*
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.
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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.
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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.
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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.
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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
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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
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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
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
(Fescue + forbs)
----------------------------------------------------- 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
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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-spodosolsclays
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
4Apply
rate recommendations for established vegetation may cause some pine damage in order to control herbs.
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.
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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
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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
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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.
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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.
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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 aboveand below-ground portions of the tree.
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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.
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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
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