• Topics: School of Forest Resources and Conservation | North Florida REC-Quincy | Forest Vegetation Management | Mossler, Mark Allen | Long, Alan J | Nowak, Jarek | Osiecka, Anna | Minogue, Patrick J

Herbicides Registered for Pine Management in Florida – 2008¹

According to Hodges et al. (2005), Florida has one of the largest concentrations of intensively managed plantations of southern pines in the world. Pine plantations comprise approximately 32 percent of the forested land or 15 percent of the total land base in Florida (Carter and Jokela 2002). Vegetation management is an integral part of successful pine plantation management. Following the development and registration of many new forestry herbicides during the 1980s, herbicide use for forest vegetation management increased dramatically. This trend continues because of the introduction of lower-cost generic herbicides, and because the costs of mechanical treatment alternatives are increasing, driven up, for the most part, by increased fuel costs. Herbicides are used to enhance crop tree survival and growth rates, allowing producers to improve return on investment with minimal site disturbance. Their application facilitates many forestry operations, such as pine straw harvest, logging, and plantation reestablishment. They can also reduce the risk of destructive wildfires and improve wildlife habitat, aesthetics, and recreation opportunities. Herbicides are an effective tool in controlling invasive plants and restoring native ecosystems. They can be applied at different stages during pine plantation rotation for:

• Site preparation before planting

• Herbaceous weed control during establishment

• Release of established pines from competing vegetation

Efficient, safe and environmentally sound herbicide use requires an up-to-date knowledge of weed control technology. Landowners must stay aware of developments because new herbicides are constantly being developed and registered for use in Florida, and, just as crucially, in many years some of the older herbicides are discontinued, or their registration in the state of Florida terminated.

The aim of this publication is to provide comprehensive information about the herbicides currently registered for use in Florida pine plantations. All herbicide active ingredients important in pine management in Florida with examples of commercial products are listed in Table 1, and their use characterized in Table 2. Other active ingredients that are registered in Florida but are rather marginally used for pine plantations, like 2,4-D, atrazine, dicamba, paraquat, and simazine, are also included. Since an increasing number of private and public owners manage their forestlands for non-commodity purposes, herbicides that are intended mostly for turf and/or landscape maintenance, but also labeled for conifer plantations (e.g. pendimethalin), have been included as well.

Most of the herbicide active ingredients are available in different formulations from different manufacturers and/or distributors under a variety of trade names. It is beyond the scope of this publication to mention all of the silvicultural herbicide products available on the market. It has to be emphasized that there might be considerable differences even among herbicides with the same concentration of the same active ingredient(s) resulting, for example, from differences in adjuvants or solvents. Therefore, before making any herbicide substitutions, one has to be sure that the selected product is appropriate for the intended application, and one must read and follow all label recommendations. Inclusion of a product trade name or a company name in this publication does not constitute an endorsement of a product or a company, as other products manufactured by different companies might be equally suited for the intended herbicide use.

The examples of herbicides registered for pine management in Florida are listed alphabetically, first by active ingredient and then by trade name (Table 1). Products with the same Environmental Protection Agency (EPA) registration number are grouped together. Herbicides containing more than one active ingredient are placed according to the highest percentage of active ingredient.

Table 2 provides information on basic weed control characteristics and silvicultural applications for listed herbicides. Herbicides can be used for a variety of applications in managing pine forests to control or alter undesirable vegetation. Site preparation (S) is one use where the current vegetation can be controlled by herbicides prior to planting pine seedlings. After planting, herbaceous weed control (H) with herbicides can aid the survival and growth of the young pine seedlings during the establishment phase. Subsequently, herbicides can be applied to release (R) established pine trees from competing woody vegetation, including early and mid-rotation release as well as timber stand improvement later in the rotation. Some truly selective herbicides may be broadcast over pines at recommended rates and timing without significant adverse effects to pines. Directed spray [(d)] and understory broadcast [(u)] are two release techniques that can be used to obtain selectivity by herbicide placement, minimizing contact with crop trees. Individual stems (I) of undesirable vegetation can be treated with herbicides throughout the pine rotation, from site preparation to harvest. Soil-active herbicides can be used for basal soil treatment [(bs)] in the immediate vicinity of the individual stems. Some herbicides are labeled for applications in wetlands (W) or aquatic (A) areas in the forests.

Basic terms used in this and other herbicide publications can be defined as follows:

Active ingredient (a.i.) is the chemical substance in the herbicide that does the work: the a.i. changes plant metabolism and is designed to control the undesirable vegetation. The active ingredient has the greatest influence on the properties and behavior of the herbicide and is the primary reason a given herbicide will be selected for a particular application. The exact chemical name of the active ingredient is useful to chemists to ensure precise communication. The common name is a simplified, less technical name of an active ingredient, most often used in herbicide recommendations and technical literature. (Common names are used in Tables 1 and 2 of this publication.) For example, imazapyr is a common name for 2-[4,5-dihydro-4-methyl-4-(1-methylethyl)-5-oxo-1H-imidazol-2-yl]-3-pyridinecarboxylic acid.

Formulation is the commercial preparation of the herbicide product, including one or more active ingredients, usually a solvent (for liquid products), and, possibly, adjuvant(s), such as wetting agents (surfactants). Each formulation is registered and marketed under a separate trade name. Frequently the same formulation or formulations containing the same concentration of the same form of an active ingredient may be marketed under several trade names by different companies or even the same manufacturer or distributor, which may be quite confusing. Such is the case with Dow’s Accord^® Concentrate, Glypro^® and Rodeo^®; all three contain the same salt of glyphosate (53.8% of the isopropylamine salt) and are registered under the same EPA registration number. While new forestry herbicide active ingredients are not frequently introduced, new formulations, which are often more effective and safer, are rapidly being developed. Several new herbicide formulations have higher content of active ingredients and are often available in large, returnable, refillable containers, which reduces the need for container disposal. A growing number of products contain two active ingredients, eliminating the need for mixing. Recently introduced Lineage^TM Prep and Lineage^TM HWC are the first forestry herbicides formulated with three active ingredients. New adjuvants (additives) tend to improve efficacy and the ease of use, often reducing the treatment cost at the same time.

Trade names of herbicides may include numbers and/or letters to further identify the product. The number immediately after the name refers to the concentration of active ingredient. The amount of active ingredient in a herbicide may be expressed as a percentage of volume or mass of the commercial product. For example, MSM 60 contains 60%, by weight, of the active ingredient metsulfuron methyl. Labels may additionally provide an acid equivalent (a.e.), which refers to the theoretical yield of a parent acid from a herbicide active ingredient that has been formulated as a derivative, such as an amine or ester. Acid equivalent content is especially useful when comparing herbicides containing different chemical forms of the same active ingredient. For example, Garlon^® 3A contains 44.4% of the triethylamine salt of triclopyr, or 31.8% (3 lb/gal) of the acid equivalent, triclopyr. Garlon^® 4 contains 61.6% of butoxyethyl ester of triclopyr, or 44.3% (4 lb/gal) of the acid equivalent, triclopyr. In this case, the numbers in the trade names refer to the weight of the acid equivalent per volume of the product, with the parent acid, triclopyr, being the herbicidal portion of the formulation.

Letter(s) included in a trade name often (but not always) indicate formulation of the product. Not all companies use the same abbreviations, so it may be necessary to refer to the full label text. Also, acronyms found in labeling often differ from the standard two-letter international (CIPAC) formulation codes. Some of the more common acronyms are:

DF dry flowable

DG dry granular

E or EC emulsifiable concentrate

F or FL flowable or flowable liquid

G granular

L liquid

LV low volume concentrate

P or PS pellet

RTU ready to use

S, SL, WS soluble concentrate or ready to use solution

SP soluble powder

ULV ultra low volume concentrate

ULW ultra light weight

W or WP wettable powder

WDG water dispersible granule (similar to dry flowable)

WSP water soluble powder

XP extruded pellet

Labeling associated with each herbicide includes one or more product labels, a Material Safety Data Sheet (MSDS), and possibly additional publications. These documents are the primary method of communication between a herbicide manufacturer or distributor and a herbicide user. They contain detailed information about the herbicide product, including trade name, common name(s), chemical name(s), active ingredient(s), concentration(s) and EPA registration number. Product labels provide information about the herbicide application and safety, whereas the MSDS focuses on chemical and physical properties of the herbicide and personal and environmental safety. Because the MSDSs include emergency medical information and information physicians need to deal with accidental exposure to herbicide products, the MSDS for each herbicide used should be available on site wherever herbicides are used (and wherever they are stored or transported). Information and instructions contained in the labeling must be strictly followed when purchasing, transporting, storing, mixing, applying or disposing of herbicides. It is a violation of federal law to use any herbicide in a manner inconsistent with its labeling.

Full text labels and MSDSs for most herbicides are accessible through manufacturers' or distributors' web sites and dedicated databases such as those of Crop Data Management Systems (CDMS) at http://www.cdms.net/LabelsMsds/LMDefault.aspx, or Greenbook^® at http://www.greenbook.net/. Registered users can perform advanced searches of either database by various criteria, including trade name, common name, manufacturer, crop tree species, weed species, state, and (only Greenbook^®) by EPA Registration number . Both databases provide extracted important product information in abbreviated format. Greenbook^® allows for side-by-side comparison of up to three products and for setting product E-Alerts. All information contained in the Greenbook^® reference books and CDs is accessible on-line. Registration is currently available free of charge for Greenbook^® at the home page and for CDMS at http://premier.cdms.net/webapls/formsloginRef.asp?/webapls. The latter replaces ChemSearch, which was a paid service of CDMS. One has to keep in mind that, while these and other databases are very useful tools, they cannot be expected to be always completely up-to-date, because of the very rapidly changing herbicide market. CDMS contains a more complete list of forestry herbicides.

Selection of herbicides registered for use in pine management differs from state to state. Only products registered by the Florida Department of Agriculture and Consumer Services (FDACS) can be legally purchased in the state of Florida. The general public can search the FDACS web site at http://www.flpesticide.us or the National Pesticide Information Retrieval System (NPIRS) at http://state.ceris.purdue.edu/ for active Florida registrations. The latter is more user-friendly, can be searched by one of several criteria and provides concise information about each product.

It has to be emphasized that the effectiveness and safety of use of a particular herbicide in a given situation greatly depends on several factors including formulation, pine species, age and stage of growth, weeds to be controlled, and timing, technique and conditions during application. Therefore, one has to refer to the manufacturer's product label for details and consult other literature and qualified professionals regarding the appropriate approach and best products to use. Several publications related to herbicides can be found on the EDIS web site (EDIS - Electronic Data Information Source - UF/IFAS Extension). Another good source of herbicide-related information (including relevant links) is the Pesticide Information Office (PIO) at the University of Florida, IFAS, accessible through http://pested.ifas.ufl.edu. The PIO has the responsibility for assembling, maintaining and disseminating current pesticide information in the state of Florida. County Extension Agents can be contacted at County Extension Offices located throughout the state of Florida (http://solutionsforyourlife.ufl.edu/map/index.html).

References

Carter, D.R. and Jokela, E.J. 2002. Florida's Renewable Forest Resources. CIR 1433. School of Forest Resources and Conservation, Florida Cooperative Extension Service, IFAS, University of Florida, Gainesville, FL., 10 pp. http://edis.ifas.ufl.edu/FR143

CDMS Labels & MSDS. 2008. http://www.cdms.net/LabelsMsds/LMDefault.aspx. (accessed August 12, 2008)

Hodges, A.W., W.D. Mulkey, J.R. Alavalapati, D. R. Carter, and C.F. Kiker. 2005. Economic Impacts of the Forest Industry in Florida, 2003. Final Report to the Florida Forestry Association. University of Florida, Institute of Food and Agricultural Sciences, Food and Resource Economics Department and School of Forest Resources and Conservation. 47 pp. http://edis.ifas.ufl.edu/FE538

National Pesticide Information Retrieval System (NPIRS). 2008. Purdue University. http://state.ceris.purdue.edu/. (accessed August 12, 2008)

Nordby, D.E. and A.G. Hager. Herbicide Formulations and Calculations: Active Ingredient or Acid Equivalent? Weed Fact Sheet. University of Illinois Integrated Pest Management. http://weeds.cropsci.illinois.edu/extension/factsheets/aivsae.pdf. (accessed August 12, 2008)

Pesticide Products Registered in Florida. Online Pesticide Registration System. 2008. Florida Department of Agriculture and Consumer Services. Division of Agricultural Environmental Services. Bureau of Pesticides. http://www.flpesticide.us/. (accessed August 12, 2008)

Tables

The Institute of Food and Agricultural Sciences (IFAS) is an Equal Opportunity Institution authorized to provide research, educational information and other services only to individuals and institutions that function with non-discrimination with respect to race, creed, color, religion, age, disability, sex, sexual orientation, marital status, national origin, political opinions or affiliations. For more information on obtaining other extension publications, contact your county Cooperative Extension service.

U.S. Department of Agriculture, Cooperative Extension Service, University of Florida, IFAS, Florida A. & M. University Cooperative Extension Program, and Boards of County Commissioners Cooperating. Nick T. Place, Dean.

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