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Printed from the website of the Alabama Cooperative Extension System · http://www.aces.edu
| Forestry Herbicide Facts |
Weed-control chemicals are used in forestry for site preparation before
planting, herbaceous weed control during the first 2 years after planting,
and release of established crop trees from competing woody vegetation. The
purpose of this publication is to provide one-page summaries of the most
important characteristics of weed control chemicals used in forestry. These
summaries should be used for general reference, not as prescriptions or
application guides. Applicators must carefully read the product label before
using any pesticide and must follow all directions, precautions, and restrictions.
The herbicides are listed in alphabetical order by their common names. For example, the formulation widely known as Roundup is listed under the common name of its principal active ingredient, glyphosate. While common names are sometimes not as well known as trade names, it is the active ingredient that has the greatest influence on the behavior and properties of the product. Also, organizing by common names eliminates repetition.
To assist you in finding information when you know only the trade name, Table 1 lists the trade name with the corresponding common name of the active ingredient. Included are links to the summaries given in this publication.
The following information categories are presented for each chemical:
Activity. Herbicides are either foliar active, soil active, or both. This refers to how the chemical enters the plant. Foliar-active chemicals must usually have adequate leaf surface area in order to be absorbed by the plant, but in some cases foliar-active chemicals can be applied directly to the stem. Soil-active chemicals are pulled into the plant through the roots as they take up water and transpire.
Movement in Plants. Chemicals are translocated in the food transport system of the plant (the phloem) or in the water transport system (the xylem) or in both. Chemicals transported in the xylem are characteristically soil-active and move with the transpiration flow--from the base of the tree toward the tips of branches and leaves. Chemicals transported in the phloem move both up and down the plant.
Mode of Action. A brief description is given of how the chemical affects plant biochemistry.
Selectivity. General classes of plants which are resistant to the effects of the chemical are presented in this section.
Environmental Considerations. Information is provided on four key characteristics related to the environment:
Volatility--Refers to a chemical's tendency to go into a gaseous state after application.
Photo decomposition--Indicates whether a chemical is broken down or decomposed by sunlight.
Mobility in Soil--Provides the potential for off-site movement through leaching.
Half-life--Indicates the expected time after application that one-half of the chemical would naturally decompose in the environment. For example, suppose that an application is made of 2 pounds of an active ingredient with a half-life of 30 days. One month after application, 1 pound of the chemical would have decomposed and 1 pound would still be present.
Toxicity. Toxicity is provided in reference to mammals and to fish. LD50 is the lethal dose of a chemical required to kill 50 percent of a test-animal (rat) population. It is expressed in milligrams of chemical for each kilogram of test-animal weight. For reasons of comparison, the following toxicities are provided:
Caffeine LD50 = 200 mg/kg (extremely toxic)
Aspirin LD50 = 1,240 mg/kg (moderately toxic)
Table salt LD50 = 3,000 mg/kg (moderately toxic)
LC50 is the lethal concentration in water at which a chemical becomes lethal to 50 percent of a test population of fish.
Product Formulation. Active ingredients are often sold under one or more formulations. This section provides the percentage of the active ingredient and indicates whether it is an amine (water soluble) or ester (oil soluble) liquid or a dry formulation. Trade names and manufacturers are also given.
| Product | Active Ingredient |
| Aatrex 4L | atrazine |
| Aatrex 80W | atrazine |
| Aatrex Nine-O | atrazine |
| Access | picloram & triclopyr |
| Accord | glyphosate |
| Arsenal Applicators Concentrate | imazapyr |
| Atrazine 4L | atrazine |
| Banvel | dicamba |
| Banvel 720 | 2,4-D & dicamba |
| Banvel CST | dicamba |
| Chopper | imazapyr |
| Escort | metsulfuron |
| Fusilade 2000 | fluazifop |
| Garlon 3A | triclopyr |
| Garlon 4 | triclopyr |
| Oust | sulfometuron |
| Poast | sethoxydim |
| Pronone MG | hexazinone |
| Pronone 10G | hexazinone |
| Pronone 25G | hexazinone |
| Pronone Power Pellet | hexazinone |
| Roundup | glyphosate |
| Tordon K | picloram |
| Tordon 101M | 2,4-D & picloram |
| Tordon 101R | 2,4-D & picloram |
| Tordon RTU | 2,4-D & picloram |
| Velpar L | hexazinone |
| Velpar ULW | hexazinone |
| Weedone 2,4-DP | dichlorprop |
| Weedone 170 | dichlorprop |
| Activity | Primarily soil, some foliar activity |
| Movement in plants | Translocated in water transport system |
| Mode of action | Photosynthesis inhibitor |
| Selectivity | Broad spectrum broadleaf and grass control; minimally effective on established weeds; used as a preemergent or early postemergent |
| Environmental Considerations | |
| Volatility | Negligible |
| Photodecomposition | Negligible |
| Mobility in soil | Highly water-soluble but readily adsorbed by organic matter and clay; potential for leaching on sandy soils |
| Half-life | Specific number not available; relatively long-lived |
| Toxicity | LD50 - 3,080 mg/kg (moderately toxic) LC50 - slightly toxic |
| Product Formulation | Trade Name and Manufacturer |
| Water-soluble liquid 43 percent atrazine | Atrazine 4L (Dupont) Aatrex 4L (Ciba Geigy) |
| Wettable powder 80 percent atrazine | Aatrex 80W (Ciba Geigy) |
| Water-dispersible granules 90 percent atrazine | Aatrex Nine-O (Ciba-Geigy) |
2,4-D and 2,4-DP (Dichlorprop) | |
| Activity | Foliar |
| Movement in plants | Translocated in the food transport system |
| Mode of action | Accelerated but disorganized growth |
| Selectivity | Grasses generally resistant |
| Environmental Considerations | |
| Volatility | Related to formulation; volatility can be a problem with ester formulations, particularly dichlorprop |
| Photodecomposition | Minimal |
| Mobility in soil | Not tightly bound to soil, particularly at higher pH levels; leaching potential in sandy soils |
| Half-life | 28 days |
| Toxicity | LD50 - 375 mg/kg (moderately toxic) LC50 - 100 ppm (slightly toxic) |
| Product Formulation | Trade Name and Manufacturer |
| Water-soluble liquid 40 percent 2,4-D amine plus 10 percent picloram |
Tordon 101M (Dow/Elanco) |
| Water-soluble liquid 21 percent 2,4-D amine plus 5 percent picloram |
Tordon 101R and Tordon RTU (Dow/Elanco) |
| Water-soluble liquid 25 percent 2,4-D amine plus 13 percent dicamba |
Banvel 720 (Sandoz) |
| Oil- and water-soluble liquid 30 percent 2,4-D plus 30 percent diclorprop |
Weedone 170 (Rhone Poulenc) |
| Oil- and water-soluble liquid 59 percent diclorprop ester |
Weedone 2,4-DP (Rhone Poulenc) |
Dicamba | |
| Activity | Foliar and soil |
| Movement in plants | Translocated in food and water systems |
| Mode of action | Accelerated but disorganized growth |
| Selectivity | Grasses generally resistant |
| Environmental Considerations | |
| Volatility | Minimal |
| Photodecomposition | Some, but insignificant |
| Mobility in soil | Relatively mobile in soil |
| Half-life | 14 days |
| Toxicity | LD50 - 1,707 mg/kg (moderately toxic) LC50 - 35 ppm (slightly toxic) |
| Product Formulation | Trade Name and Manufacturer |
| Water-soluble liquid 40 percent dicamba |
Banvel (Sandoz) |
| Water-soluble liquid 13 percent dicamba plus 25 percent 2,4-D amine |
Banvel 720 (Sandoz) |
| Ready-to-use water-based liquid 13 percent dicamba |
Banvel CST (Sandoz) |
Fluazifop | |
| Activity | Foliar |
| Movement in plants | Translocated in food and water systems |
| Mode of action | Cell membrane disruption |
| Selectivity | Grass herbicide; broadleaf and woody plants highly resistant |
| Environmental Considerations | |
| Volatility | Minimal |
| Photodecomposition | Minimal |
| Mobility in soil | Low mobility in soil |
| Half-life | 21 days |
| Toxicity | LD50 - 4,096 mg/kg (moderately toxic) LC50 - 5.4 ppm (moderately toxic) |
| Product Formulation | Trade Name and Manufacturer |
| Oil- and water-soluble liquid 13 percent fluazifop-p-butyl |
Fusilade 2000 (ICI Americas) |
Glyphosate | |
| Activity | Foliar |
| Movement in plants | Translocated in food and water systems |
| Mode of action | Amino acid inhibitor |
| Selectivity | Non-selective |
| Environmental Considerations | |
| Volatility | Negligible |
| Photodecomposition | Negligible |
| Mobility in soil | Tightly bound to soil and organic matter |
| Half-life | 61 days |
| Toxicity | LD50 - 5,600 mg/kg (slightly toxic) LC50 - 86 ppm (slightly toxic) |
| Product Formulation | Trade Name and Manufacturer |
| Water-soluble liquid 41 percent glyphosate plus surfactant |
Roundup (Monsanto) |
| Water-soluble liquid 41 percent glyphosate, no surfactant |
Accord (Monsanto) |
Hexazinone | |
| Activity | Primarily soil-active; some foliar activity |
| Movement in plants | Translocated in the water transport system |
| Mode of action | Inhibits photosynthesis |
| Selectivity | Broad spectrum control with some selectivity for conifers |
| Environmental Considerations | |
| Volatility | Minimal |
| Photodecomposition | Slow; reported to be 10 percent per week |
| Mobility in soil | Adsorbed by organic matter and clay; highly water-soluble with potential for leaching on sandy soils |
| Half-life | 30 days |
| Toxicity | LD50 - 1,690 mg/kg (moderately toxic) LC50 - 274 ppm (practically non-toxic) other - eye irritant |
| Product Formulations | Trade Name and Manufacturer |
| Water-dispersable liquid 25 percent hexazinone |
Velpar L (Dupont) |
| Granular 75 percent water-soluble 10 percent clay granule 10 percent clay granule 25 percent water-soluble tablet 75 percent water-soluble tablet |
Velpar ULW (Dupont) Pronone MG (Proserve) Pronone 10G (Proserve) Pronone 25G (Proserve) Pronone Power Pellet (Proserve) |
Imazapyr | |
| Activity | Foliar and soil |
| Movement in plants | Translocated in food and water systems |
| Mode of action | Inhibits the synthesis of specific amino acids |
| Selectivity | Conifers generally resistant |
| Environmental Considerations | |
| Volatility | Negligible |
| Photodecomposition | Can be significant |
| Mobility in soil | Adsorbed by soil; leaching usually not a problem |
| Half-life | 27 days |
| Toxicity | LD50 - 5,000 mg/kg (slightly toxic) LC50 - 100 ppm (slightly toxic) |
| Product Formulations | Trade Name and Manufacturer |
| Water-soluble liquid 54 percent imazapyr |
Arsenal Applicators Concentrate (American Cyanamid) |
| Oil- or water-soluble liquid 3.6 percent imazapyr |
Chopper (American Cyanamid) |
Metsulfuron | |
| Activity | Foliar and soil |
| Movement in plants | Translocates in the food and water systems |
| Mode of action | Inhibits cell division and amino acid synthesis |
| Selectivity | Broad spectrum herbicide; some apparent conifer selectivity |
| Environmental Considerations | |
| Volatility | Negligible |
| Photodecomposition | Negligible |
| Mobility in soil | Low adsorption to clay but some adsorption to organic matter; solubility increases with increasing pH; some leaching potential but use rates very low |
| Half-life | 42 days |
| Toxicity | LD50 - 5,000 mg/kg (slightly toxic) LC50 - 150 ppm (practically non-toxic) |
| Product Formulation | Trade Name and Manufacturer |
| Dry flowable 60 percent metsulfuron methyl |
Escort (Dupont) |
Picloram | |
| Activity | Soil and foliar |
| Movement in plants | Translocated in food and water systems |
| Mode of action | Accelerated but disorganized growth |
| Selectivity | Broad-spectrum herbicide although most grasses resistant |
| Environmental Considerations | |
| Volatility | Minimal |
| Photodecomposition | Reported to photodecompose but actual rates not conclusively measured |
| Mobility in soil | Some adsorption but generally very mobile in soil |
| Half-life | 63 days |
| Toxicity | LD50 - 8,200 mg/kg (slightly toxic) LC50 - slightly toxic |
| Product Formulation | Trade Name and Manufacturer |
| Water-soluble liquid 24 percent picloram |
Tordon K (Dow/Elanco) |
| Water-soluble liquid 10 percent picloram plus 40 percent 2,4-D amine |
Tordon 101M (Dow/Elanco) |
| Water-soluble liquid, ready to use 5 percent picloram plus 21 percent 2,4-D amine |
Tordon 101R (Dow/ELanco) Tordon RTU (Dow/Elanco) |
| Water- and oil-soluble liquid 17.0 percent picloram plus 32.5 percent triclopyr |
Access (Dow/Elanco) |
Sethoxydim | |
| Activity | Foliar |
| Movement in plants | Translocated in the food transport system |
| Mode of action | Inhibits cell membrane synthesis |
| Selectivity | Grass herbicide; broadleaf and woody plants resistant |
| Environmental Considerations | |
| Volatility | Minimal |
| Photodecomposition | Can be significant |
| Mobility in soil | Readily adsorbed by organic matter; low soil mobility |
| Half-life | 11 days |
| Toxicity | LD50 - 2,676 mg/kg (moderately toxic) LC50 - slightly toxic Other - eye irritant |
| Product Formulation | Trade Name and Manufacturer |
| Water-soluble liquid 18 percent sethoxydim |
Poast (BASF) |
Sulfometuron | |
| Activity | Soil and foliar |
| Movement in plants | Translocates in the food and water systems |
| Mode of action | Stops cell division, particularly at growing tips |
| Selectivity | Conifers and other woody perennials resistant |
| Environmental Considerations | |
| Volatility | Minimal |
| Photodecomposition | Minimal |
| Mobility in soil | Mobility increases with higher pH; adsorbed by soil organic matter |
| Half-life | 10 days |
| Toxicity | LD50 - 5,000 mg/kg (slightly toxic) LC50 - 12.5 ppm (slightly toxic) |
| Product Formulation | Trade Name and Manufacturer |
| Water-dispersable granule 75 percent sulfometuron-methyl |
Oust (Dupont) |
Triclopyr | |
| Activity | Foliar |
| Movement in plants | Translocated in the water and food systems |
| Mode of action | Not known exactly, but similar to 2,4-D and picloram |
| Selectivity | Most grasses tolerant |
| Environmental Considerations | |
| Volatility | Can be a problem with ester formulations |
| Photodecomposition | Rapid |
| Mobility in soil | Not readily leached |
| Half-life | 46 days |
| Toxicity | LD50 - 713 mg/kg (moderately toxic) LC50 - 117 ppm (practically non-toxic) |
| Product Formulation | Trade Name and Manufacturer |
| Water-soluble liquid 44 percent triclopyr amine |
Garlon 3A (Dow/Elanco) |
| Water- and oil-soluble liquid 62 percent triclopyr ester |
Garlon 4 (Dow/Elanco) |
| Water- and oil-soluble liquid 32.5 percent triclopyr ester and 17.0 percent picloram ester |
Access (Dow/Elanco) |
Weed Science Society of America. 1989. Herbicide Handbook (6th edition) published by the Weed Science Society of America, Champaign, Illinois.
Miller, J.H. and R.J. Mitchell. 1988. A Manual on Ground Applications of Forestry Herbicides. U.S. Forest Service, Atlanta, Georgia. Management Bulletin R8-MB 21.
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