FOR Silviculture Forestry Herbicide Facts*

Transcription

1 FOR Silviculture 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 fact sheet is to provide one-page summaries of the most important characteristics of weed-control chemicals used in forestry. The 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 principle ingredient, glyphosphate. 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 name of the active ingredient. Information categories The following information categories are presented for each chemical: Herbicides are foliar active, soil active, or both. This refers to how the chemical enters the plant. Foliar-active chemicals must 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. 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 towards the tips of the branches and leaves. Chemicals transported in the phloem move both up and down the plant. A brief description is given of how the chemical affects plant biochemistry. General classes of plants which are resistant to the effects of the chemical are presented in this section. Environmental Consideration: Information is provided on four key characteristics related to the environment. Refers to a chemical's tendency to go into a gaseous state after application. Indicates whether a chemical is broken down or decomposed by sunlight. Provides the potential for off-site movement through leaching. Indicates the expected time after application that one-half of the chemical *Adapted from: McNabb, K. Forestry herbicide facts. Alabama Extension Service, Auburn University, Alabama ANR-629

2 2 would naturally decompose in the environment. For example, suppose that an application is made of 20 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 is provided in reference to mammals and to fish. LD 50 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 LD 50 = 200 mg/kg (extremely toxic) Aspirin LD 50 = 1,240 mg/kg (moderately toxic) Table salt LD 50 = 3,000 mg/kg (moderately toxic) LC 50 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 an ester (oil soluble) liquid or dry formation. Trade names and manufacturers are also given. Additional sources of information Weed Science Society of America Herbicide Handbook (6 th edition) published by the Weed Science Society of America. Champaign, Illinois. Miller, J.H., and R.J. Mitchell A Manual on Ground Applications of Forestry Herbicides. U.S. Forest Service, Atlanta, Georgia. Management Bulletin R8-MB 21. Table 1. Weed Control Products Used in Forestry PRODUCT Accord Aresenal Applicators Concentrate Banvel Banvel 720 Chopper Escort Garlon 3A Garlon 4 Oust Pronone 10G Tordon K Tordon 101M Tordon 101R Tordon RTU Velpar L Velpar ULW Weedone 2,4-DP ACTIVE INGREDIENT Glyphosphate Imazapyr Dicamba Dicamba 2,4-D Imazapyr Metsulfuron Triclopyr Triclopyr Sulfometuron Hexazinone Picloram 2,4-D picloram 2,4-D picloram 2,4-D picloram Hexazinone Hexazinone Dichlorprop

3 3 2,4-D and 2,4-DP (Dichlorprop) Foliar Translocated in the food transport system Accelerated by disorganized growth Grasses generally resistant Environmental Considerations Related to formulation; volatility can be a problem with Ester formulations, particularly dichlorprop Minimal Not tightly bound to soil, particularly at higher ph levels; Leaching potential in sandy soils 28 days LD mg/kg (moderately toxic) LC ppm (slightly toxic) Product Formulation 40% 2,4-D amine plus 10% picloram 21% 2,4-D amine plus 5% picloram 25% 2,4-D amine plus 13% dicamba Oil and water-soluble Liquid 59% diclorprop Ester Tordon 101M (Dow/Elanco) Tordon 101R and Tordon RTU (Dow/Elanco) Banvel 720 (Sandoz) Weedone 2,4-DP (Rhone Poulenc)

4 4 Dicamba Foliar and soil Translocated in food and water systems Accelerated by disorganized growth Grasses generally resistant Environmental considerations Minimal Some, but insignificant Relatively mobile in soil 14 days LD 50-1,707 mg/kg (moderately toxic) LC ppm (slightly toxic) Product Formulation Banvel (Sandoz) 40% dicamba Water-soluble liquid 13% dicamba plus 25% 2,4-D amine Banvel 720 (Sandoz)

5 5 Environmental Consideration Product Information Water-soluble liquid 41% glyphosphate, no surfactant Glyphosphate Foliar Translocated in food and water systems Amino acid inhibitor Non-selective Negligible Negligible Tightly bound to soil and organic matter 61 dyas LD 50-5,600 mg/kg (slightly toxic) LC ppm (slightly toxic) Accord (Monsanto)

6 6 Environmental Consideration Product Formulation Water-dispersable liquid 25% hexazinone Granular 75% water-soluble Hexazinone Primarily soil-active, some foliar activity Translocated in water-transport system Inhibits photosynthesis Broad spectrum control with some selectivity for conifers Minimal Slow; Reported to be 10% per week Adsorbed by organic matter and clay; Highly water-soluble with potential for leaching on sandy soils 30 days LD 50-1,690 mg/kg (moderately toxic) LC ppm (practically non-toxic) Other - eye irritant Velpar L (Dupont) Velpar ULW (Dupont)

7 7 Imazapyr Foliar and Soil Translocated in food and water systems Inhibits synthesis of specific amino acids Conifers generally resistant Environmental Considerations Negligible Can be significant Adsorbed by soil; leaching usually not a problem 27 days LD 50-5,000 mg/kg (slightly toxic) LC ppm (slightly toxic) Product Formulations Arsenal Applicators Concentrate 54% imazapyr (American Cyanamid) Oil- or water-soluble Liquid 3.6% imazapyr Chopper (American Cyanamid)

8 8 Environmental considerations Product Information Dry flowable 60% metsulfuron methyl Metsulfuron Foliar and Soil Translocates in food and water systems Inhibits cell division and amino acid synthesis Broad spectrum herbicide; some apparent Conifer selectivity Negligible Negligible Low adsorbtion to clay but some adsorbtion to organic matter; solubility increases with increasing ph; some leaching potential but use very low rates 42 days LD 50-5,000 mg/kg (slightly toxic) LC ppm (practically non-toxic) Escort (Dupont)

9 9 Environmental Considerations Product Information Water-soluble liquid 24% picloram Water-soluble liquid 10% picloram plus 40% 2,4-D amine Water-soluble liquid Ready to use 5% picloram plus 21% 2,4-4 amine Picloram Soil and foliar Translocated in food and water systems Accelerated but disorganized growth Broad-spectrum herbicide although most grasses resistant Minimal Reported to photodecompose but actual rates not conclusively measured Some adsorbtion but generally very mobile in soil 63 days LD 50-8,200 mg/kg (slightly toxic) LC 50 - slightly toxic Tordon K (Dow/Elanco) Tordon 101M (Dow/Elanco) Tordon 101R (Dow/Elanco) Tordon RTU (Dow/Elanco)

10 10 Environmental Considerations Product Information Water-dispersable granule 75% sulfometuron-methyl Sulfometuron Soil and foliar Translocated in the food and water systems Stops cell division. Particularly at growing t tips Conifers and other woody perennials resistant Minimal Minimal Mobility increases with higher ph; Adsorbed by soil organic matter 10 days LD 50-5,000 mg/kg (slightly toxic) LC ppm (slightly toxic) Oust (DuPont)

11 11 Environmental Considerations Product Formulation 44% triclopyr amine Water and oil-soluble liquid 62% triclopyr ester Triclopyr Foliar Translocated in the food and water systems Not known exactly, but similar ti 2,4-D and picloram Most grasses tolerant Can be a problem with ester formulations Rapid Not readily leached 46 days LD mg'kg (moderately toxic) LC ppm (practically non-toxic) Garlon 3A (Dow/Elanco) Garlon 4 (Dow/Elanco)