Herbicide, a Brief Overview. Cody Miller, The Nature Conservancy

Transcription

1 Herbicide, a Brief Overview Cody Miller, The Nature Conservancy

2 What is a herbicide? Chemicals used for killing plants or severely interrupting their normal growth processes (WSSA).

3 Herbicides Restricted or regulated based on application site. Target specific processes unique to plants (photosynthesis, enzymes, etc.) - modes of action Target species groups Natural areas are not their target audience

4 Oh, No Herbicides! Wide margin of safety between exposure levels that are toxic to plants and potential exposure levels to people Mammalian toxicity usually very low Higher toxicity for fish and amphibians

5 Toxicity, Exposure, and Hazard Toxicity is a measure of the ability to cause harmful effects Exposure is contact or dose (oral, inhalation, dermal, ocular) Hazard is the risk of harmful effects Hazard = Toxicity x Exposure The hazard is in the dose

6 LD 50 Lethal DoseLD 50 /LC 50 : A common measure of acute toxicity is the lethal dose (LD 50 ) or lethal concentration (LC 50 ) that causes death (resulting from a single or limited exposure) in 50 percent of the treated animals. LD 50 is generally expressed as the dose in milligrams (mg) of chemical per kilogram (kg) of body weight. LC 50 is often expressed as mg of chemical per volume (e.g., liter (L)) of medium (i.e., air or water) the organism is exposed to. Chemicals are considered highly toxic when the LD 50 /LC 50 is small and practically non-toxic when the value is large. However, the LD 50 /LC 50 does not reflect any effects from long-term exposure (i.e., cancer, birth defects or reproductive toxicity) that may occur at levels below those that cause death. Dosage (mg/kg body weight) required to kill 50% of the test population Acute toxicity testing

7 Relative Acute Oral LD 50 Toxicities Nicotine Caffeine 2,4-D Aspirin Garlon 4 Vitamin A Garlon 3A Table salt Rodeo, Roundup Pro, Arsenal, Escort, Stalker 1 mg/kg 192 mg/kg 699 mg/kg 1000 mg/kg (~ 3 oz/185 lbs) 1581 mg/kg 2000 mg/kg 2574 mg/kg 4000 mg/kg >5000 mg/kg

8 Label Signalword Refers to handling product concentrate Determined by acute toxicity testing (oral, inhalation, dermal, ocular) Drives label precautionary statements and PPE Caution Warning Danger Danger Poison

9 Persistence Length of time a herbicide remains in the environment Chemistry and environmental conditions Soil half-life Time required for ½ of compound to degrade 10 days (2,4-D) to 142 days (imazapyr)

10 Herbicide Degradation Herbicides can be broken down in the environment by several processes: Sunlight (photolysis) Water (hydrolysis) Chemical reactions Microbial (bacteria, fungi, etc.) End products are H 2 O, CO 2, and elemental forms

11 Herbicide Formulations (Delivering the Active Ingredient) Trade name: Aqua Star Common name/ Active ingredient: Glyphosate (5.4 lbs ai/gal IPA salt of glyphosate) 53.8% Acid equivalency (4.0 lbs ae/gal glyphosate) Other ingredients: 46.2% Salts/amines Water soluble Oil insoluble Esters Oil soluble Water emulsifiable Dry Formulations

12 Read the Herbicide Label Product information Product name Active ingredient/ common name EPA Reg. No. Precautionary statements Signal words Personal Protective Equipment

13 Read the Herbicide Label Directions for use Storage and Disposal Application Equipment and Techniques application rates General information General use precautions Control Species Drift Agricultural Use and Restrictions Restrictions Warranty Disclaimer Approved uses

14 DOW AGROSCIENCES CONFIDENTIAL - Do not share without permission

15 The Label is the Law Using Herbicides at concentrations above the recommended rate is illegal

16 Glyphosate (Rodeo, Roundup, etc.) EPSP enzyme inhibitor prevents production of key amino acids Non-selective Uptake: Foliar/shoot Soil activity: None Translocation: Phloem Applications: Cut surface, foliar Soil half-life: 47 days Degradation: Microbial (soil and water)

17 Imazapyr (arsenal, chopper, etc. ) ALS inhibitor Non-selective Uptake: plant tissue and roots Soil activity: High Translocation: Phloem and Xylems Applications: Cut surface, foliar or basal bark Soil half-life: days Degradation: slow microbial and photolysis

18 Triclopyr (Garlon 3A and Garlon 4) Growth regulator mimics natural plant hormones, disrupts cell division Selective; some warm season grasses sensitive Uptake: Foliar/shoot, root very limited Soil activity: Very limited Translocation: Phloem Applications: Basal, cut surface, foliar Soil half-life: days Degradation: Microbial (soil), photolysis (light) and hydrolysis (water)

19 Adaptive Management and Herbicide Selection

20 Cogon Grass (Imperata Which herbicide do you choose? Imazapyr Imazapyr/glyphosate Glyphosate Other considerations T&E Species Land Use/Public Access Water Levels Time Constraints cylindrica)

21 The Toolbox Herbicides Mechanical removal Manual removal Biological Control Rx Fire Grazing EDRR? Plant ID training? Funding Public awareness? Decontamination?

22 Species Considerations Type of weed Broadleaf herb Hardwood Vine Grass Sedge Is it aquatic? Life Cycle Annual ( 1 year) Biennial (2 years) Perennial (? Years)

23 Herbicide Selection Effectiveness against the target species -do you know what is effect for this species? Mechanisms of dissipation Behavior in the environment Toxicity to mammals, birds, fish, amphibians or other non target species Human Safety and exposure Application site considerations

24 Application Site Considerations Threatened & Endangered Species Herbicide sensitivity in priority native species Land use Public access Water levels Time constraints

25 Water Levels Torpedo Grass(Panicum repens) Imazapyr Do not apply within 1 mile upstream of active irrigation water intake Do not apply within 1/2 mile upstream of functioning potable water intake 120 day waiting period for irrigation purposes Glyphosate(Aquatic) No Downstream considerations

26 Threatened and Endangered Species Central Highlands with Natal Grass entwined with Warea carteri, Carter s Mustard Hand pulling is ineffective Physical Barriers to prevent drift Do Nothing Clipping seed heads that are to close in proximity to be sprayed

27 Public Access and Land Use Velpar vs RoundUp 48 hr 4hr re-entry interval 30 days 3-5d grazing restriction

28 Wind Drift potential is lowest between 2-10 mph Florida YRS JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC ANN APALACHICOLA DAYTONA BEACH < 2 mph higher drift potential because of variable winds and potential for inversion FORT MYERS GAINESVILLE JACKSONVILLE KEY WEST MIAMI Reduce off-target damage via larger droplet size and lower pressure ORLANDO PENSACOLA TALLAHASSEE TAMPA VERO BEACH WEST PALM BEACH

29 Temperature Application between 65F and 85F Lakeland Station: Lakeland County: Polk COOP ID Number: <65F slows the translocation of herbicide throughout the plant >85F herbicide can become volatile leading to drift and lower kill rate Temperature Normals Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Annual Max Mean Min

30 Rainfast Rainfast- The herbicide has adequately dried or has been absorbed by plant tissues to still be effective after rainfall. Polaris(Imazapyr)- 1 hour Rodeo/Roundup Pro(Glyphosate)- 30 minutes Milestone- 2 hrs. Plateau- 1 hr. Garlon 3A/4(Triclopyr)- 2 hrs. Velpar- Needs minimum ¼ within 2 weeks of application

31 Cogon Grass (Imperata Which herbicide do you choose? Imazapyr Imazapyr/glyphosate Glyphosate Other considerations T&E Species Land Use/Public Access Water Levels Time Constraints cylindrica)

32 Tu, M., Hurd, C., & J.M. Randall, Weed Control Methods Handbook, The Nature Conservancy, Version: April The Center for Invasive Species and Ecosystem Health National Pesticide Information Center Florida State University, Florida Climate Center