Lecture 4 - Chemical Treatments of Rangelands

Advantages for Chemical Control:

1. Can be Inexpensive

2. Application not limited by terrain

3. Easily ranges from individual plant treatment to area-wide treatment

4. Can be very selective

5. Maintains other vegetation cover

6. Low soil disturbance

Disadvantages for Chemical Control:

1. Some pest plants are not well controlled by chemicals

2. No seedbed preparation (may make seeding difficult)

3. May kill desirable plants

4. May increase toxicity of some poisonous plants

5. May be hazardous to applicator/wildlife/public

6. Not all health hazards may be known

7. Social Stigma

_______: Any chemical used to kill or control plants

Herbicide

______: Active ingredient is in a liquid carrier

examples:

• Solution

• Emulsion

• Suspension/Flowables

Liquid Formulation

_______: Active ingredient is on the surface of a solid carrier

examples:

• Wettable Powder

• Dry Flowable

• Granules/Pellets

Dry Formulation

_______: Applied before the target weed germinates and emerges, they act on the roots or shoots of newly germinated seeds.

Pre-emergent Herbicide

______: Applied to the foliage of the target weed after it has emerged from the soil.

Post-emergent Herbicide

_______: Causes local injury only to plant parts directly contacted

Contact Herbicide

_______: Applied to one part of a plant but is spread by the plant throughout the plant

Translocated (Systemic) Herbicide

_______: An herbicide that kills or damages only a particular species or group of species, with little or no injury to other species

Selective Herbicide

Nonselective Herbicide

________: An herbicide which kills or injures all plant species to which it is applied

________: An herbicide that kills or damages plants when applied to the soil

Soil-active Herbicide

Herbicide efficacy depends on:

• Surface Contact

• Penetration

• Translocation

• Disruption of Vital Function

• Active plant growth/photosynthesizing

Ultimately, these are reliant on:

Active plant growth/photosynthesizing

Environmental conditions

Classifying Rangeland Herbicides

Application Method

Selectivity (type of plant affected)

Mode of action

Soil Residual Activity

Toxicity

Chemical Family

Application Targets:

Foliage

Soil

Both

Stem

Selectivity:

Selective

Non-selective (general)

Partially selective

Modes of Action:

Target critical chemical and physiological systems in plants

Important Modes of Action:

Synthetic Auxin

Photosystem II Inhibition

ESPS Synthase Inhibition

Membrane Disruptor

________: uncontrolled, unsustainable growth… the plant literally grows to death (2,4-D)

Synthetic Auxin

Photosystem II Inhibition

_______: stops photosynthesis by binding to plastiquinone enzyme and blocking electron transport (atrazine)

EPSP Synthase Inhibition

_____: blocks an enzyme (epsp) that synthesizes amino acids (glyphosate)

Membrane Disruptor

_______: takes an electron from the ps I electron chain, thereby stopping photosynthesis (paraquat)

Methods of Herbicide Application:

Foliage Spray

Individual Stem/Trunk Treatment

Soil Application

Advantages of Boom Application

More even distribution of spray

Less drift/wind problems

Advantages of Boomless Application

Less expensive equipment

Easier maneuvering

Convenient for brush, fence, rough terrain

Less nozzle stoppage

Advantages of Ground Application

Better over small acreages

No landing strip required!

Less drifting in fog or wind

Lower equipment costs

Safer for applicator

Advantages of Aerial Application

Faster Coverage

Possible over wet or rough terrain

Lower cost per acre on larger acres

No soil disturbance

Better coverage of tall, dense brush

Advantages of Fixed Wing Application

Greater lifting power in thin, warm air

Greater payload

Cheaper on large projects

More available

Advantages of Helicopter Application

No landing strip required

Less troubled by trees/snags and steep terrain

Slower airspeed and maneuverability results in greater accuracy

_______: Trunk base spray

Frill/Notch/Girdle Spray

Streamline Spray

Cut-stump Spray

Trunk Injection

Stem/Trunk Treatments

_______: Soil Injection

Stem/Base Placement

Pattern (bands/grids) Placement

Soil Application

Advantages of Soil Active Herbicides

Reduced (no?) drift

No foliage interception

Controlled release possible

Easier handling and application

Generally pre-mixed

Often has longer residual activity

Disadvantages of Soil Active Herbicides

More expensive to make, package and ship

May be less effective than the same liquid chemical

More expensive per unit of killing power

May be moved by surface winds or water movement

Needs rainfall to activate

Environmental Conditions that Influence Herbicide Effectiveness:

1. Temperature

2. Precipitation/Rainfall

3. Humidity

4. Wind

5. Light

6. Soil Moisture

7. Other Soil Factors (texture, OM content, etc)

______: the herbicidal preparation by the manufacturer, including the kind, chemical and physical form, and concentration of the toxicant, along with other ingredients

Formulation AKA Commercial Product

_______: The chemical agent that causes the toxic effect on plants

Toxicant

_________: The substance that with which the commercial product is mixed for more effective application– may be liquid, solid or gas

Carrier

_______: The commercial product, carrier, and surfactant mixed together and ready to be sprayed

Spray mix

________: A spray mixture in which the toxicant is mixed in ionic form with the carrier

Solution

________: A spray mixture in which the liquid toxicant is dispersed as globules in a liquid carrier (oil in water)

Emulsion

________: A spray mixture in which the toxicant in aqueous form is dispensed in an oil carrier (requires special application equipment)

Invert Emulsion

_________: A spray mixture in which the solid, finely particulate toxicant is dispersed in a liquid carrier

Suspension

________: An addition to the spray mix (or commercial product) that increases the spreading, wetting, sticking, solubility, etc of the mix

Surfactant

________: The part of the commercial product or spray mix that directly causes the herbicidal effects

Active Ingredient (A.I.)

_________: The amount of active ingredient, expressed in terms of the parent acid

Acid Equivalent (a.e.)

Herbicide Rate Prescriptions Come in 3 forms:

Lbs a.i/a.e. per acre

Lbs a.i/a.e. per 100gal

Weight/volume of commercial product per plant or acre

_______: The oral dosage that kills 50% of test animals, expressed as mg/kg of body wt.

LD50

_______: “No Observable Effect Limit” or “No Observable Adverse Effect Limit” = the highest level that causes no adverse effect in the most sensitive animal species tested.

NOEL / NOAEL

______: “Margin of Safety” = NOEL/Dose…

MOS is considered high risk when <100

MOS

________: Indicates the relative toxicity of a chemical

Toxicity Class

Federal Insecticide, Fungicide, and Rodenticide Act

Original law passed in 1947

• Gave authority for regulating pesticides to Department of Ag

Revised law passed in 1972

• Moved regulatory authority to EPA

• Amendments in 1988 and 1996

Requires that pesticides be REGISTERED and sold under an approved LABEL

FIRFA

Registration Categories

1. General Use (anyone can purchase and use)

2. Restricted Use (Requires application by a certified applicator)

• Dangerous to the Environment

• Dangerous to the Applicator

3. Experimental Use

• Allow manufacturers to field test pesticides under experimental use permits

4. Emergency Use

__________: Administered by Texas Department of Agriculture

“Private Applicator” or “Commercial Applicator” licenses

Allows purchase and use of “restricted” herbicides

Herbicide Applicator’s License

Herbicide Labels

1. Define active ingredients and concentrations

2. Include Toxicity Signal Words

3. Describe Registration restrictions

4. Precautionary Statement/Handling

5. Physical and Chemical hazards for storage

6. Environmental Hazards

7. Directions and Rates for Use

8. Storage and Disposal Precautions

Herbicide Label - Questions to Ask

1. What is the active ingredient and concentration?

2. What is the Toxicity Class?

3. Are there any Registration restrictions?

4. What precautions are required for Handling?

5. What are the Physical and Chemical hazards for storage?

6. What are the Environmental Hazards?

7. What/Where are the Directions and Rates for Use?

8. What are the Storage and Disposal Precautions?