Rangeland exam 2(IPM-Herbicides)

pesticides

Any chemical used to “control” some
living substance
◦Insecticide
◦Rodenticide
◦Fungicide
◦Herbicide

The herbicide must

• contact plant when the plant is
  susceptible

• remain in contact long enough
  to be absorbed

• reach a living cellular site at a
  concentration sufficient (toxicity)
  to disrupt a vital process or
  damage vital structures to kill the
  plant.

Why Choose Herbicide?

1. Can be a cost effective approach

2. Terrain has very little impact

3. can provide selective control

4. Good for releasing in situ desirable plants

5. Low labor requirements

6. generally safe when following safegaurds

maybe don’t choose herbicides?

1. Requires extended timing and rates

2. may effect non-targeted, desirable plants

3. may increase plant toxicity

4. Social/economic concerns about pesticides

5. potential danger to applicator or enviroment

6. unknown or dangerous health hazards

Growth Regulation

Chemical mimics auxin, a plant hormone that regulates
growth and development (e.g., cell development, protein
synthesis, respiration)

◦ Most widely used group of herbicides on rangelands
◦ Selective against broad leaf plants
◦ Most can be foliar (leaf uptake) or soil (root uptake) applied

Amino Acid Synthesis
Inhibitors

Prevent key amino acid synthesis

◦ Blocks protein and enzyme production
◦ Slow acting but effective

Photosynthesis
Inhibitors

• Blocks photosynthesis

• Build-up of free radicals destroys cell membranes

• Mostly used for perennial weeds

• Often long soil residence

• Prevents underground shoot and sprout production

Aerial Application Method Advantages

• Faster coverage over large areas

• Terrain doesn’t matter

• Lower cost per acre on large areas

• No mechanical disturbance
  of soils or vegetation

Aerial Application Method Disadvantages

• More expensive

• Requires specialized equipment

• Susceptible to weather (e.g., wind and fog)

• Drift from direct target areas very possible

Ground Application Method (Advantages)

• Adapted to small acreages

• Less drift

• Fewer climate limitations

• No runways or launch pads required

• Applicator safety often higher

Ground Application: Disadvantage

Problem: desirable plants
in understory may be
susceptible to herbicides
that control salt cedar.

Individual Plant Treatment

• Common on small scale: portable sprayers

• Targeted efforts of species of interest

• Different parts of a plant can
  be targeted