HERBICIDES Flashcards
Herbicides
Are chemicals that kill plants, specifically, weed species..
Timing and Application Method
Pre-Plant Incorporation: Mechanically mixed into the soil.
Pre-Emergence: Irrigated or Sprayed
Post-Emergence: Irrigated or Sprayed
Pre-Harvest/Post Harvest
Broadleaf vs. Grass
Herbicides tend to either target monocotyledons (grasses) or dicotyledons (broadleaf plants).
Selective vs. Non-selective
Selective herbicides tend to target specific types of plants such as broadleaf or grass weeds. Also refers to herbicides that attack weeds though leave the desired crop unscathed.
Non-selective herbicides kill all types of vegetation.
Due to this outcome, these are usually applied early on or even before planting the desired crop.
Contact vs. Translocated
Similar to contact and systemic.
Contact herbicides only affect the tissues that have been sprayed.
Translocated herbicides are absorbed through either the roots or stomata of the plant. From here the active compound continues entering the plant through the xylem and the phloem affecting it through its’ entirety.
Persistence
Herbicide persistence varies substantially depending on soil type and chemical being applied.
Many herbicides are designed to remain toxic for up to several weeks or even months after application to provide extended weed control.
Considerations if the herbicide residue does not break down before the crop is planted on the treated area.
Also worthwhile noting that the active compounds are not accumulating in the groundwater.
Mammalian Toxicity
Most herbicides have low acute mammalian toxicity. However, there are exceptions such a paraquat.
For these exceptions, the herbicides tend to be placed on the restricted use list.
Environmental Concerns
The California Department of Pesticide Regulation’s Ground Water Protection program may restrict the application of certain herbicides in some areas where leaching is of concern.
Runoff, volatilization, and drift must be considered when selecting herbicide materials.
