Vegetation Control

Tim Prather
March 2022

Total vegetation control with soil-residual herbicides is a process in which the addition of chemicals renders the soil unfit for plant growth. Soil-residual herbicides do not kill all animal and microbiological life in the soil.

Keep the following in mind when using soil-residual herbicides:

  1. Identify the weeds that are to be controlled.
  2. Know the area where the chemicals are to be used. Adjacent vegetation and terrain are important.
  3. Develop a management plan. No single herbicide or other weed control practice will solve all weed problems.
  4. Follow precautions when using soil-residual herbicides.
  5. Prevent people, animals, and equipment from moving soil away from treated area.Avoid spray drift during application.
  6. Avoid applying residuals where wind or water might move the treated soil.
  7. Some herbicides vaporize easily. Reduce hazard by applying at lower temperatures and use low-volatile formulations.
  8. Do not apply where roots of desirable vegetation may extend into treated area.
  9. Some herbicides are poisonous to animals. Do not apply these to vegetation, fruit, or seed that might be eaten.
  10. Apply soil-residual herbicides during late fall east of the Cascades to allow winter precipitation to move the herbicide into the soil. In the high-rainfall areas west of the Cascades, apply after the heavy winter rainy season but early enough to ensure adequate moisture to move the herbicide into the soil.
  11. Ensure that these herbicides do not enter sources of irrigation water; some crops are extremely sensitive to some of these herbicides. Severe crop losses have been due to irrigation water contamination. Only use these herbicides on banks, canals, and streams if the label specifically allows that use.

Note Information in this handbook is not intended to be a complete guide to herbicide use. Before using any chemical, read the label recommendations on the container. Before a chemical can be recommended for a specific use, it must be thoroughly tested. Following the recommendation on the manufacturer’s label can prevent many problems from the improper use of a chemical.