Herbicide Formulations and Application Equipment

Herbicides for use in home lawns are available in several formulations. Generally there are two main types: granular- to be applied in a dry form using fertilizer-type spreaders, and liquids- powders or wettable granules formulated to be mixed with water and applied as a spray.

Granular

Granular herbicides are the most convenient and easiest to use. Many preemergence herbicides are marketed as granular formulations. These products may also be available in combination with granular fertilizers.

Fertilizer/herbicide combinations have several advantages:

  1. Convenient, saving one additional trip over the lawn.
  2. Can be conveniently applied with a common fertilizer spreader (no specialized equipment needed).
  3. Spray drift is avoided that may occur with foliar spray.
  4. The fertilizer may stimulate lawngrass growth and may reduce any 'stunting' effect of the herbicide.

Fertilizer/herbicide combinations have several common misuses and disadvantages:

  1. Fertility rate, especially with nitrogen, may be too high, depending on lawngrass type and time of year.
  2. Use around or underneath trees and shrubs that are not tolerant of the herbicide.
  3. An additional pass around or underneath trees and shrubs to give them extra fertilizer, resulting in herbicide overdose that can injure or kill trees and shrubs.
  4. More expensive than products used separately.
  5. Fertilizer/herbicide combinations containing postemergence broadleaf herbicides (like 2,4-D and dicamba) applied preemergence are less effective than foliar sprays. Also, these products may injure desirable plants by root uptake.

Liquids

Most postemergence and some preemergence herbicides are sold in formulations meant to be mixed with water and applied as liquids. The actual product may be in a solid form, such as a powder or water-dispensible granule that mixes well with water. These formulations are meant to be applied using a sprayer or water hose-end attachments.

Sprayers may be pressurized by air, using a hand pump or by water pressure during filling, as in the case of hose-end sprayers. Avoid spray drift to desired plants by using low pressure (to maximize droplet size) and by not applying when the wind is greater than 5 mph. Hose-end attachments force the herbicide into the water flow. The accuracy of herbicide application is low with this equipment. A more appropriate use of hose-end attachments is the application of fungicides, insecticides and liquid fertilizers.

Many postemergence herbicides are packaged as liquids ready to use for spot treatments in squirt bottles or aerosol cans. Be cautious with aerosol cans. They can be misdirected and the herbicide may contact your face and eyes. For spot treatments, many postemergence herbicide labels may provide directions for use with a brush and can. The liquid herbicide mixture can be "painted" with a brush (or cloth or sponge) onto undesirable plants. This method is convenient for treating individual plants or a few plants in small problem areas.

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