Pesticide Use

Reduced-Risk Pesticides

EPA’s Conventional Reduced Risk Pesticide Program registers certain pesticides as “reduced risk.” These are pesticides that pose less risk to human health and the environment than existing conventional alternatives. Biological and antimicrobial pesticides are handled through separate registration processes.

Products given the Reduced Risk decision have been compared with existing alternatives currently registered on that use site. These are products that have:

  • low impact on human health
  • lower toxicity to non-target organisms (birds, fish, plants)
  • low potential for groundwater contamination
  • low use rates
  • low pest resistance potential
  • compatibility with Integrated Pest Management (IPM) practices

NOTE: Reduced risk pesticides included in the spray tables in this guide are under the “Reduced risk/Organic” headings within each pest.

Use of Adjuvants

Spray adjuvants are materials added to pesticides in order to enhance their effectiveness. Many insecticides and some fungicides are formulated by the manufacturers with their own adjuvants. Because of the breadth of conditions growers encounter in Utah and Colorado, additional adjuvants may further enhance the effectiveness of the product. However, select with care, considering all the factors that may affect spray performance. Use of the wrong adjuvant for the conditions can decrease product effectiveness. Many pesticides will state the type of adjuvant that can be used.

There are many types of adjuvants, including surfactants (ionic or nonionic wetting agents/spreaders that improve wetting of foliage), stickers, and emulsifiers, and agents that buffer, defoam, control drift, penetrate soil, filter UV, and more. Each type of adjuvant differs in the way it interacts with spray chemicals and water quality, and weather conditions further affect their potential use. Thus, no one adjuvant can or should be used under all conditions.

Remember that amount and type of the adjuvant needed will vary with the hardness and pH of the water. Use just enough spreader-sticker to break the surface tension and spread the spray uniformly over the leafy surfaces; excessive amounts of surfactants will increase spray runoff. Do not use spreader-stickers with growth regulators (unless specifically called for on the label).

Adjusting for Water pH

The pH of water used to prepare spray solutions is very important. Water in many locations in Utah and Colorado is alkaline, ranging in pH from 7.4 to 8.5. The use of alkaline water for spray solution preparation can rapidly decompose many insecticides and decrease their activity. The following procedure is strongly recommended:

  1. Check the pH of your water supply.
  2. Read labels to determine whether water pH is important for that material.
  3. If necessary, adjust water pH before adding any chemical or pesticide that is sensitive to pH. pH adjusters include Buffercide, Buffer-X, Unifilm-B, and LI 700 Acidiphactant.
  4. Apply spray solutions as soon as possible after mixing in the spray tank. Especially avoid leaving mixed spray solutions in the spray tank overnight.

Conversion factors for weight or volume

Wettable powders (W) and dry flowable (DF) formulations*
1 lb = 453.6 grams
1 oz = 28.4 grams
¼ teaspoon (tsp) = 1.25 ml
½ tsp = 2.5 ml
 ¾ tsp = 3.75 ml
 1 tsp = 5 ml
 1 ½ tsp = 7.5 ml
 1 tablespoon (tbs) = 15 ml
 1 gal = 4 qt = 8 pt = 16 c = 128 fl oz = 256 tbs = 768 tsp
1 fl. oz. = 2 tbs = 6 tsp = 30 ml
*Dry materials differ in density and render the use of volumetric conversions (to tablespoon/teaspoon equivalents) approximate.  Weighing the material provides a more exact conversion. 

Sprayer Calibration

Calibration is important so that the amount of spray you think you are applying for a known area is accurate. A sprayer may be used one way to spray insecticides, and another way to spray herbicides. Calibration should be done with a sprayer that will be used for a particular application, in the same manner that the pesticide will be applied. How to calibrate and calculate how much material to use:

  1. Put a known volume (V) of water in the sprayer. Spray the water out in the same manner the pesticide will be applied, then determine the area in square feet (A), that was sprayed.
  2. To calculate the area in acres that are sprayed by V, divide A by 43,560. For example, if V=1 gallon, and the spray covered 1,075 sq. ft., then the area treated by 1 gallon is 1,075÷43,560 or 0.025 acre.
  3. Next, mix only enough spray to cover the area. If you need to spray 2,000 square feet and it takes 1 gallon to cover 1,075 square feet, dividing 2,000 by 1,075 gives you the number of gallons of spray that should be in the tank. In this case, 1.86 gallons are needed to cover the 2,000 square foot area.
  4. To calculate the amount of pesticide required for each gallon of spray, multiply the rate per acre on the pesticide label by the area you determined in step two above. In this example the area was 0.025 acre. If the rate per acre is 6 oz, the amount of pesticide for each gallon is 0.025 × 6, or 0.15 oz/gallon. Use the conversion factors in Table 12.2 to convert the amount into a unit that you can measure with your equipment.

Preparation of Small Spray Quantities

Label directions for mixing and applying pesticides come in two general scenarios: rate per volume (usually 100 gallons of water) or rate per area, (usually acre or 1000 sq. ft.) Mixing directions for small quantities of pesticide vary with the scenario.

If your pesticide mixing directions state an amount of material per 100 gallons, you should adjust the amount of pesticide to the volume of water you mix. Table 12.3 gives mixing rates for label instructions. If your label instructions state a final spray concentration, you do not have to calibrate the sprayer, but you must read the label to know how much spray material to apply.

If the pesticide mixing instructions state an application rate in an amount per area (usually acre, but sometimes 1000 sq. ft.), your sprayer must be calibrated.

Densities of solid pesticides vary with the formulation and the amount of shaking or settling within the package during shipping and in storage. An electronic scale should be used to ensure the correct weight of the dry product is used. These scales are readily available on-line and reasonably priced. Many of these scales measure down to 0.1 gram. The use of an electronic scale is essential for the solid form pesticides (e.g., wettable powders, dry flowables, etc.).

Do not use an ordinary teaspoon for measuring liquids as the common teaspoon varies from 4 to 10 ml. Instead, use a graduated medicine spoon. When measuring out small amounts you will need to use a syringe, which are available from your physician, veterinary supply, farm supply, or pharmacy. Graduated spoons and syringes used for a pesticide must not be used for anything other than that pesticide.

Conversion values for preparation of 1, 3, and 5 gallons of spray from the rate per 100 gallons.*

Materials Rate per 100 gal: 5 gal 3 gal 1 gal
& Dry Flowables
   4 lb 3.2 oz 2.0 oz 0.6 oz
   2 lb 1.7 oz 1.0 oz 0.3 oz
   1 lb  0.8 oz 0.5 oz  0.2 oz
   8 oz 0.4 oz 0.2 oz 0.1 oz
   4 oz 0.2 oz 0.1 oz 0.04 oz
   2 oz 0.06 oz 0.05 oz 0.02 oz
Liquid or
Concentrates, & Liquid
   1 gal 192 ml, or 12 tbs+2 tsp+2.0 ml 115 ml, or 7 tbs+2 tsp 38.4 ml, or 2 tbs+1 tsp+0.9 ml   
   2 qt 96 ml, or 6 tbs+1 tsp+1.4 ml 57.5 ml, or 3 Tbs + 2 ½ tsp 19.2 ml, or 1 tbs+¾ tsp+0.45 ml
   1 qt 48 ml, or 3 tbs+½ tsp+0.5 ml 28.8 ml, or 1 tbs+2 ¾ tsp+0.5 ml 9.6 ml, or ¾ tsp+1.05 ml
   1 pint 24 ml, or 1 tbs+1 ¾ tsp+0.25 ml 14.4 ml, or 2 ¾ tsp+0.65 ml 4.8 ml, or ¾ tsp+1.05 ml
   1 cup (8 fl oz=16 tbs) 12 ml, or 2 ½ tsp 7.2 ml 2.4 ml
   4 fluid oz or 8 tbs 6 ml, or 1 tsp+1.0 ml 3.6 ml 1.2 ml
   2 fluid oz or 4 tbs 3 ml, or ½ tsp+0.5 ml 1.8 ml 0.6 ml
   1 fluid ounce or 2 tbs 1.5 ml 0.9 ml 0.3 ml
The measurements in tablespoons and teaspoons are approximate. The use of an electronic scale and syringe will be much more accurate.