The Preparation of Small Spray Quantities
of Pesticides

Information provided by:
Dr. Harold Larsen
Tree Fruit Specialist
Western Colorado Research Center, Orchard Mesa

Labels on pesticides packaged for commercial application typically give the application rates in terms of either quantity per acre (most common) or quantity per 100 gallons of spray. Where the latter is used, the concentration of active ingredient (a.i.) within the spray mix is viewed as critical to the efficacy of the material. Where the former is used (quantity per acre), concentration of the a.i. is viewed as not being as critical as the total amount of a.i. applied per acre (defined as the land area beneath the treated plants). Early studies on spray application found that “spray to drip” typically applied approximately 400 gallons of spray per acre. This varied some with the adjuvants included within the spray mix; inclusion of a surfactant (spreader) accelerates the drip process and results in lower rates per acre (e.g., 350 gal./acre), while inclusion of a sticker slows the drip process and results in higher rates per acre (e.g., 450 gal./acre). Since use of a hand sprayer closely approximates a “spray-to-drip” application, the rates per acre have been converted to a rate per 100 gallons by dividing them by 4. This equates to an application rate by hand sprayer of 0.23 gallons (approximately 1 qt) per 10 ft x 10 ft (=100 sq. ft.) of treated crop area. These are the rates used in the table below.

Densities of solid formulation pesticides varies with the formulation and the amount of shaking or settling within the package during shipping (or in storage subsequently). Thus, proportional weights are the most precise for making small spray quantities. Electronic scales are now quite readily available and affordable. Many of these measure down to 0.1 gram. Their use is essential for the solid form pesticides (e.g., wettable powders, dry flowables, etc.). The following equivalents table (Table 1) assumes:

1. For wettable powders (W) and dry flowable (DF) formulations: 1 lb = 453.6 g & 1 oz = 28.4 g
2. For liquids: 1 gal = 4 qts = 8 pts = 16 cups = 128 fl.oz. = 256 Tbsp = 768 tsp
& 1 fl. oz. = 2 Tbsp = 6 tsp = 29.6 ml

 

Table 1. Conversion values for preparation of 1, 3, and 5 gallons of spray from the rate per 100 gallons.
Type of Material
Amount per:
  100 gallons 5 gallons 3 gallons 1 gallons
Wettable Powders, & Dry Flowables 4 pounds [lbs]
(1,814.3 grams)		 90.7 g 54.4 g 18.1 g
  2 lb (907.2 g) 45.4 g 27.2 g 9.1 g
  1 lb (453.6 g) 22.7 g 13.6 g 4.5 g
  8 oz. (226.8 g) 11.3 g 6.8 g 2.3 g
  4 oz. (113.4 g) 5.7 g 3.4 g 1.1 g
  2 oz. (66.7 g) 2.8 g 1.7 g 0.6 g
************************************************************************************************************************************
Liquids:
Liquid Concentrates, Emulsifiable Concentrates, & Liquid Flowables		 1 gallon (3,785 ml) 189 ml
(~80 teaspoons)		 114 ml
(~8 Tablespoons)		 37.9 ml
(~8 teaspoons)
2 quart (1,893 ml) 94.6 ml
(~40 teaspoons)		 56.8 ml
(~6 Tablespoons)		 18.9 ml
(~6 teaspoons)
1 quart (946 ml) 47.3 ml
(~20 teaspoons)		 28.4 ml
(~4 Tablespoons)		 9.4 ml
(~4 teaspoons)
1 pint (437 ml) 23.7 ml
(~10 teaspoons)		 14.2 ml
(~2 Tablespoon)		 4.7 ml
(~2 teaspoon)
  1 cup (8 fluid ounces = 237 ml) 11.8 ml
(~5 teaspoons)		 7.1 ml
(1 Tablespoon)		 2.4 ml
(~1 teaspoon)
  4 fluid ounces (118.3 ml) 5.9 ml
(~2.5 teaspoons)		 3.5 ml
(~.5 Tablespoon		 1.2 ml
(~.5 teaspoon)
  2 fluid ounces (59.2 ml) 2.96 ml
(~1.25 teaspoons)		 1.8 ml 0.6 ml
(~.25 teaspoon)
  1 fluid ounce (29.6 ml) 1.48 ml
(~0.63 teaspoon)		 0.9 ml 0.3 ml

Extracted from the Colorado Tree Fruits Pest and Crop Management Guide. Colorado State University Extension Publication Number XCM-41.

Placed on the Internet February 24, 1997

WebMaster Dr. Curtis E. Swift, Area Extension Agent, Horticulture
Colorado State Extension
2775 US Hwy 50, Grand Junction, CO. 81503
voice: 970-244-1834
fax: 970-244-1700