Controlling Diseases and Insects in Home Fruit Plantings

Bulletin 780-01

Measuring Small Amounts of Pesticide

The rate or amount of pesticide to use is listed on the product label. For most products packaged specifically for homeowner use, rates are given in teaspoons or tablespoons per gallon of water. With these products, homeowners have no problem measuring the exact amount of product they need to use. Many backyard growers choose to purchase larger quantities of pesticide that are packaged primarily for use by commercial growers. This is acceptable and in some cases, depending on the quantity of plants to be sprayed, may be more convenient and economical. In some situations, the preferred pesticide may not be available in homeowner packaging and commercial packages of 2 to 5 pounds are all that is available. A problem with commercial packages is that rates are often given in the amount of pesticide to use per 100 gallons of water. Commercial rates are also commonly given in the amount of pesticide to use per acre in a given amount of water. Problems arise when the homeowner reads the label that states, "Use 1 pound of pesticide per 100 gallons of water," and the homeowner needs only 1 gallon of pesticide mixture. For dry formulations of pesticide (powders), it is difficult to calculate the number of teaspoons or tablespoons required for 1 gallon of water when the rate is 1 pound per 100 gallons; approximations are given in Table 2. For liquid formulations, it is possible to calculate down to teaspoons and tablespoons.

Table 2. Approximate Dilutions for Small Volumes of Spray Mixes. Equivalent Rates for Different Quantities of Water Formulation 100 gallons 5 gallons 3 gallons 1 gallon Wettable Powder 5 pounds 15 tablespoons 9 tablespoons 3 tablespoons 4 pounds 13 tablespoons 8 tablespoons 8 teaspoons 3 pounds 10 tablespoons 6 tablespoons 2 tablespoons 2 pounds 8 tablespoons 4 tablespoons 4 teaspoons 1 pound 3 tablespoons 6 teaspoons 2 teaspoons 1/2 pound 5 teaspoons 1 tablespoon 1 teaspoon Emulsifiable Concentrate 5 gallons 1 quart 1 1/4 pints 13 tablespoons 4 gallons 1 1/2 pints 1 pint 10 tablespoons 3 gallons 1 1/4 pints 3/4 pint 1/4 pint 2 gallons 3/4 pint 1/2 pint 5 tablespoons 1 gallon 1/2 pint 8 tablespoons 3 tablespoons 1 quart 3 tablespoons 2 tablespoons 2 teaspoons 1 pint 5 teaspoons 1 tablespoon 1 teaspoon

The ideal method for weighing small amounts of pesticide is to use the metric system of measurement. Unfortunately, many of us are not equipped to use this system. The following information and the highlighted information on the left side of this page are provided to aid the homeowner in weighing small amounts of pesticide.

Dry Formulations Measurement Equivalents 1 pound = 16 ounces = 454 grams 1 ounce = 28.4 grams Sample Calculation for Determining Pesticide Concentration in English Units 1 pound of fungicide per 100 gallons of water equals 16 dry ounces of fungicide per 100 gallons of water equals 1.6 dry ounces of fungicide per 10 gallons of water equals 0.16 dry ounces of fungicide per 1 gallon of water Sample Calculation for Determining Pesticide Concentration in Metric Units 1 pound of fungicide per 100 gallons of water equals 454 grams of fungicide per 100 gallon of water equals 45.4 grams of fungicide per 10 gallons of water equals 4.5 grams of fungicide per 1 gallon of water

Liquid Formulations Measurement Equivalents 1 gallon = 4 quarts = 8 pints = 16 cups = 128 fluid ounces = 3785 milliliters 1 quart = 2 pints = 4 cups = 32 fluid ounces = 946 milliliters 1 fluid ounce = 2 tablespoons = 29.6 milliliters 1 tablespoon = 3 teaspoons = 14.8 ml = 1/2 fluid ounce Sample Calculation for Determining Pesticide Concentration in English Units 1 quart of pesticide per 100 gallons of water equals 32 fluid ounces per 100 gallons of water equals 3.2 fluid ounces per 10 gallons of water equals 0.32 fluid ounces per 1 gallon of water Sample Calculation for Determining Pesticide Concentration in Metric Units 1 quart of pesticide per 100 gallons of water equals 946 milliliters per 100 gallons of water equals 94.6 milliliters per 10 gallons of water equals 9.4 milliliters per 1 gallon of water