Calculating the area of a **CIRCLE**

Knowledge of the area of a circle may be needed when applying pesticide products to an area. At some point you may need to know how to calculate the area of a field which may have a circular shape. The information below may be of some help when calculating the field area.

Pi = is also an irrational number or the number 3.14159

Pi never changes and is used in this equation to determine the area of a circle.

Pi *x* r^{2} = the area of a circle

The diameter of a circle is measured from one edge of the circle to the opposite edge.

r = is the radius

The radius is half of the diameter, or a measurement from the center of a circle to one edge.

What is r^{2}? It is the radius multiplied by itself.

If the diameter was 20 feet across from edge to edge, the radius would be 10 feet. Therefore, to square the radius, you would multiply 10 x 10, which equals 100 feet.

If you have a circle that has a diameter of 20 feet, the radius would be 10 feet, therefore r^{2} would be 100 feet. So, you would multiply 3.14159 x 100 feet which equals the area of the circle. The total would be 314.159 square feet.

I hope you enjoy your Pi…………….

DH

**How to calculate the area of a RECTANGLE or SQUARE**

Area = Base *X* Height

**How to calculate the area of a TRIANGLE**

Area = Half of the Base *X* Height

**How to calculate the area of a TRAPEZOID**

Add the length of the top and bottom lines together and divide by 2

Multiple the average from above by the distance or height between the two lines

**WORKING WITH PERCENTAGES**

Many pesticide products are applied as spot treatments which are mixed with water at a specific “percent solution.” To create a pesticide solution, convert the percentage of concentrate in the final solution to a decimal before calculating the amount of concentrate to mix with water. To convert percentages to decimals, divide the percentage number by 100 to bet the decimal. This is equivalent to moving the decimal point two places to the left and adding zeros as needed.

Example: Mix 3 gallons of a 2% pesticide solution in water.

- Convert 2% to its decimal equivalent: 2 / 100 = 0.02
- To determine the number of fluid ounces of a pesticide needed per gallon: Multiply the rate per gallon (0.02) by 128 (ounces in 1 gallon) = 2.56 fluid ounces
- To determine the amount of pesticide needed: Multiply the amount of pesticide per gallon by the total spray mixture: 2.56 fluid ounces / gallon x 3 gallons = 7.68 ounces.
- Mix a little less than 8 ounces of pesticide with slightly less than 3 gallons of water to make a 2% solution. ADJUVANTS are typically added to pesticide mixtures on the basis of the final solution. When using adjuvants, use the type in which the manufacturer recommends, because using the incorrect adjuvant may cause issues.

**MEASUREMENT CONVERSIONS****Liquid **

1 Cup = 8 fl. ounces or 16 tablespoons

1 Gallon = 128 fl. ounces or 8 pints or 4 quarts

1 gallon of water weighs 8.345 pounds

1 fluid ounce = 0.0625 pints or 0.0313 quarts

1 fluid ounce = 0.0296 liters or 6 teaspoons

1 tablespoon = 3 teaspoons or 0.5 ounces (liquid)

1 teaspoon = 0.17 ounces (liquid) = 4.93 milliliters

1cc = 1 milliliter

1 fl. ounce = 29.57 milliliters

1% per gallon = 1.28 fluid ounces

1 inch of rainfall/acre = 27,154 gallons

**Dry**

1 pound = 0.453592 kilograms

1 ounce (dry) = 0.03 kilograms or 0.0625 pounds

1 ounce (dry) = 28.3495 grams

**Area Measurements**

1 mile = 5,280 feet

1 hectare = 2.471 acres

1 acre = 43,560 sq.feet

1 meter = 3.28 feet

1 yard = 3 feet

**Hand/Backpack Sprayer Calibratio**n

1) Determine the amount of area that can be sprayed with a given volume using the following equation:

a) Acres = Volume of tank / Gallons Per Acre (GPA)

Example: 2.5 acres = 5 gallon tank / 2 GPA

2) Determine how much pesticide to add to a tank using this equation:

a) Labeled rate *x* acres = amount to add to the tank

Example: 8 ounces of pesticide per acre* x* 2.5 acres = 20 ounces added to the tank

**Application**

1) Measure out and 18.5 by 18.5 foot square in the target area.

2) While maintaining consistent pressure, spray the area uniformly with water and record the number of seconds require to cover the area

3) For the same amount of time, spray into a large bucket with the same consistent pressure.

4) Fluid ounces of water collected = Gallons per Acre (GPA).

**Mixing Information**

Read and follow the label directions for proper mixing.

Prior to mixing products that are not mentioned on the pesticide label, mix small amounts of each in water, using separate containers and slowly add one mixture into the container that holds the other mixture to test for compatibility. Do this prior to mixing large batches. If the two mixtures clabber, you see precipitate or they begin to heat, the mixture may not be chemically compatible. Spray the mixture on a small portion of the area you intend to treat and wait three days, if you notice plants dying, you will know the mixture is phytotoxic and both materials should not be mixed and applied to larger areas for treatment.

**Pesticide Storage**

Read the pesticide label. It provides information concerning the proper disposal of the pesticide.

Store pesticides in a dry, well lit, well-ventilated space.

Post warning signs and lock the storage facility when not in use.

Store liquid pesticides on the bottom shelf and not on the floor.

Separate herbicides from other pesticides and other materials.

Use separate sprayers for herbicides and other pesticides.

Do not allow products to freeze or reach over 110 degrees F.**Disposal Information**

Read and follow all label directions for disposal.

Triple rinse empty containers as directed by the label prior to disposal.

Dispose of tank rinsates on the application site.

**Cleaning**

Clean spray tank and hose after every use.

A neutralizing agent may be needed to remove any remaining pesticide residues.

Use a soft bristle toothbrush to clean the nozzles, do not use a pin, wire or paperclip.

Never use your mouth to clean out clogged nozzles.

**The Environment**

Remember, honeybees are active mid-day, so pesticide applications should be made in late evening and remember not to spray when plants are in bloom.

Follow the label when applying pesticides; do not apply pesticides within 100 feet of creeks, streams, ponds, rivers or lakes.

**OTHER CALIBRATION RESOURCES**

A Simple Method to Calibrate Sprayers W315.pdf (tennessee.edu)

The 1/128 Calibration Method for Backpack Sprayers – Alabama Cooperative Extension System (aces.edu)

Tennessee Department of Agriculture’s (TDA) Termiticide Calculation page