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Understand Sprayer Calibration Before Applying Pesticides

pesticide sprayer calibration

I teach several pesticide education classes each year, and I spend a good bit of time during these classes on sprayer calibration. For this example I will be discussing handgun/wand sprayer calibration, but we have information on boom and boomless sprayer calibration as well. It is extremely important to understand sprayer calibration before applying pesticides.

For farmers and other professionals, the pesticide label will tell you how much of the pesticide to apply per acre. So how much pesticide do you put in a tank? First we need to determine how many gallons of water you are applying per acre, then we can calculate how much pesticide to add to the tank. In this example we will use the 1/128th acre method, but other methods could be used. This method discussed here is for the handgun or wand applicators and does not matter if your sprayer is a handheld sprayer, backpack sprayer, ATV sprayer, or a larger sprayer mounted on a tractor.

First, measure 128th of an acre, which is about 340 square feet or 18.5 feet by 18.5 feet. You can use flags, string, spray paint, etc. to mark the area. Then, with only water in the tank, measure the time required, in seconds, to spray the area. The goal is to apply the water consistently, so try it several times until you determine your average time. Wetting the area more or less will change the calibration rate. The goal is to spray the same way in the field as you did while calibrating.  Then, spray the water in a container and measure the ounces caught. The ounces caught in the time required to spray the 340 square foot area equals the gallons of water the applicator is applying per acre.

In our example, we will say it took 23 seconds to spray the 340 square feet area. Spray is collected for 23 seconds and measured in ounces. If 50 ounces were caught, the applicator would be applying 50 gallons of water per acre. If 15 ounces were caught, you would be applying 15 gallons per acre. If 25 ounces were caught, you would be applying 25 gallons of water per acre. To adjust the gallons of water per acre, you may change pressure at the pump, change or adjust spray tips, or adjust the speed.  Then repeat the calibration process until you are applying the desired amount per acre. Once you are applying the desired volume of water per acre, you do not need to adjust the pressure, tips, or speed.

Once you calculate the area that can be covered with one tank, you can determine the amount of pesticide needed per tank. The pesticide label will give a range of desired gallons of water per acre that is needed to be applied along with the recommended rate of pesticide. Remember to read and follow the label directions before applying pesticides.

On our web site, we have information on pesticides that are labeled for certain crops, such as insects, disease, and weed control in turf, ornamentals, vegetables, fruit, forages, and other areas such as insects in wood structures. If you need more information on sprayer calibration, just contact your local County Extension Office or visit our web site at www.aces.edu and type sprayer calibration in the “Search ” box.

I work several counties in this region of the state in the area of Commercial Horticulture. Commercial Horticulture refers to producing horticulture products and marketing them for a profit as part of a business. Crops that growers commonly produce are nursery crops, turf, fruits, vegetables, Christmas trees, and cut flowers. Commercial horticulture can also involve horticulture services such as landscaping or landscape maintenance.

Other Extension agents work in the areas of home horticulture, forestry and wildlife, money management, animal science and forages, 4-H, agronomic crops, human nutrition, family and child development, community development, and food safety and quality. I grew up working in agriculture, and I was using the Extension System long before I became an Extension employee. I know firsthand how important Extension agents can be, and I encourage anyone to participate in Extension programs when possible and contact Extension agents when needed.

by Dr. Chip East, Regional Extension Agent for Commercial Horticulture