DIY project: Building an accurate small-area sprayer

By |  July 22, 2015 0 Comments

Golf course superintendents often are required to accurately and uniformly apply low rates of pesticides over small areas where larger boom sprayers, handgun sprayers or even small hand cans do not work well. Additionally, applications around bunkers, landscape beds, sidewalks, etc., always are difficult to make accurately and uniformly.

My favorite (and easiest to make and use) sprayer is made by attaching a hand-held two- or three-nozzle boom to a 3- or 4-gallon backpack sprayer (Figures 1-3). Two-nozzle (model 6012) and three-nozzle booms (model 601D) are available for as low as $130 from R&D sprayers (www.co2sprayers.com). We use compression fittings for air hoses and also include a pressure gauge on the sprayer to maintain consistent pressure as we are pumping. Depending on walking speed, nozzle number and size, pressure, etc., spray volumes are typically in the 0.25 to 1.0 gal/1,000 sq. ft. range.

At Lochland Country Club, Hastings, Neb., Superintendent Craig Ferguson and his staff converted a walk-behind rotary spreader into a 5-foot wide boom sprayer that is powered by a battery-operated pump (Figures 4-7). The 8-gallon plastic tank they used was from an old foam marker system, but any small tank that is suitable for pesticides would suffice. It also includes a bypass system to ensure constant agitation. All of the other components are at your closest farm supply store or on the Internet. This sprayer is a little more complex, but it will be perfect for accurate applications to larger areas.

Calibrating these sprayers is identical to calibrating any boom sprayer

  1. Measure the time it takes to walk a known distance of a calibration course at a comfortable walking speed. The calibration course should be the equivalent of 1,000 sq. ft., so length of the calibration course depends on the width of your spray boom. You can use a speedometer on the walk-behind sprayer to maintain a consistent walking speed. We often use a metronome (also available at R&D Sprayers) to set a walking speed with the handheld sprayer. The metronome helps with consistent timing between steps.
  2. Measure the area in sq. ft. covered in the calibration course (width of spray boom coverage multiplied by the length of your calibration course). Again, 1,000 sq. ft. is a convenient area for the calibration course.
  3. Measure the output from all of nozzles in ounces or milliliters for the same amount of time it took to walk the calibration course and covert to gallons (128 oz./gal. or 3785 mls./gal).
  4. Assuming a 1,000 sq. ft. calibration course, your output is the answer to step No. 3 above in gals./1,000 sq. ft. or mls./1,000 sq. ft.

Example

  1. It takes 50 seconds to comfortably walk a 200-foot-long calibration course.
  2. The example sprayer is a three-nozzle, 5-foot wide sprayer, so 5 feet X 200 feet = 1,000 sq. ft. calibration course.
  3. Catching the output from each nozzle for 50 seconds, you find that total output is 130 oz. = 1.02 gal (128 oz./gal).
  4. The calibration for this sprayer = 1.02 gal/1,000 sq. ft

Ready access to a small area sprayer will make your operation more efficient and will prevent misapplications of pesticides to small areas that are difficult to spray with large spray equipment.

Photos: Zac Reicher, Ph.D.



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