Montana State University

Pesticide applicators can save money by following three spring tips

April 23, 2014 -- MSU News Service

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BOZEMAN – Pesticide applicators can save money by inspecting their spray equipment, calibrating their sprayers and testing the quality of their water before spraying, said Montana State University Extension Pesticide Education Specialist Cecil Tharp.

“It’s easy for applicators to focus on purchasing pesticide products while neglecting to calibrate the output of their spray equipment or test the quality of their water being used for spray applications,” Tharp said.

Offering three tips for spring spraying, Tharp recommended first that applicators inspect their spray equipment by checking spray pumps, lines, hose clamps and fittings for leaks and assessing the entire sprayer for rust, wear and breakage. Applicators should also inspect nozzles to see if the screens are free of debris and each nozzle spray pattern is uniform.

“A finely tuned ground sprayer in the fall may deliver a vastly different spray output in the spring,” Tharp said. “Rusted nozzles, ruptured seals or rust in the lines may eventually lead to uneven spray patterns or a significant departure from desired target flow rates.

To check the spray pattern, Tharp suggested that applicators spray water over gravel or concrete. If the spray pattern seems uneven, they should replace or clean the nozzles. They should select a nozzle tip that’s rated for the width they want to spray.

In his second tip – calibrating sprayers – Tharp said the goal is to make sure that the output of their sprayer falls within the range required on many pesticide product labels. Once applicators determine the output of their sprayers, they can determine how much pesticide product to add to a tank. For more information on calibrating sprayers, Tharp suggested applicators go to and select “Reference materials” at the lower right side of the web page. He recommended applicators either download and print the MontGuide titled “Calibrating Ground Sprayers Using Shortcut Methods” or refer to the calibration PocketGuides.

In his third tip – checking water quality before mixing solutions – Tharp said many applicators don’t realize that water quality affects pesticide effectiveness. A pH over 8, for example, may lead to a 50 percent loss of 2.4-D amine efficacy within a few hours. In addition, glyphosate (Roundup, for example) formulations lose efficacy if hardness exceeds 150 parts per million.

“Water quality can significantly lower pesticide performance of many pesticide products,” Tharp said. “Vast areas of Montana harbor ground water with less than ideal pH and/or hardness for spraying common pesticides.”

Applicators can test their water with a pH meter or pH litmus strips, Tharp said. If pH is a problem, applicators should consider using alternative sources of water or adding a buffering agent to adjust the pH. For more information on water quality, a new MontGuide titled “Pesticide Performance and Water Quality” is available by going to and selecting “Reference materials.”

For more information, contact Tharp at (406) 994-5067 or

Evelyn Boswell, (406) 994-5135 or