• Double-check your sprayer for mechanical problems before you start using it.  You won’t have time to do this when planting is in full swing. 

• Clean the sprayer tank thoroughly and make sure nozzle filters are clean. 

• Clean spray nozzles, check their flow rates, and replace the ones that are spraying more than 10 percent of the original output. 

• Check the agitator in the tank to make sure it’s working properly. 

• Run water through the spray system to make sure everything is working properly 

• Find out if the sprayer is delivering the proper application rate (gallons per acre).  

One can determine if the chemicals are applied at the proper rate only by carefully calibrating the sprayer. Calibration, perhaps more than anything else, will have a direct impact on achieving effective pest control and the cost of crop production. While applying too little pesticide may result in ineffective pest control, too much pesticide wastes money, may damage the crop and increases the potential risk of contaminating ground water and environment.

Results of "Sprayer Calibration Clinics" I participated in Ohio, and data from several other States show that only one out of three to four applicators are applying chemicals at a rate that is within 5 % (plus or minus) of their intended rate (an accuracy level recommended by USDA and EPA). Of those two-thirds of the applicators missing the mark, about half is under spraying while the other half is over spraying. In one particular case, the applicator would be over spraying by as much as 75% had he used the nozzles that he just purchased and installed on the boom.  

Sprayers should be calibrated several times a year. Changes in operating conditions and the type of chemical used require a new calibration. Frequent calibration is even more important with liquid application because nozzles wear out with use, increasing the flow rate. Over a decade ago, my colleagues at University of Nebraska conducted an interesting survey.

The survey results revealed that there is a direct positive correlation between application accuracy and the frequency of calibration. Approximately 67 percent of the operators who calibrated before every spray operation had application errors below 5 percent. Only 5 percent of the applicators who calibrated their equipment less than once a year (once every two, three, four years) achieved the same degree of application accuracy.            

There are several ways to calibrate a sprayer. Regardless of which method you choose, it usually doesn’t take more than 30 minutes to calibrate a sprayer, and only three things are needed: a watch or something to count seconds, a measuring tape, and a jar graduated in ounces.

I will go over an easy way to calibrate a sprayer in the next issue of the newsletter. In the mean time, you can check the OSU Extension publication on boom sprayer calibration. Here is the URL for this publication: http://ohioline.osu.edu/aex-fact/0520.html