“Manufacturers of spraying equipment easily recommend a speed of up to 20 km/h. However, the manufacturers of nozzles tell a different story,” writes Sakkie Koster, an agricultural consultant, in Grain SA’s magazine.
According to nozzle manufacturers, chemicals should be applied at maximum speeds of 6-8 km/h, or up to 10 km/h when using air induction tips. They also warn that speed must be reduced if the wind speed picks up.
“Nozzles are therefore developed to deliver a certain volume of water at a specific pressure and speed to deliver the required drops per square centimetre.”
Koster also points to other factors that influence fungicides’ effectiveness, including that they work better if they are used preventively, and that the effectiveness decreases significantly if they are not used with the correct volume of water.
“Research has shown that where the water volume is reduced, the number of drops per square centimetre decreases significantly – in fact to below the accepted norm.”
The wrong spraying equipment can also decrease the effectiveness of the drugs. “Research has shown that using stocking beam sprayers to penetrate the crop produces much better results than a regular sprayer. It was also suggested that the nozzle be set at an angle of 35 degrees to the front for better penetration. Where regular sprayers were used, the twin flat nozzles gave better results than the regular flat fan nozzles. Using the nozzle at the right pressure and speed is extremely important.”
Farmers are advised to follow the directions on the fungicide labels carefully in all cases.
