A new logarithmic sprayer for dose-response studies in the field

Abstract

Logarithmic sprayers are commonly used for dose-response studies in Plant Protection for a wide range of pesticides. Until now, logarithmic sprayers work on the principle of steadily diluting a predefined pesticide mixture with water. The objective of this study was to develop and test a logarithmic sprayer with a stepwise dose decrease. A predefined volume of an initial dose was sprayed. Part of this mixture was transferred in a second spray bottle and refilled with water. Afterward, a second dose of the same volume was applied, yet, with a predefined dilution ratio. This procedure was repeated for every dose level. With a 50% dose reduction (logarithmic spraying) a prototype of this logarithmic spraying technology was calibrated with laboratory measurements and tested in a field trial, applying glyphosate as a nonselective herbicide. The doses in the sprayer were almost equal to the manual dilutions (R2 = 0.9993), and the field experiment resulted in plots where the sprayed medium was uniformly distributed inside the plot, with a relative standard deviation of around 0.06, and in all cases less than 0.13. This facilitates measuring the herbicide efficacy for each dose. The new logarithmic spraying technology can significantly improve the accuracy and applicability of dose-response studies in field trials.