Impact of the equilibrium relationship between deposition and wettability behavior on the high-efficiency utilization of pesticides.

Abstract

Often, due to the occurrence of powdery mildew, cucumber leaf surfaces is changed into a more hydrophobic surface, which affects wetting and spreading of liquid pesticides, reducing their efficiency. The wetting and deposition behavior of liquid pesticides can be improved by adding surfactants to pesticides. Added surfactants affect the spray volume of the pesticide, which can lead to waste and a low utilization rate of the pesticide. It is important to further balance the relationship between deposition and wettability of pesticide liquid on the surfaces of healthy leaves and powdery mildew leaves of cucumber. This study evaluated the deposition and wettability of hexaconazole (Hexa) with surfactants on the surfaces of healthy leaves and powdery mildew leaves of cucumber. The deposition rates of Hexa with surfactants were lower than that of Hexa due to the loss of solution in conventional spray volume (750 L ha-1 ). The deposition rate of Hexa did not necessarily increase with increasing spray volume, and the deposition rate did not increase again after the spray volume increased to a certain level. Under the condition that the prevention and control effect were not reduced, we found that the volume of solution spray with added Silwet618 or AEO-5 should be adjusted to half of the normal volume, while the volume of solution spray with added 1227 or rosin-based quarternary ammonium should be adjusted to two-thirds of the normal volume to increase the deposition rate by approximately 30%. Regarding the wetting parameters, the results showed that the wettability of Hexa with Silwet618 was the best, but their combination was not ideal according to the composite index and deposition. By analyzing all the parameters, it was found that the spray volume reduction of Hexa with surfactant was approximately equal to the solution surface tension reduction, compared with the parameters of Hexa. The equilibrium relationship between deposition rate and wetting parameters was determined to provide guidance for the application of surfactants and to lower the dosage of pesticides to increase their efficiency and reduce their application. © 2021 Society of Chemical Industry.