ABSTRACT
The effect of foliar wettability on the coverage and adhesion of various mixtures of systemic and protective fungicides based on mancozeb was evaluated. The product was applied using a “wet leaf” methodology, simulating spraying under conditions of high relative humidity or dew presence, where the pre-existing water film usually compromises adhesion to banana plant leaves (genus Musa). The results demonstrate that the 62% mancozeb suspension concentrate formulation achieved retention levels of 92%, greatly surpassing standard mixtures based on wettable powders or conventional emulsifiable concentrates. The data confirm that the product possesses superior mechanical fixation capacity due to the micrometric nature of the suspension, which optimizes adsorption capacity. This study also supports redefining field application methodologies for mancozeb suspensions, prioritizing dry application conditions, partial environmental humidity, and low precipitation.
INTRODUCTION
In commercial agrochemical applications, the condition of the foliar tissue is a determining factor in treatment efficacy. Persistence represents the resistance of the phytosanitary deposit to removal by external agents (rain, wind) from the foliar tissue, whereas adhesion is the molecular attraction between the product and the surface. This phenomenon reflects the interaction between the solid and liquid phases described in colloid chemistry; fungicide efficacy depends on its ability to establish an exchange complex or “adsorption” on the waxy cuticle. Fungicide stability on the leaf is determined by Van der Waals forces, interactions that determine material cohesion. At the cuticle-fungicide interface, these forces, together with hydrogen bonds, are responsible for agrochemical persistence. The formulation must act at the interface through electrostatic forces that stabilize the deposit against surface leaching. The research focused on determining how nighttime or morning humidity affects the retention of mancozeb-based fungicidal suspension concentrates when combined with different systemic agents and oils.
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