We report the uptake
of a lipophilic fungicide into the cuticle
of living leaves of young maize from droplets of a suspension concentrate.
The action of a “coffee-ring” effect is demonstrated
during fungicide formulation drying, and the fungicide particle distribution
is quantified. We develop a simple, two-dimensional model of uptake
leading to a “reservoir” of cuticular fungicide. This
model allows inferences of physicochemical properties for fungicides
inside the cuticular medium. The diffusion coefficient closely agrees
with literature penetration experiments (Dcut≈ 10–18m2s–1). The logarithm of the inferred cuticle–water partition coefficient
log10Kcw= 6.03 ±
0.04 is consistent with ethyl acetate as a model solvent for the maize
cuticle. Two limiting kinetic uptake regimes are inferred from the
model for short and long times, with the transition resulting from
longitudinal saturation of the cuticle beneath the droplet. We discuss
the strengths, limitations, and generalizability of our model within
the “cuticle reservoir” approximation.