Trichome density and pesticide retention and half-life

In order to examine relationships between trichome density and pesticide retention and persistence, clones of 3 genotypes of Lycopersicon hirsutum Humb. & Bonpl. were grown in 3 photoperiod environments. Trichome density is a plastic character on this species, responsive to photoperiod. Leaves which differed in trichome density resulting from growth in the 3 photoperiods were then dipped in solutions of a short-lived insecticide, pirimiphos-methyl, and the quantity initially retained and persistence were determined. Initial retention of pirimiphos-methyl was highly correlated with type IV trichome density, the most numerous trichome on these leaves. Persistence was not related to trichome density, but differed among genotypes. Environmental manipulation of trichome density on L. hirsutum provides an experimental approach for examining the interaction of pesticides with trichomes, uncomplicated by differences among plant genotypes. Consequently this approach may allow a better understanding of pesticide interactions with plants.