Does Citrus leaf miner impair hydraulics and fitness of Citrus host plants?

Gas exchange and hydraulic features were measured in leaves of three different Citrus species infested by Phyllocnistis citrella Staiton, with the aim to quantify the impact of this pest on leaf hydraulics and, ultimately, on plant fitness. Infested leaves were characterized by the presence on the leaf blade of typical snake-shaped mines and, in some cases, of a crumpled leaf blade. Light microscopy showed that leaf crumpling was induced by damage to the cuticular layer. In all three Citrus species examined: a) the degree of infestation did not exceed 10% of the total surface area of infested plants; b) control and infested leaves showed similar values of minimum diurnal leaf water potential, leaf hydraulic conductance and functional vein density, and c) maximum diurnal values of stomatal conductance to water vapour, transpiration rate and photosynthetic rate (An) were similar in both control leaves and the green areas of infested leaves. A strong reduction of An was recorded only in mined leaf areas. Our data suggest that infestation with P. citrella doesn't cause conspicuous plant productivity reductions in young Citrus plants, at least not in the Citrus species studied here.