Abundance and mortality of leaf miners on artificially shaded Emory oak

Abstract

ABSTRACT. We measured solar radiation reaching ten Quercus emoryi Torr. trees and recorded densities of four leaf‐mining insect species on these trees from June until September 1982. The measurements showed that densities of two leaf miner species were negatively correlated with solar radiation. In a field experiment, polypropylene shade fabric was suspended 1.3 m above four experimental trees to test for effects of reduced sunlight. Leaves of experimentally‐shaded trees were heavier and contained lower percentages of proteins and gallotannins than leaves of control, sun trees, while per cent foliar monomeric, polymeric, and total phenols, and water content did not differ between sun and shaded trees. Two of four leaf miner species had greater densities on experimentally‐shaded trees than sun trees. One of these two species experienced lower survivorship on sun trees owing to high levels of death from unknown causes on sun trees. Two leaf miner species had greater densities on sun trees. One of these species had higher survivorship on shaded trees owing to high levels of parasitism on sun trees. We conclude that even subtle differences in shading influences leaf miner density and mortality; however, the effects of shading vary from positive to negative among leaf miner species.