A TEST OF PLANT-VIGOR, PLANT-STRESS, AND PLANT-GENOTYPE EFFECTS ON LEAF-MINER OVIPOSITION AND PERFORMANCE

Phyllonorycter sp. (Lepidoptera: Gracillariidae) preferentially ovipos ited on leaves of vigorous potted and wild Salix lasiolepis Benth. (Sa licaceae) host plants. A given unit of leaf area on a vigorous potted host plant was also more likely to be oviposited on, but this was not true of vigorous wild plants. These patterns of host use increased Phy llonorycter survival by reducing mortality associated with premature a bscission of Salix leaves and shoots. An in situ common garden experim ent demonstrated that Phyllonorycter densities and performance were no t influenced by the clonal identity of potted host plants. Drought tre atment of potted plants reduced shoot lengths and xylem water potentia l, but did not influence Phyllonorycter density.