THE INFLUENCE OF SALIX LEAF ABSCISSION ON LEAF-MINER SURVIVAL AND LIFE-HISTORY

1. Early abscission of mined leaves was an important mortality factor of a Phyllonorycter species (Lepidoptera: Gracillariidae) on Salix lasiolepis Benth. (Salicaceae). A larger percentage of mined leaves abscised early (34.4% in 1990; 24.5% in 1991), and Phyllonorycter survival was greatly reduced in these abscised leaves. 2. Leaf-mining by Phyllonorycter was associated with increased early leaf abscission. An egg removal experiment demonstrated that leaf mining induced this increase in leaf abscission. 3. The induction of early leaf abscission was dependent upon the timing of herbivory and simulated herbivory (mechanical damage). Early mechanical damage induced leaf abscission, late mechanical damage did not. Mines which expanded early were more likely to induce leaf abscission than mines which expanded more slowly.