THE EFFECTS OF HOST-PLANT PHENOLOGY ON THE DEMOGRAPHY AND POPULATION-DYNAMICS OF THE LEAF-MINING MOTH, CAMERARIA-HAMADRYADELLA (LEPIDOPTERA, GRACILLARIIDAE)

1. We examined the effects of variation in the timing of spring leaf production and autumn leaf fall on the survival, mortality and abundance of Cameraria hamadryadella on Quercus alba and Q.macrocarpa. 2. We monitored and manipulated the timing of foliation on field and potted Q.alba trees and observed the abundance of C.hamadryadella on those trees. We also monitored and manipulated the timing of leaf fall on Q.alba and Q.macrocarpa trees in the field and observed its effects on survival, mortality and abundance of C.hamadryadella. 3. Variation in the timing of spring leaf production has no effect on C.hamadryadella abundance. However, a warm winter and spring in 1991 led to accelerated development and the imposition of a facultative third generation in one out of ten years of observation. 4. In 1989, leaves fell relatively early and leaf fall in the autumn accounted for more than 50% of the mortality of C.hamadryadella. In 1990 and 1991 leaves fell relatively late and leaf fall induced mortality was substantially reduced and over-winter survival was markedly increased. 5. The abundance of C.hamadrvadella remained constant in the spring and summer of 1990 following the previous autumn's relatively early leaf fall, but increased by 10-fold in the spring of 1991 following the relatively late leaf fall of autumn 1990. The abundance of C.hamadrvadella also increased 4-fold between the summer of 1991 and the spring of 1992 after another autumn of relatively late leaf fall. We attribute these increases in abundance in part to reduced mortality because of later leaf fall. 6. Variation in the timing of autumn leaf fall may be responsible for initiating outbreaks of C.hamadryadella.