The role of host plant phenology in the development of the oak leafroller moth, Tortrix viridana L. (Lepidoptera: Tortricidae)

Abstract

Phenological coincidence between the insect and its host plant was studied in natural environment. Two phenological events were controlled: degree to which larval eclosion coincided with budburst in oaks, and synchrony between the duration of the insect development and growth of host plant leaves. Both factors varied from one season to another, and among the early, normal and late-flushing trees. These two phenological factors were compared in respect to their effect on the herbivore, using average pupal weights and densities as estimations of the insect success. Developmental synchrony to host plant appeared to be of a decisive importance for the successful development of the insect larvae. In contrast, the synchrony between eclosion and budburst did not influence strongly pupal weights and densities in given case, when variation in bud-flushing dates (about 10 days) did not exceed the T. viridana ability to resist starvation under the spring conditions. Two distinct peaks of larval eclosion from the eggs, collected in winter, were registrated under constant laboratory conditions. The larvae tended to hatch earlier on the trees with higher rates of average leaf growth (2-year data). Thus, two sympatric populations of the herbivore, differing in the dates of egg hatching, coexist in the same area.