Long-term impact of a leaf miner outbreak on the performance of quaking aspen

The aspen leaf miner, Phyllocnistis populiella Cham., has caused widespread and severe damage to aspen in the boreal forests of western North America for over a decade. We suppressed P. populiella on individual small aspen ramets using insecticide at two sites near Fairbanks, Alaska, annually for 7 years and compared plant performance with controls. Insecticide treatment successfully reduced leaf damage by P. populiella during most years and had little effect on herbivory by externally feeding invertebrates. By the end of the study, control ramets had suffered a reduction in height and girth relative to treated ramets and to the original, pretreatment size. Control ramets produced smaller leaves during some years and, after 7 years, produced fewer total shoots and leaves than ramets sprayed with insecticide. Treatment did not affect mortality, but at the warmer of the two sites, ramets sustaining ambient levels of leaf mining were significantly more likely to die back to basal sprouts than those treated with insecticide. We conclude that a decade of P. populiella outbreak has caused strongly negative effects on aspen development and the production of aboveground tissues.