Effects of quaking aspen density on the abundance and success of Lithocolletis salicifoliella in northern lower Michigan.

Abstract

Stand density has either a negative or positive effect on the success of an herbivore. This study examines the effect of density of aspen on the abundance and the fate of blotch miner Lithocolletis salicifoliella. Blotch miner larvae are herbivorous and feed on the cortex of quaking aspen leaves. The abundance and fate of miners were observed on two 20x20 m plots of different aspen densities, high density (HD) and low density (LD). Abundance of miners was determined by counting the number of leaf miners on each leaf for 50 trees at each site. We also determined the fate of the miners on leaves picked haphazardly from HD (n=80) and LD (n=80). The miners were categorized as alive or dead and if dead then victims of predation, parasitism, or other causes of death ""other"". Significantly higher numbers of miners per leaf were found at the HD stand. There was no significant difference in survival frequency between the HD and LD sites. There was a difference in the type of death incurred by the miners at low vs. high density stands. Predation was higher than expected in the LD and parasitism was higher than expected in the HD stand. The higher abundance of the miners in the HD stand can be attributed to availability of food plant and lack of increased predation and parasitism. Therefore the miners in the HD stand are more successful.