Productivity, drought tolerance and pest status of hybrid Populus: tree improvement and silvicultural implications

Sixteen hybrid poplars, Populus spp., were evaluated during the first 3 years and in year 6 of plantation growth. Significant clonal differences were found in survival, growth, and susceptibility to pests. Drought tolerance varied among clones. Branch and secondary stem biomass, and biomass density were important factors in tree weight. Impacts of the fungal pathogen, Septoria musiva, and herbivory by the cottonwood leaf beetle, Chrysomela scripta, and the meadow mouse, Microtus pennsylvanicus, varied greatly among clones. Five clones, NM6, DTAC2, NC5377, NC11396 and NC11004, exhibited high rates of survival, productivity, and canker disease resistance. Clones NM6 and DTAC2 were highly and moderately resistant, respectively, to meadow mouse herbivory. Clone NC11396 was moderately resistant to the cottonwood leaf beetle. All other clones were susceptible to these pests. These results are discussed in regard to tree evaluation and improvement strategies, and multiple pest complexes.