Response of dwarf mistletoe-infested ponderosa pine to thinning. 1, Sapling growth

Abstract

Following overstorey removal in an overmature stand in Oregon, no difference in rate of growth was found when plots of healthy saplings thinned to 250 trees/acre were compared to similar plots parasitized by Arceuthobium campylopodum. Abundance of mistletoe on individual trees increased progressively during the first 10 yr of observation. After a second thinning and understorey vegetation control on infested plots, height growth was good and dwarf mistletoe remained largely limited to lower portions of tree crowns. Results indicate that parasitized saplings on average or better sites in the Pacific Northwest can be managed by wide spacing that increases tree height growth in spite of abundant dwarf mistletoe. As long as rapid increase in height continues, this treatment will produce trees with healthy upper crowns and an acceptable rate of growth. Managing infested stands to complete the rotation may be a preferable alternative to clear felling and replanting.