Influence of Sulfometuron Methyl on American Chestnut Seedling Growth and Leaf Function

The expected production, dissemination, and planting of blight-resistant hybrid chestnut seedlings calls for anticipatory studies to establish optimal management practices. To test phytotoxic potential of a site preparation herbicide, seedling growth and physiological function were measured for potted American chestnut (Castanea dentate [Marsh.] Borkh.). Six concentrations (0.0, 0.026, 0.053, 0.105, 0.158, and 0.210 kg active ingredient [ai] ha(-1)) of sulfometuron methyl (Oust) were applied to pots in April 2008, which were planted with 1 + 0 seedlings in May, and grown until November 2008. Changes in height, rootcollar diameter, and root volume and length were measured. A portable photosynthesis system was used to measure net photosynthesis, stomatal conductance, and transpiration. Seedlings treated with label-recommended doses (0.105-0.210 kg [ai] ha(-1)) showed growth and leaf function suppression, including 55, 71, and 82% reductions in height growth, root volume, and net photosynthesis, respectively. These results indicate that a strong need exists for field trials, with various dose regimes, to be conducted to refine an application rate that minimizes phytotoxic damage while still providing suitable control of competition vegetation.