2019 Volume 101 Issue 6 Pages 322-327
We have investigated the effects of tree density and Diaporthe canker disease on the growth of sprouts of lacquer trees, Toxicodendron vernicifluum. We set up four density treatments: 1,600 trees/ha, 3,000 trees/ha, 6,000 trees/ha, and no treatment at a location where the trees had been clear-cut. We then investigated sprout height, stem basal diameter, and canker disease occurrence after two years. An analysis of variance indicated significant differences in stem basal diameter, with greatest diameters in the lowest density treatment. We found canker disease caused by Diaporthe toxicodendri and observed three main symptoms: blight, sprouting from a girdling canker, and sunken canker. The disease was found in 49.6％ of the 131 sprouts examined. We concluded that the stem basal diameters were widest in the 1,600 trees/ha treatment both because of the low tree density and because the ratio of sprouting from a girdling canker was low. These results indicate that stem basal diameter growth can be optimized by removing the diseased trees in areas affected by canker disease and maintaining trees at a density of 1,600 trees/ha.
