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Fungicidal Control of Shoot Blight Caused by Sphaeropsis sapinea on Red Pine Nursery Seedlings. M. A. Palmer, Research Plant Pathologists, North Central Forest Experiment Station, USDA Forest Service, St. Paul, MN 55108. T. H. Nicholls, Research Plant Pathologists, North Central Forest Experiment Station, and C. F. Croghan, Plant Pathologist, Northeastern Area, State and Private Forestry, USDA Forest Service, St. Paul, MN 55108. Plant Dis. 70:194-196. Accepted for publication 13 August 1985. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1986. DOI: 10.1094/PD-70-194.

Benomyl, thiophanate-methyl, and fentin hydroxide were evaluated for control of shoot blight caused by Sphaeropsis sapinea on second- and third-year Pinus resinosa seedlings. Only benomyl was effective. Benomyl applied twice 14 days apart during August allowed 4% disease incidence in treated first-year seedlings versus 34% in untreated controls in the most severe of three annual tests. Somewhat better control was achieved with five or seven applications from July through August or from June through August, respectively. Severe infection occurred during the second year of growth if seedlings were not protected during the first year. Four benomyl applications at 14-day intervals during budbreak and shoot elongation (late April through early June) allowed only 4% incidence of second-year infection versus 33% in untreated controls. Where benomyl was applied during the first but not the second year of growth, incidence of shoot blight during the second year was 5.2%. Least infection (2.7%) occurred when benomyl was applied for two consecutive years.

Keyword(s): Diplodia pinea.