Effect of Lophodermium seditiosum on Growth of Pine Nursery Seedlings in Wisconsin. M. E. Ostry, Principal Plant Pathologists, USDA Forest Service, North Central Forest Experiment Station, St. Paul, MN 55108. T. H. Nicholls, Principal Plant Pathologists, USDA Forest Service, North Central Forest Experiment Station, St. Paul, MN 55108. Plant Dis. 73:798-800. Accepted for publication 5 May 1989. 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, 1989. DOI: 10.1094/PD-73-0798.

A needle cast disease caused by Lophodermium seditiosum has killed or severely damaged millions of red and Scotch pine seedlings in nurseries and Christmas tree plantations in many areas of the United States since the mid-1960s. Outbreaks of L. seditiosum periodically occur in nurseries when chemical control measures are not used or improperly applied. The impact of this disease on seedling height and diameter growth of three pine species grown in a Wisconsin nursery was studied. Pine seedlings were either protected with fungicides or left unprotected for 3 yr. In the nursery, seedling survival and height and diameter growth were significantly less in untreated than in treated plots. One year after outplanting, red pine seedling survival and height growth were not significantly different, but symptoms of Lophodermium needle cast were visible on 80% of the foliage of untreated seedlings and on only 20% of maneb-treated seedlings.