First Report of Stigmina lautii in the United States.

Abstract

In June 1999, a specimen of blue spruce (Picea pungens) from Avery County, North Carolina, exhibiting symptoms of needle blight was submitted to the Plant Disease and Insect Clinic at North Carolina State University. A fungus sporulating profusely on symptomatic needles was identified as Stigmina lautii. Since then, three additional specimens have been received-on blue spruce from Ashe County, on Norway spruce (P. abies) from Avery County, and on Picea sp. from Cherokee County. These counties are all in western North Carolina but are not contiguous, indicating that the fungus is probably widespread in the western part of the state. S. lautii was described by Sutton (2) in 1973 on black spruce (P. mariana) and white spruce (P. glauca) collected from various locations in Manitoba and Saskatchewan, Canada. The only other reference found to the fungus is a specimen collected in British Columbia, Canada, on P. glauca in 1972 (2). The morphology of the North Carolina specimens of S. lautii is essentially as described by Sutton. The dark brown, superficial, flattened sporodochia are developed only through stomata. Sporodochia are found both on symptomatic needles as well as on adjacent green needles. Conidiophores arise only laterally from the lower, outer cells of the sporodochium, and are macronematous, mononematous, brown, smooth, unbranched, 1 to 2 septate, and 10 to 20 × 4 to 6 μm. Conidiogenous cells are brown, monoblastic, integrated, terminal, percurrent with 3 to 4 annelations, and 6 to 12 × 4 to 5 μm. Conidia are pale brown, cylindrical to fusiform, often curved, thick walled, verrucose, 5 to 8 distoseptate, and 25 to 45 × 5 to 6 μm. Superficially, the sporodochia of S. lautii might be confused with pycnidia of Rhizosphaera kalkhoffii, which also arise through stomata. The latter fungus also is associated with a needle blight of Picea spp. in western North Carolina. Both fungi were present on one specimen examined. Currently, no information is available on the pathogenicity of S. lautii, but its association with typical needle blight symptoms and the known pathogenicity of other Stigmina spp. on conifers make it likely that the fungus is pathogenic to spruce. To my knowledge, this is the first report of S. lautii in the United States, and P. pungens and P. abies represent new host records for the fungus. Specimens BPI 747910 and 840959, have been deposited in the herbarium of the National Fungus Collections, Beltsville, MD.