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ARS Home » Research » Publications at this Location » Publication #107334


item Farr, David
item Castlebury, Lisa

Submitted to: Mycologia
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/28/2000
Publication Date: N/A
Citation: N/A

Interpretive Summary: Ragweed is a noxious plant that destroys thousands of acres of arable land as well as causing an allergic reaction in many people. Biological control agents are needed to reduce the spread of ragweed. A fungus belonging to the asexual genus Septoria has been discovered in Europe but its identity has remained obscure. Following a search of the literature, it was determined that this fungus was a previously undescribed species. For this project this fungus new to science is named, described and illustrated. Scientists will use this work to communicate about this fungus in developing it as a biocontrol agent for ragweed.

Technical Abstract: Bohr & Schwarczinger (Plant Dis. 83:696, 1999) reported that a species Septoria was pathogenic on Ambrosia artemisiifolia causing leaves to become completely necrotic and the death of some plants. Since this fungus might have some biocontrol potential a clarification of its taxonomy was required. Morphological investigations of the Septoria of Bohr & Schwarczinger showed that it is distinct from other related species and is described as a new taxon, Septoria epambrosia. Three species of Septoria have previously been reported on Ambrosia; S. ambrosiae, S. baciligera and S. ambrosiicola. The conidial dimensions of S. epambrosia are significantly different in both length and width from the other species of Septoria on Ambrosia. The numerous thickenings on the walls of the conidiogenous cells are another distinguishing characteristic. Black slow-growing colonies are formed in potato dextrose agar. The pycnidia formed in culture are different from those formed on Ambosia in that they are black and rostrate. Similarly shaped pycnidia are formed on inoculated alfalfa stems placed on water agar.