Pathogenicity of Rhynchosporium alismatis and its potential as a mycoherbicide on several weed species in the Alismataceae

Abstract

The inundative application of conidia of the plant pathogenic fungus, Rhynchosporium alismatis, to seedlings of Sagittaria pygmaea, S. guyanensis, and Alisma canaliculatum resulted in seedling death or significant growth suppression. In quarantine pot trials, inoculation of S. guyanensis seedlings caused reductions in average plant height of 60% and reduced leaf and root dry weights, by 89 and 84%, respectively. There was also high seedling mortality. Smaller, though significant, reductions in various growth parameters occurred in the other species when similarly inoculated. Alisma canaliculatum, Echinodorus rostratus, S. brevirostra, S. guyanensis, and S. pygmaea are recorded as new hosts of the fungus. The data indicate the potential use of this fungus as a mycoherbicide in temperate rice crops. Research is continuing on virulence and formulation to improve mycoherbicide efficacy.