Abstract Invasive weeds can increase agricultural biosecurity risks by serving as reservoirs for emerging or undercharacterized plant pathogens. Garlic mustard (Alliaria petiolata), an invasive brassicaceous weed in North America, occurs near agricultural landscapes and is susceptible to multiple crop pathogens. A previously undescribed Alternaria species was isolated from a diseased garlic mustard population in Maryland, USA, prompting investigation of its taxonomy, origins, and host range.
