First Report of <i>Nigrospora oryzae</i> Causing Leaf Spots on <i>Ageratina adenophora</i> in India

ABSTRACT Ageratina adenophora , a globally invasive weed, poses a serious threat to native ecosystems. During field surveys in Uttarakhand, India, in 2023, a severe leaf spot disease was observed affecting large populations of A. adenophora . The causal fungus was identified as Nigrospora oryzae based on morphological characteristics combined with internal transcribed spacer (ITS) and β‐tubulin ( tub2 ) sequence analyses. Pathogenicity tests using conidial inoculations reproduced characteristic symptoms, and N. oryzae was successfully re‐isolated, thereby fulfilling Koch's postulates. As weeds can act as reservoirs of inoculum, understanding such pathogen–host associations is essential for assessing potential risks to economically important crops and for developing informed management strategies for invasive species. Further research on its host range, biosafety and potential as a biological control agent is also warranted to ensure safe and effective application. This study represents the first report of N. oryzae infecting A. adenophora in India and worldwide.