A report on the natural incidence of Puccinia noccae on the exotic weed Lagascea mollis in India

摘要

Lagascea mollis (=Nocca mollis (Cav.) Jacq. commonly known as Velvet weed or Silk leaf weed) is native of Tropical Central America and is an invasive annual herb belonging to the family Asteraceae. It is found to occur in most parts of the country, grows on cultivated land and in pastures along field bunds, roadsides and channels. It grows throughout the year but appears severe in the late Kharif (monsoon) and early Rabi (winter) seasons (July to November) natural infection by the rust pathogen, identified as Puccinia noccae was found to occur on the weed in and around the fields of Jabalpur district. The pathogen survives as dormant teliospores and on favorable climatic conditions produces the uredospores, which are the pathogenic stage of its lifecycle. The disease appears as scattered dull brown individual spots on the underside of the leaves, which later develops into rusty brown raised spots containing the urediniospores. The pathogen affects the green leaves and the bracts. General observations and host range studies indicated that P. noccae is highly specific on L. mollis and hence may be used as a biocontrol agent against L. mollis.