Temporal and spatial patterns of research on a globally significant invasive weed Parthenium hysterophorus L.: A bibliographic review

Parthenium hysterophorus L. is a globally significant environmental and agricultural weed that is rapidly spreading from its native range in the tropical Americas to tropical and subtropical regions of all continents. We analyzed temporal and spatial patterns of research done on this weed across the world. Research articles were accessed from online databases, Web of Science (WOS) and Chinese National Knowledge Infrastructure (CNKI) and previously published review articles. A total of 428 research articles in 161 SCIE/SSCI indexed journals was published from 1970 to December 2018 out of which 76% of the research was conducted in South Asia. Asian journals had more publications than European and American journals revealing concern for invasion, and more effort on the development of management strategies. Most of the research was conducted on potential uses (19%), allelopathic effect (17%) and phytochemical studies (13%) of this weed. Even though the plant has invaded 49 countries outside of its native range, research publications were available only from twelve (25%) countries. The extent of the geographic areas and ecosystems invaded by this weed is still not known for all the countries where it has been reported. We contend that the continuing spread of this weed is due to lack of timely and adequate knowledge and research in the introduced range. Our search of the literature indicates that to prevent the rapid spread of this weed and to economically manage this pest where it has already invaded, increased research activities and effective technologies for various control measures and competitive displacement by using different plants must be established in all the invaded countries.