Parthenium hysterophorus (parthenium weed).

Parthenium hysterophorus is an annual herb that aggressively colonizes disturbed sites. It is considered as one of the '100 most invasive species in the world' by the IUCN (GISD, 2018). Native to the New World, it has been accidentally introduced into several countries and has become a serious agricultural and rangeland weed in parts of Australia, Asia, Africa and the Pacific Islands. It is reported as a major weed in field crops in more than 45 countries (Bajwa et al., 2016; Shabbir et al., 2019), with yield losses estimated in millions of dollars in Australia (Kaur et al., 2014). It grows on any type of soil and in a wide range of habitats. It affects the production of crops, animals, human and animal health, and biodiversity. Several characteristics, such as wide adaptability, photo- and thermo-insensitivity, lack of natural enemies in non-native regions, drought tolerance, strong competition and allelopathy, high seed production ability, longevity of seeds in soil seed banks, and small and light seeds that are capable of long distance travel via wind, water, birds, vehicles, farm machinery and other animal traffic, contribute to its rapid introduction world-wide, cutting across national boundaries and climate barriers (Kaur et al., 2014; Bajwa et al., 2016). The genetic diversity found among different populations and biotypes are also strongly contributing to its invasion success (Bajwa et al., 2018). The species is reported as invasive in various countries in Asia, Africa, and Oceania (Gnanavel, 2013; EPPO, 2018; GISD, 2018; PIER, 2018). In the Americas, it is reported as invasive in Cuba, and in Trinidad and Tobago. In Cuba it is considered as one of the most noxious species (Oviedo Prieto et al., 2012). Although listed as introduced by various sources it is also listed as native by others (USDA-ARS, 2018). In Trinidad and Tobago it is a predominant weed of industrial areas, crops, orchards, ornamentals and greenhouses (Bridgemohan et al., 2015).