Spread pathways of the invasive weed Parthenium hysterophorus: The potential for water dispersal

Segun Osunkoya and colleagues have published “Spread pathways of the invasive weed Parthenium hysterophorus: The potential for water dispersal” in Austral Ecology. Parthenium disperses by several methods; one possible mechanism being water. Several experiments were conducted to improve the understanding of water dispersal. They found that freshly harvested cypselae (single seeded fruit) could float on river water for at least 20 days though 80% sank within a week if moderate or severe turbulence was applied. Naked seeds sank more rapidly than cypselae. Germination occurred within a week on still water surfaces and 1.5 weeks under turbulent conditions. In river water, initial germination of floating cypselae was greater under illuminated than dark conditions. The rate of viability loss of immersed cypselae increased with water temperature. In summary, cypselae float in turbulent water and could be carried significant distances in river systems. Immersed cypselae remain viable for weeks and germinate on contact with soil. Water bodies or floods are therefore important pathways in parthenium weed dispersal and post-flood monitoring is strongly recommended to minimise its spread.

Mao, R., Nguyen, T.L.T., Osunkoya, O.O. and Adkins, S.W. 2019. Spread pathways of the invasive weed Parthenium hysterophorus L.: The potential for water dispersal. Austral Ecology 44(7): 1111-1122.