Allelopathic potential of invasive parthenium weed (Parthenium hysterophorus L.) seedlings on grassland species in Australia

The allelopathic nature of adult Parthenium hysterophorus L. (parthenium weed) plants, suppressing the growth and development of its near neighbours, has been implicated in its success as an important invader around the world. This study for the first time, evaluates the allelopathic potential of parthenium weed seedlings, comparing its impacts upon seven introduced and four native Australian grassland species using the ‘plant box’ method (10). Results showed a species-specific response, often with the growth of native species being more affected than introduced species and root growth more affected than shoot growth. The native grasses [curly windmill grass (Enteropogon acicularis L.; 59% inhibition) and cotton panic grass (Digitaria brownii L.; 54% inhibition)] were the most affected, while the introduced [Rhodes grass (Chloris gayana L.; 0% inhibition), buffel grass (Cenchrus ciliaris L.; 8% inhibition) and siratro (Macroptilium atropurpureum (DC.) Urb.; 9% inhibition)] were the least affected in their root growth. These results suggested that parthenium weed is capable of interfering with the growth of neighbouring seedlings even at very early stages of growth. The response found for buffel grass may partially explain why this introduced pasture grass has been found successful in suppressing the growth of parthenium weed in the field

Managing an invasive weed species, parthenium hysterophorus, with suppressive plant species in australian grasslands.

AbstractParthenium weed has been invading native and managed Australian grasslands for almost 40 years. This study quantified the potential of selected plant mixtures to suppress the growth of parthenium weed and followed their response to grazing and their impact upon plant community diversity. The first mixture consisted of predominantly introduced species including Rhodes grass, Bisset bluegrass, butterfly pea and green panic. This mixture produced biomass rapidly and showed tolerance to weed species other than parthenium weed. However, the mixture was unable to suppress the growth of parthenium weed. The second mixture of predominantly native pasture species (including forest bluegrass, Queensland bluegrass, Buffel grass and siratro) produced biomass relatively slowly, but eventually reached the same biomass production as the first mixture 12 weeks after planting. This mixture suppressed parthenium weed re-establishment by 78% compared to the control treatment. Its tolerance to the invasion of other weed species and the maintenance of forage species evenness was also superior. The total diversity was five times higher for the mixture communities as compared to the plant community in the control treatment. Therefore, using the suppressive pasture mixtures may provide an improved sustainable management approach for parthenium weed in grasslands