Interference potential of the perennial grasses Eragrostis curvula, Panicum maximum and Digitaria eriantha with Parthenium hysterophorus
Van Der Laan, M.
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The successful invasiveness of Parthenium hysterophorus (parthenium) is attributed to its competitive ability and high allelopathic potential. The compound, parthenin, has been implicated as a major allelochemical in the plant. A field trial was established in Kruger National Park (South Africa) to investigate the inter ference between parthenium and 3 indigenous grass species, namely: Eragrostis curvula, Panicum maximum and Digitaria eriantha. Grass seedlings were transplanted from a glasshouse into field plots after failure to establish the seed in situ. Parthenium seedlings were introduced at densities of 5 and 7.5 plants/m2 from areas adjacent to the fi eld trial. P. maximum displayed best overall growth performance and was able to completely suppress parthenium growth with time. The other 2 grass species performed less favourably, in terms of both growth rate and ability to suppress parthenium. The ability of P. maximum to interfere effectively with parthenium growth indicates that this species has good potential for use as an antagonistic or rehabilitative species in containing the spread of the weed. In a laboratory study, seeds of the 3 grass species were exposed to pure parthenin in a germination bioassay. Based upon germination and early radicle development, E. curvula was the least sensitive and P. maximum the most sensitive to parthenin. Therefore, if P. maximum was to be used in a control or rehabilitation program, it might be difficult to establish P. maximum stands from seed in areas already infested with parthenium. While transplanting seedlings of the grass would avoid the seed germination problem and give the grass a head-start, the practicality of this method on a large scale is open to question.