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Keywords:

  • parthenium weed;
  • suppression index;
  • glasshouse screening;
  • weed management;
  • biocontrol;
  • growth suppression traits

Summary

Parthenium hysterophorus is an invasive weed in Australian rangelands. It displaces valuable fodder plants and causes significant production losses within the cattle industry. Glasshouse screening trials were used to test 20 selected fodder species (test species) for their suppressive ability against P. hysterophorus growth. The trials used two planting densities (four or six plants per pot) and five planting frequencies. Each density by planting frequency was replicated three times. The dry shoot biomass of the test species was used to calculate a suppression index, in order to rank the relative suppressive abilities of the test plants. Setaria incrassata, Panicum maxicum and Cenchrus ciliaris were ranked as strongly suppressive, while Astrebla squarrosa, Bothriochloa pertusa, Themeda triandra, Astrebla elymoides, Bothriochloa decipens, Eulalia aurea and Lablab purpureus were moderately suppressive. The other test species had only poor suppressive abilities. A second glasshouse trial assessed the growth characteristics of the test plants at 13, 27 or 40 days after transplantation (DAT). Test species that strongly suppressed the growth of Parthenium hysterophorus had several attributes that included the ability to attain a greater height, the rapid production of tillers or a branched canopy and an extensive leaf area and root system; these growth attributes were present as early as 13 DAT. The present glasshouse screening approach identified several fodder species for further testing in field trials, and because the attributes that allow the test species to suppress Parthenium hysterophorus are present at the earliest stages of the plant’s life cycle, a rapid screening method is proposed that assesses these attributes at 27 DAT.