Biological control of Parthenium II: Allelopathic effect of Desmostachya bipinnata on distribution and early seedling growth of Parthenium hysterophorus L.

Field surveys conducted in Lahore and Sialkot Districts (Punjab, Pakistan) revealed that the allelopathic grass Desmostachya bipinnata restricts the spread of the noxious weed Parthenium hysterophorus. The study also showed that the frequency and density of P. hysterophorus was lower in D. bipinnata-dominated sites compared with nearby areas without D. bipinnata infestation. In laboratory bioassays, aqueous and shoot extracts of D. bipinnata at 5, 10, 15 and 20% (w/v) significantly reduced the germination of P. hysterophorus, with complete inhibition at the highest concentration. The extracts also inhibited root and shoot growth and reduced seedling biomass of P. hysterophorus. The shoot extract of B. pinnata was more allelopathic than its root extract.