Chemical, phytochemical and biological control of Parthenium hysterophorus L. in Pakistan.
Parthenium hysterophorus L. (parthenium) has been rapidly spreading and replacing the local flora in Pakistan for the last 20 years. Various studies were carried out for chemical, phytochemical (through allelopathic plant extracts), and biological control of this noxious alien weed. Two chemical herbicides namely ChwastoxTM and Buctril SuperTM were employed at recommended (R) as well as lower rates i.e. 0.75R, 0.50R and 0.25R. Buctril Super proved highly effective and all the employed concentrations killed the target weed within two days of spraying. In a phytochemical control study, aqueous extracts of different concentrations (2-10% w/v) of five allelopathic trees: Azadirachta indica (L.) A.Juss., Ficus bengalensis L., Melia azedarach L., Mangifera indica L. and Syzygium cumini (L.) Skeels, were evaluated for their herbicidal potential against germination and early seedling growth of parthenium. Extracts of all the test plant species were found effective in arresting germination and suppressing seedling growth of parthenium. Extracts of F. bengalensis and M. azedarach were found to be highly effective. So far no biological control agents for parthenium have been reported from Pakistan. Recently we found a Mexican beetle Zygogramma bicolorata Pallister feeding on parthenium. Furthermore, we also found very heavy infestation of larvae of an unidentified insect species feeding on the weed during the months of October and November 2005, resulting in complete death of the weed plants.