DISTRIBUTION AND SOCIO-ECONOMIC IMPACTS OF Mikania micrantha IN PAPUA NEW GUINEA AND FIJI AND PROSPECTS FOR ITS BIOCONTROL

Mikania micrantha or mile-a-minute is a fast growing Neotropical vine found throughout much of Asia and the Pacific, invading small subsistence farms as well as plantations. In 2006, a biocontrol project, funded by the Australian Government and managed by the Queensland Government, commenced in Fiji and Papua New Guinea (PNG). To help plan activities and determine possible benefits from the project, the distribution, growth rate and socio-economic impacts of M. micrantha were determined before the importation of biocontrol agents. Mikania micrantha was recorded in all 15 lowland provinces in PNG and on all major islands in Fiji. Plants grew up to 1 m/month in PNG and about 0.5 m/month in Fiji. A socio-economic survey (of over 380 respondents in over 230 villages from 15 provinces in PNG) found that 79% of respondents considered M. micrantha to be a serious weed, with over 40% considering M. micrantha reduced their crop yield by more than 30%. About 44% of the respondents had over a third of their land infested with M. micrantha, which they spent 1-2 days per fortnight weeding. About 85% of respondents controlled M. micrantha by physical means, such as slashing and/or hand-pulling. In Fiji, M. micrantha infestations were less problematic than in PNG. There were 52 respondents from four islands, of which over 60% considered M. micrantha a serious weed, losing about 30% of potential crop yield due to the weed and 33% reported having more than 30% of their farm lands infested. Only 15% of respondents needed to weed fortnightly, with 56% using slashing and/or hand-pulling as the main means of control. Nearly 90% of respondents used M. micrantha as a medicinal plant to treat cuts and wounds. To help control the weed, the rust Puccinia spegazzinii was imported into both countries, following host specificity testing by CABI in the UK, and subsequently released widely. Initial laboratory trials and monitoring at a few sites, found that the rust can significantly reduce the growth of M. micrantha and offers great potential for the control of this weed in Fiji and PNG and other countries where M. micrantha is a problem.