Biological control of weeds in the 22 Pacific island countries and territories: current status and future prospects

Abstract

Biological control of introduced weeds in the 22 Pacific island countries and territories (PICTs) began in 1911, with the lantana seed-feeding fly introduced into Fiji and New Caledonia from Hawaii. To date, a total of 62 agents have been deliberately introduced into the PICTs to control 21 weed species in 17 countries. A further two agents have spread naturally into the region. The general impact of the 36 biocontrol agents now established in the PICTs ranges from none to complete control of their target weed(s). Fiji has been most active in weed biocontrol, releasing 30 agents against 11 weed species. Papua New Guinea, Guam, and the Federated States of Micronesia have also been very active in weed biocontrol. For some weeds such as Lantana camara, agents have been released widely, and can now be found in 15 of the 21 PICTs in which the weed occurs. However, agents for other commonly found weeds, such as Sida acuta, have been released in only a few countries in which the weed is present. There are many safe and effective biocontrol agents already in the Pacific that could be utilised more widely, and highly effective agents that have been released elsewhere in the world that could be introduced following some additional host specificity testing. This paper discusses the current status of biological control efforts against introduced weeds in the 22 PICTs and reviews options that could be considered by countries wishing to initiate weed biological control programmes.

Spatial patterns of presence, abundance, and richness of invasive woody plants in relation to urbanization in a tropical island setting

“…Educational and economic constraints in Fiji could allow invasive species to become a much larger problem than they now are (Lenz et al, 2019 in press), which is a serious matter of concern, considering the rapid rate of exotic species accumulation in the Pacific islands (van Kleunen et al, 2015). Fiji has had some success with relatively inexpensive biological control for a limited number of invasive species (Day and Winston, 2016). When developing a list for prioritization the species' potential as a target for biological control as well as its harmfulness should be considered.…”

Site‐specific management is crucial to managing Mikania micrantha

“…In many parts of the Pacific and Asia, small landholders practise subsistence agriculture (Day & Winston, ). As such, the main method of weed control is typically slashing with hand‐held knives or hand‐pulling.…”

“…The suppression of M. micrantha by P. spegazzinii results in increased productivity through reduced competition and a reduction in time weeding or applying herbicides, thereby decreasing costs, time and potential environmental impacts (Day et al ., ). Due to its high specificity and its negative impacts on M. micrantha , P. spegazzinii is under consideration for further releases in both Asia and the Pacific in an attempt to help manage M. micrantha and decrease costs and time spent controlling the weed (Day & Winston, ; Day et al ., ).…”

“…Mikania micrantha is an ideal example of the importance of applying diverse management approaches, as it is found in a broad range of habitats across its invaded range (Zhang et al ., ; Kaur et al ., ; Day et al ., ). Mikania micrantha is now found in 20 Pacific islands and territories (PICTs; Day & Winston, ) and most countries in south and south‐east Asia (Day et al ., ).…”