The status of weed biological control in Vanuatu

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The status of weed biological control in Vanuatu

Biological control of weeds in Vanuatu began in 1935, with the introduction of the tingid Teleonemia
scrupulosa to control Lantana camara. To date, nine biological control agents have been intentionally
introduced to control eight weed species. Seven of these agents have established on their respective hosts
while an eighth, Zygogramma bicolorata, an agent for Parthenium hysterophorus has only recently been
released and establishment is unlikely. The fate of a ninth agent, Heteropsylla spinulosa, released for the
control of Mimosa diplotricha is unclear. Six other biological control agents, including Epiblema strenuana
which was first detected in 2014 on P. hysterophorus on Efate have spread into the country unintentionally.
Control of the target weeds range from inadequate to very good. By far the most successful agent has
been Calligrapha pantherina which was introduced to control Sida acuta and Sida rhombifolia. The beetle
was released on 14 islands and managed to spread to at least another 10 islands where it has effectively
controlled both Sida spp. Control of the two water weeds, Eichhornia crassipes by Neochetina bruchi and
N. eichhorniae and Pistia stratiotes by Neohydronomus affinis, has also been fairly good in most areas. Two
agents, T. scrupulosa and Uroplata girardi, were released on L. camara, and four other agents have been
found on the weed, but L. camara is still not under adequate control. The rust Puccinia spegazzinii was first
released on Mikania micrantha in 2012 and successfully established. Anecdotal evidence suggests that it
is having an impact on M. micrantha, but detailed monitoring is required to determine its overall impact.
Future prospects for weed biological control in Vanuatu are positive, with the expected greater spread of
recently released agents and the introduction of new agents for P. hysterophorus, L. camara, Dolichandra
unguis-cati and Spathodea campanulata.