The Wet Tropics Conservation Strategy sets out a strategic approach to weed control.
Most weeds are introduced deliberately for agriculture, horticulture, pastoral grasses, botanical collections aquaria, medicinal herbs or agrofirestry. The most cost-effective means of weed control is to prevent environmental weeds being introduced and to identify and eradicate any new weed outbreaks, particularly of species which can invade intact ecosystems. Identifying actual and potential weed sources is extremely important because prevention of weed introduction and eradication of new outbreaks is the most efficient and achievable means of control. Thus, weed management requires close cooperation with quarantine and customs services, WHA neighbours and community.
Weed control is often labour intensive, costly and requires long term management commitment. Eradication of extensive infestations is often impractical because of the time and resources required and the possible environmental impacts of control techniques such as biological and chemical agents and fire regimes. To be effective, weed control programs must be followed up with the revegetation of native plant species, and subject to ongoing monitoring. Weed mapping can be a useful tool to help manage outbreaks and identify potentially susceptible areas.
Historically, weed control has focused on established outbreaks of weeds which affect agricultural productivity. Funding has too often been short term and, consequently, control measures have been ineffectual in the long term. An Australian Government initiative has focused on environmental weeds which are currently becoming established in the Wet Tropics and have potential to overrun intact ecosystems, but where eradication is still achievable. Targeting new incursions of miconia species, mikania vine, Koster’s curse, Siam weed and limnocharis, the Australian and State Governments have provided $490,000 for the first year of eradication and guaranteed funding for five years.
Pond apple (Annona glabra) is a major environmental weed of the Wet Tropics bioregion of north Queensland and is designated as a Weed of National Significance (WONS). This small tree forms dense stands particularly in swamp areas. It prefers the silty alluvial soils of coastal flood plains and is primarily dispersed by water, especially when it floods. Disturbed flood prone ecosystems are the most at risk from pond apple invasion and it represents a very significant threat to many lowland riparian vegetation communities in the Wet Tropics. The seed of the pond apple tree can lie dormant for up to two years and still germinate, increasing its opportunity to spread.
In 2001 the Wet Tropics Management Authority received funding from the Natural Heritage Trust through the WONS program. Ian Holloway was commissioned as a consultant by the Authority to research pond apple in the Wet Tropics. The aims of the project were to:
The project report 'Adaptive Management: Pond Apple Control In the Catchments of the Russell-Mulgrave and Tully-Murray River Systems' is available below.