Weevils Wipe Out Killer Weeds In Papua New Guinea

July 14, 1998

In a move that could save the environment, village economies and even human lives, CSIRO scientists have wiped out 20 square kilometres of a noxious water weed infesting the Sepik River in PNG.

Researchers from CSIRO Entomology used tiny weevils as biological control agents to control a massive outbreak of the exotic Latin American weed, water hyacinth, that was threatening the river, the villages which depend on it and the natural environment of PNG.

The project, funded by AusAID, is a fresh triumph for Australia's "six-legged ambassadors" - tiny benign insects now saving crops, family livelihoods, industries and ecosystems around the Asia Pacific region.

Water hyacinth infestations clogging up the Sepik River wetlands were causing great hardship to people using the rivers and streams to move around the country - like a road network.

According to Mr Mic Julien from CSIRO Entomology, the release of biological control agents such as weevils dramatically reduced the areas covered by the weed.

"Over the past five years, we have released 450,000 weevils and reduced infestations from 27 square kilometres to just seven," Mr Julien says.

The Sepik River system is a major waterway in PNG. Water hyacinth was first recorded in the Lower Sepik River floodplain in 1984 and spread quickly, infesting many lagoons and hundreds of kilometres of river banks.

By 1991, large water hyacinth infestations were severely disrupting the lifestyle of villagers from the Middle and Lower Sepik who could only reach gardens, markets and fishing by using the waterways.

These infestations also resulted in the deaths of several people who were unable to reach essential services in time for life-saving treatments.

The government of PNG realised that it was neither desirable or practical to control the weed with herbicides and so alternative control methods were sought.

"Firstly, we needed to locate water hyacinth outbreaks and determine the extent of the problem," says Mr Julien.

It was found to be much more widely-spread than previously thought with infestations in about 250 locations.

The second aspect of the project was deciding what to do at each location and then doing it.

"A combination of biological control using the weevils, Neochetina bruchi and Neochetina eichhorniae, and some manual control was used," says Mr Julien.

"The weevils are reared both in Brisbane and PNG, and then either transported by air or boat to infested areas.

"You can see dramatic reductions of water hyacinth within five years of releasing the weevils. Lagoons and lakes which had been almost totally covered by the weed are now substantially cleared."

The project is led by CSIRO Entomology from its research centre in Brisbane in collaboration with PNG's Department of Agriculture and Livestock. The project operates from two locations in PNG, the project headquarters in Port Moresby and a regional base at Angoram, on the Sepik River.

AusAID PNG Program Officer, Mr Andrew Pope, says they are more than happy with the achievements of this project.
-end-


CSIRO Australia

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