Environment

Australia is using an imported insect to control an imported weed

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The cabomba weevil feeds on nothing but the cabomba plant, throughout its whole life
CSIRO
Scuba diving in a cabomba-filled lake doesn't look like much fun
CSIRO
The project is claimed to mark "the first release of a biocontrol agent against cabomba anywhere in the world"
CSIRO
The cabomba weevil feeds on nothing but the cabomba plant, throughout its whole life
CSIRO
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What do you do if a South American weed is choking up your local Australian waterways? In the case of the cabomba plant, scientists are enlisting the help of the weed's natural South American enemy, the tiny cabomba weevil.

Cabomba (Cabomba caroliniana) originally came to Australia in 1967 as an aquarium plant, and has since spread throughout lakes and rivers along the country's east coast. It grows up to 5 cm (2 in) per day, forming clumps that displace local flora and fauna, block sunlight from reaching lower depths, add to the cost of water treatment, and make boating or other recreational activities difficult if not impossible.

Large quantities of the weed are currently removed from water bodies by mechanical means, although doing so is an expensive and laborious process, plus the plant quickly grows back to problematic levels. With these limitations in mind, scientists from the Australian national science agency CSIRO looked to the cabomba weevil (Hydrotimetes natans).

Native to several South American countries, the aquatic insect is only about the size of a grain of rice, and takes its name from the fact that it feeds on nothing but the cabomba plant.

That said, in order to be on the safe side, the CSIRO scientists raised three generations of the weevils in captivity, offering them 17 Australian aquatic plants that are closely related to cabomba. The weevils showed no interest in those other plants, choosing to feed only on cabomba throughout their whole lives.

The project is claimed to mark "the first release of a biocontrol agent against cabomba anywhere in the world"
CSIRO

An imported batch of the weevils were initially kept in quarantine, and individually inspected for parasites and pathogens. Having passed that inspection, they were then bred in captivity, producing a population that was recently released into the cabomba-infested Lake Kurwongbah, north of Brisbane.

Time will now tell how effective the insects are at controlling the weed. In the meantime, more of the weevils are being bred for use in other lakes.

The project is funded by water company Seqwater, and by the Australian Government Department of Agriculture, Fisheries and Forestry. Leading the research are CSIRO's Dr. Kumaran Nagalingam and Seqwater's Dr. David Roberts.

Source: CSIRO

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7 comments
Dave Holland
Hmmmmm…. The article implies that, given a choice, the weevils will choose cabomba over other plants found in the water. That misses a critical consideration. If they are effective at consuming most (if not all) the cabomba such that there is insufficient cabomba to feed the weevil population (or if they end up in waterways that don’t have cabomba), the weevils have to decide do they eat a different and less attractive plant or do they decide to die instead. Which will they decide? It appears that all the tests done were where they have a choice that includes cabomba. Living things tend to adapt...
Claudio
releasing an alien insect in an enclosed environment infested by an alien plant? what could possibly go wrong?
Brian M
Dave Holland's (below) anyone reading the article must also immediately also see the problem he is describing.
Hopefully this is just an editorial mistake by the Press officer at Seqwater/Australian Government or its going to be another own goal by Australia.

They have of course plenty of experience in this sort of environmental mess up!
Bruce Bensetler
Suggest the book "Feral Future" by Tim Low for anyone interested in the sad history of invited and uninvited pests in Australia. A truly terrifying history of biological and bureaucratic disaster.
Bob Flint
Ask yourselves, how did this weed first get there, now introducing another link on the food chain, what do we suspect might happen then, non native fish, or reptiles, going up the food chain, nature will evolve. Will we ever understand?
CarolynFarstrider
The history of this type of alien introduction is not good. Evidence suggests that adaptation to new uncontrolled circumstances creates new problems. When they run out of weed, they will undoubtedly start on something else, even if it is less palatable. This way, (further) ecological disaster looms.
CorV8tor
So, what is keeping the weevil population in check? Grass you say? I say MFG! I hope it isn't relying on the depletion of the grass? H...y S..T Again with that importing alien's?