Small weevil with a big job to do

LIVING in the driest continent on earth means that we need to be conscious of looking after our freshwater creeks, dams and reservoirs.

Some of the most serious threats to these are the insidious noxious water weeds which grow to dominate waterways.

The ‘fearsome four’ are Salvinia, Water Hyacinth, Water Lettuce and Cabomba …

Combating them once they escape (mostly from being illegally kept as aquarium plants) is difficult, expensive and can take a very long time.

Luckily, scientists over the years have found some helpful bugs which assist in keeping the first three floating water weeds (Salvinia, Water Hyacinth and Water Lettuce) under check, but Cabomba is a submerged weed and so finding a bug which works under the water has been pretty hard.

Ewen Maddock Dam at Glenview has a serious infestation of Cabomba weed growing under the water surface. It’s been there for well over 20 years and all efforts to get rid of it have so far failed.

It arrived in the dam in the early 1990s thanks to an infamous drifter who travelled up and down the coast, planting and spreading water plants into waterways so that he could later collect and sell them to support his itinerant and nomadic lifestyle.

Seqwater now spends over $170,000 a year in just three dams manually removing Cabomba in an attempt to reduce the problems the weed causes.

But now that may be about to change with some world-first research coming out of the lab and into the real world, thanks to the CSIRO and Seqwater.

After a 19 year search for a suitable possibilities and weeding out the ones that don’t cut the mustard, the CSIRO scientists settled on one tiny weevil which looked the goods.

For the last few years, they have been busy testing this weevil from Argentina, making sure that its appetite is for Cabomba, and only for Cabomba.

The lab trials have been a raging success and now, with the support of Seqwater, the bug is about to be let loose in the wild.

To start with, they’re releasing the weevil into Lake Kurongbah near Petrie, where Cabomba is rife. They’ll see how it deals with ‘the wild’ and then they’ll use the dam as a breeding ground where the weevil can be collected and shipped around the country to be released into other areas where Cabomba is a problem … like Ewen Maddock Dam.

This is a world’s first with no other country having such success with a biological control agent against Cabomba. If the weevil does its job, it will mean more and better quality water available in our dams, and less weed interfering with fish and wildlife living within them.

As responsible locals, we all have a job to play in protecting our waterways from noxious water weeds. Best advice is to only grow what is legally allowable, and never ever release anything into our lovely waterways.