While the purple petals of the thistle may evoke dreams of home in a Scot; to Australian farmers they are a nightmare. Here, as in Europe, the thistles cast a beautiful mauve haze o' the glen, but they also damage the eyes of cattle and burrow into sheep's fleece. But these wee chappies are helping to solve the problem.

In Mediterranean Europe, where the thistle originates, there are plenty of natural enemies to attack, and keep it under control. So Australia's CSIRO, teamed up with livestock and wool producers to invite some special thistle-eating weevils to immigrate.

"These insects are fairly long lived. They live for about a year and they only lay eggs once a year and that's when the plant's in flower. The eggs hatch quite quickly and within 6 weeks the head dries off and the insects come out. But in the middle of that six weeks, the larva develops inside the head, chomping on the tissue doing quite a job of killing the seed."

CSIRO also found a weevil that dines only on the stem of the thistle. After stringent testing, to ensure they were safe for the Australian environment, the weevils were released on the thistle nuisance.

The weevils have been so content munching on their favourite food, that their numbers have rapidly increased. It's meant that, combined with other types of weed management, the weevils are helping to greatly reduce the thistle problem.

Bill Petitt
Black Mountain Laboratories Clunies Ross St
Black Mountain Act 2601

Bill.Pettit@criba.edu.au