Under The Microscope

ALTERNATIVES TO THE CHEMICAL CONTROL OF WEEDS, edited by Bassett, Whitehouse & Zabkiewicz; FRI Bulletin No 155 1990; 159 pages; $40 plus GST

We've all seen the ads with David Bellamy stomping through the bush asserting that "Old man's beard must go!" What he doesn't say in those 30-second shots is how we are to get rid of the nasty weed that's strangling our native forests.

That's a problem with which DOC, the Forest Research Institute and a host of other organisations and individuals are struggling. This FRI bulletin is a compilation of presentations on the subject made at an international conference in 1989. The cover gives a good idea of the non-chemical approaches within, showing gorse under attack from rollers, goats and spider mites.

It's easy to see that there is no simple solution. Stock grazing techniques are recommended by one paper as useful for control of forest weeds. Another shuns them as a means of spreading yet more weed seeds, as well as encouraging the creation of weed-prone clearings. Weed control using insects has a 30% success rate -- better than some herbicides. It also raises a host of issues associated with the introduction of potentiay new pests.

I was interested to note that the homeopathic approach, apparently discussed by one participant, was deemed "insufficiently convincing to the scientific fraternity" and so not included in the formal presentation.

The collection doesn't present an answer to the growing weed problem, but it does point the way towards potential strategies. Even David Bellamy can't ask for much more.

Cathryn Crane, NZSM