Skip to main content


Rethink required with resistance to herbicides

There have been some, shall we say, lively letters to ‘The Editor’ about poisons, in this instance 1080.
 |  Malcolm Campbell  | 

It has now been in use for over fifty years and 1080 has not been successful in eradicating any pests except on some isolated small off-shore islands. The evidence available now shows that over time, the target pests develop resistance to the chosen chemical requiring the development of even more potent chemicals to remedy the situation. A number of farm magazines have had articles very recently lamenting the evident fact that farm animals, cattle and sheep and others are carrying internal parasites, that have developed some form of immunity to the current drenches and the said drenches are becoming more and more ineffective.

The same resistance is now showing up in the use of ‘herbicides’ where the weeds are not being slaughtered in a way the users of these chemicals had hoped for. Indeed, an astonishing statement revealed that the search is on for herbicides effective against, of all things, ‘ryegrass’ one of the basic plants in NZ pasture. Zillions have been spent on research to develop more nutritious, more palatable, more drought tolerant and more vigorous ryegrass, and now we want a poison to kill it. Hard to believe, but true.          

Back to the 1080 poison, bearing in mind that poisons do not have a good track record anywhere. There are some very real weaknesses. Firstly, the target pests listed are possums, mice, rats, weasels, stoats, ferrets and cats. The possums, rats, mice and even birds are likely to eat the pellets. However, cats, weasels, stoats and ferrets are more likely after a carnivore type diet with some form of fresh kill favoured. Therefore the 1080 is a secondary poison via dead rats and mice to tempt the cats, weasels, stoats and ferrets. These critters may or may not be tempted. Another problem is that owls may eat a mouse that has been poisoned. A rethink is required to solve a very difficult question. No doubt it is a deadly poison and has according to the internet, widespread support from numerous organisations.

However, in most situations, there are usually alternatives. Why have no prizes been offered for new methods for the control of these pests? Two ladies in Waihi are interested in developing a group called Predator Free Waihi to tackle pest problems in the Waihi Area.  Most of the problem zones on the Coromandel Peninsula are bordered by farmland and trapping is not too onerous a task if enthusiasm could be generated in the farming community. There is an expression, ‘the world’s perfect mouse trap is still to be made’.

In my own case I began trapping for cats using rabbit pieces. Problem number one, I could only trap in the winter because the bait became putrid in the summer. My neighbour Neil Walker (he traps too) told me to use cat pellets. Problem number two – mice ate the cat pellets so the pellets have to be ‘shielded’ in a way that the odour is attractive to the vermin but unavailable to eat. There is room for improvement to the world’s perfect trap and collectively, we need that improvement.