Copper spray – the sterilizer?

While not wanting to be seen as anti-copper spraying of avocados, or on any horticultural crops for that matter, I feel pressed to discuss some of the negative effects copper has and will have on our orchards and the environment.

I am no tree hugger, but am hugely respectful of the delicate balance we have with nature and the necessity to pass our land and environment to the next generation. I mean we are really only guardians of "our" land for our lifetime and pass it on as we vacate the earth.

I also respect the AGA scientists and all those who assure us that copper is the only way to stop body rots, anthrax, nose and so on. However, during the Copper Road Show I was gelled into gear to do some research in this area, supported by a University educated in soil science under the eminent Professor Walker. Following the recent study tours of the world done by ASB it is clear the consumer is the key person. They want to know under what conditions and how the product was grown and processed. The consumer will increasingly demand to see the conditions under which their food is grown.

Soils are the earth's stomach, teeming with microorganisms, soils, bacteria, breaking down humus, mixing the soil and balancing what we throw on it.

If you look over the fence to some of the dairy farms, particularly in the Waikato, that have received excessive amounts of nitrogen, you will find run down yellow pastures that are not doing too well at all. One farmer stated he needed to apply 350kg of nitrogen just to maintain production and his farm was ravaged by clover flea. Not a good look. His soils would have been rendered toxic, with little humus, no worms or microorganisms.

Nature works at its own speed and more in the tank doesn't mean it will go faster. One quarter teaspoon of copper sulphate will kill you and half a cup will sterilise a 35,000L swimming pool.

So, does fruit absorb copper, making them toxic for human consumption? Two copper wires are often laid horizontally over the roofs of houses in Britain to kill moss and fungus.

The rain passes over the copper and makes a solution that washes down over the mosses. Excess copper will kill all invertebrates - those are the little fellows with no spine! Copper is so potent it kills spores, mycelia and microbes, not only the fruit trees and in the soils but in the shelterbelts as well. Liming and mulching apparently hold the copper in the top layer.

We are told that orchards sprayed regularly with copper will exceed levels satisfactory for residential housing development. Solution - it was suggested we could deep plough the toxic copper topsoil under. It is accepted that copper is held tightly into the top level of the soil. Perhaps all the soil could be removed and dumped before a housing subdivision is started. The question begs - do non-copper orchards produce better orchards? I understand copper has been used extensively in other crops and some research would be good there too.

In summary copper is a great steriliser, in fact there is nothing that will touch it, but is it sterilising our soil and environment? When the consumer demands to know the conditions our avo's are grown in, will they accept orchards with excess copper levels?

We need to look at all the issues and try to get a more balanced view on potentially dangerous elements. Remember it will be the consumer who will demand balance, integrity and best practice.


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