An organic alternative to fungicides ....

[bearded bloke]

^^^^ ere we go ................

A copper pesticide is a copper compound used as a pesticide or fungicide. In the UK the Soil Association (one of the organic certification authorities) permits farmers to use some copper fungicides on organic land used for the production of certified organic crops only if there is a major threat to crops. [1] During the 2008 growing season the compounds were applied to much of the organic potato crop to control potato blight (Phytophthora infestans).[2] The compounds permitted are copper sulfate, copper hydroxide, cuprous oxide, copper oxychloride, copper ammonium carbonate (at a maximum concentration of 25 g/l), and copper oxtanoate. According to the Soil Association the total copper that can be applied to organic land is 6kg/ha/year.[3] This limit is designed so that the amount of copper in the soil does not exceed the limits specified in the Soil Association standards for heavy metals. Such copper compounds can build up in the soil and in excessive concentrations cause liver, kidney and blood disease.[4]

EDIT: forgot ........... taken from .... Copper pesticide - Wikipedia, the free encyclopedia

[Olorin2001]

So how much copper wire, tube or pipe do you have to hang up, drape over and generally spread around before you get a build up in the soil to dangerous levels. I understand that areas around old copper mines are toxic sites, and yet copper is an essential trace element for plants- as is sulphur, so it's all relative. Humans need about1mg/kg daily to ensure good health. And if your not going to spray Bordeaux mixture then you had best dig up those railway sleepers, telegraph poles and check the label of any wood preservatives you have been using.

[Olorin2001]

I just loved the phrase - theoretical organicness - makes me wonder how much of our food that is labeled organic, is actually only organic in theory - thankfull I know what goes into my allotment grown food, and as I have had it for twelve years I don't worry about what the last occupant did, but should I worry though?

[Nicos]

My thoughts on trying out something a bit different was because, it seems, that every time I have sprayed plants with Bordeaux mixture it promptly rains and washes it all off

The thought of a piece of copper wire would mean less spray, and ,which would work after it had rained! Much less work involved!
..well that's the theory- I just wondered if other peeps had tried it

[Olorin2001]

You could try it with half your tomatos and half of the tatties, and spray the others, maybe leave some untreated if you really want to see what effect your having by treating in any way.
I read somewhere that for blight spores to germinate requires a high enough temperature and humidity for two days, and that commercial farmers have alarms systems to warn them that the critical point had been reached - maybe there is a national or area hotline in existance?

[Bren In Pots]

I read somewhere that for blight spores to germinate requires a high enough temperature and humidity for two days, and that commercial farmers have alarms systems to warn them that the critical point had been reached - maybe there is a national or area hotline in existance?

There is its called Blightwatch anyone can join for free, they send you email notifications of Smith periods for your area :-

Blightwatch.co.uk - the essential service for professional potato growers

[bearded bloke]

So how much copper wire, tube or pipe do you have to hang up, drape over and generally spread around before you get a build up in the soil to dangerous levels.

Not a clue,sorry.Knowing of the toxicity of copper did not come from gardening but from painting,a little oblique but there you go when I lived at the seaside I would occasionally get called to paint yachts below the waterline with "cruising anti-fouling" which was traditionally copper based.For most of the 1980's it was banned & a butyl based product was used,as there were ecological concerns for the impact on micro-organisms caused by the copper content of the paint washing off (particularly while at anchor or moving very slowly in shallow water),after the survey the general consensus was there was no perceivable threat,but I believe it is still in force in parts of Scandinavia & the inland waterways of Holland.