Topic: Bordeaux mixture

[Marymary]

In 2004 & 5 I lost my entire tomato crop to blight, last year I grew mostly resistant varieties which did very well.  This year I'd like to try some more interesting varieties but am worried the dreaded blight will get them again.  I have heard about using Bordeaux mixture - I try to be as organic as possible but apparently this is considered ok.  Can anyone tell me when & how you are supposed to use it but, more importantly, if it works.

Thanks

MM

[raisedbedted]

Hi,

I also garden organically and wrestle with my conscience with Bordeaux.

If I do not use it then by August bank holiday its all over for the Toms.

Bordeaux is I believe based on Copper Sulphate and is not too bad as long as crop rotation is strict otherwise levels of copper sulphate can build up in the soil.  It works as a preventative rather than a cure and people often spray at 2/3 week intervals from about end June.  It does work to delay the onset but in my opinion wont stop it completely.  Still I'd rather ripen green tomatoes off on a windowsill than ingest dithane.

Bordeaux is 'ok'd by the soil association as organic, I suspect this is more to do with there not being an alternative.

I use it because after 3 years I still havent built a roof to keep my toms dry!

POW

[Mrs Ava]

I have a roof on my tom house, which really stops blight in it's tracks.  The toms I grow in the open will be blighty if I don't spray with Bordeaux.  It isn't a cure, it is a preventative.  I only spray 2 to 3 times and that has previously kept me blight free until September.  Then with the damper mornings and evenings, blight strikes quickly.

I don't know how organic or not it is, what I do know is without it, I would loose my important tomato crop.

[BAK]

fyi - see the following topic on blight

http://www.allotments4all.co.uk/joomla/component/option,com_smf/Itemid,91/topic,28410.0

Marymary - I am interested to know what your resistant varieties are.

[philcooper]

Bordeaux is 'ok'd by the soil association as organic, I suspect this is more to do with there not being an alternative.

The SA is a commercial growers' organisation. The equivalent for amateurs is Garden Organic (previously HDRA) which has Bordeaux at the lowest level of acceptability - ie use it sparingly and only if you must becuse of the danger of soil contamination.

Having said that, it does work by providing a physical barrier to the fungus which is trying to grow on your tomato/potato. But, because it is a physical barrier, you need to respray whenever it is washed off (this can be a frequent event). You also need to remember to wash the tomatoes thoroughly before eating

Phil

[OllieC]

I used to spray once a fortnight from mid summer onwards (and also after rain) but the Blightwatch website gives you a warning & last year I only sprayed when it notified me that there was a risk. It worked.

I've been told that Copper Sulphate is essential for a couple of cancers to develop (albeit in very small amounts). It's possible that we're exposed to enough of it already so increasing exposure mght not have any effect. But I've rinsed all that bit more thoroughly since hearing this!

[tim]

What puzzles me is how the copper can pollute the soil, absorbed through the leaves, without making the tubers - through which it must go - lethal??

Eyes shut, we're still here after 45 years of use!!  But don't quote me.
And it does not always save you!!

Like Emma says - protection, protection.

[philcooper]

Tim,

It isn't absorbed through the leaves it sits on the surface, which is why it is "organic".

The absorption from the soil is at such a very low level (because the levels in the soil are at a low level) that it is "not a problem", but it is the pollution of the the soil which means that the SA and GO are not wildly enthusiastic about it.

Phil

[OllieC]

Do SO etc look at residue levels on products to be consumed or do they purely focus on what chemicals are used and what the effect is on the surrounding environment?

I recently saw a sign advertising "Organic Veal" which got me thinking about animal welfare and questioning what you can get away with whilst still being organic.

[jennym]

As Phil says, the Soil Association is a commercial organisation, here's an example of comments on residues: http://www.soilassociation.org/web/sa/saweb.nsf/45663f98fc3fd56580256a9300536789/048abbec67685ce480256f5c00353312!OpenDocument
There was an interesting interview on either Farming Today or The Food Programme on Radio 4 not so long ago about organic veal, and to be honest, in my mind, if the lady was to be believed, then there is a lot of good work being done in order to use the surplus male cattle in the best possibel way whilst supplying a commercial demand, so if the Soil Association are part of that, then all praise to them. A link here: http://www.helenbrowningorganics.co.uk/the_good_veal_guide.phtml

[tim]

That's the bit that fazes me, Phil - when I spray, it goes onto the leaves.

[Marymary]

Hi BAK - the resistant varieties I grew last year were Nimbus & Fantasio - both cropped well & tasted good.  This year I am growing those & have also ordered ferline & legend from T&M.  I am growing other varieties too but if the dreaded blight does strike I should have something to harvest.

POW - what's dithane.  ???

Thanks for all the really good advice here.  One final very basic question - how do you spray?  With one of those spray bottles or with something more industrial?  I should imagine that with the amount of toms some people here grow spraying with a little sprayer would take some time. Also is it necessary to get every leaf front & back & finally  :) what about the flowers?  Does it matter if they get sprayed? 

Thanks again

[tim]

I use a 2l Hozelock with lance - essential for getting under the leaves as well

Flowers? Never thought about it. With potatoes, no problem I would think. Toms - I would avoid?

I keep the big lever pump one for nasty things!

[redimp]

Last year I trialled using compost tea from a watering can - it is supposed to increase bacterial activity on the surface of the leaves which fight off blight.  It seemed to work but will always spray after harvesting tomatoes - not before :-X and Lincs does not appear to be especially Blight prone - not as humid as the rest of the country.  One thing it is though is completely chemical free.

[tim]

Interesting. Spray after harvesting? Why then??

[BAK]

marymary,

I grew Fantasio and did a little experiment, spraying some plants with copper sulphate but not others. The sprayed plants were ok but the unsprayed ones succumbed in mid-Sept, albeit about 2 weeks after everybody else on our site complained that they had blight.

I have grown Tamina for 4 years or so, and find that it seems to be more resistant than most other varieties, although I do spray it.

I agree with others who have indicated that it thrives in damp conditions. In some drier summers it does not appear where we are (Sunningdale in Berks).

Finally, I aslo agree that the potato blight watch service is a good thing to keep your eye on.

[kitten]

I aslo agree that the potato blight watch service is a good thing to keep your eye on.

Where can we find this blight watch please?  Might come in useful...

[redimp]

Interesting. Spray after harvesting? Why then??

Cos the noxious stinky stink is impossible to wash off - so pick toms, spray plant.  Sorry if it was a bit unclear :)

[aob9]

Somebody asked about Dithane. The active ingredient is mancozeb (EBDC type Pesticide). It has been used commercially and by home growers for years. It was reviewed in the U.S recently and was given approval for continued use for Blight and many other diseases in edible crops. According to the pesticides safety directorate (UK), it is licensed for use until 2013. Another ingredient used to control blight commercially is Metalaxyl. Unlike Dithane and Bordeaux mixture metalaxyl is absorbed by the plant ( systemic) to provide protection from within and is always used as part of a blight prevention program( i.e it is sprayed at regular intervals during the growing season).

I worked in commercial growing for years and used plenty of both these compounds. I now grow my own fruit and veg at home and would stay away from them both if possible( in fact metalaxyl is not available for private use).

Last year I grew some of my tom's outdoors and was very lucky not to get any blight at all. I hope all goes as well this year.

[BAK]

http://www.blightwatch.co.uk/content/bw-Home.asp but you have to register at http://www.potatocrop.com/content/default.asp to be able to use it.