[Trillium]

I just read a garden blog from Germany where this lady also encountered blight on her toms and potatoes and she used this organic blight spray with very good results. The secret is to either do a preventative spray every week and after every rainfall, or, if you see the first signs of blight, spray daily. Be sure to keep spraying both the upper and under sides of leaves until harvest is finished. She found that in a few days the plants perked up and gave her good yields - because she kept spraying. It was a nuisance for her to spray so often but she did get good toms which is always worth the effort.

1 gallon water
1 tbsp baking soda
2-1/2 tsp vegetable oil

Put into a spray and shake well. Spray, and shake container often to keep ingredients blended.

[Iain@JBA]

I wonder if that would work on a commercial scale because it would save me a fortune.
I was reading tonight about putting cloche tents over your potatoes and tomatoes. This keeps the leaves dry and prevents the spores from generating.

[realfood]

If it works, I wonder how it prevents blight? I can see that the dispersed vegetable oil on the leaves, would help to shed the rainfall which could be infected with blight spoors. I wonder what effect the  baking soda has on preventing blight?
There has been comment in the past about the use of a spray made from full fat milk diluted with 10 times its volume with water, as an anti-blight spray. I did try this spray last year on potatoes, but was unconvinced as to its efficacy.

[mumofstig]

water and milk spray is usually used on leaves with powdery mildew 

[Trillium]

This spray, according to the German blog gal, will also work on powdery mildew. I believe the key is that the baking soda is alkaline, which blight doesn't like. The oil would help the solution to stick while the water would be the dispersing item. She indicates it wasn't the be-all-end-all solution but it certainly removed a lot of her blight and allowed the crops to grow. If you have to deal with blight and mildew, a fairly good solution should make a lot of difference, so I hope it helps those in need 

In commercial application, I don't see why you couldn't try a test patch. I imagine the bouncing about of the sprayer should keep the mixture blended. I'm sure there are stabilizers which could be added, but no point gilding the lily and complicating a simple formula.

[Iain@JBA]

I can just see my pictures in the Scottish farmer magazine now when I show them my new blight prevention mix. If it came through the spray jets it would be great, but do I really want to risk it. I could sell all my spuds as organic.

[Trillium]

Like I mentioned, a small test patch this year should give you the answers you need Iain

[solway cropper]

Several studies have shown that sodium bicarbonate is effective in the treatment of powdery mildew but I'm not sure how it would work with blight. If something so cheap can be shown to be effective against blight it would upset the agrochem industry 

[SG6]

Trillium, please this is just me being as difficult as possible, but it does indicate the often strange happenings of this forum. But some time back I posted on a thread saying that there had been for some time the habit of people adding detergent in the form of washing up liquid to water to kill off aphids. The soap destroys the aphids waxy covering and so kills them. I think it concerned roses, I think my point was that although seemingly common I wondered what the damage to the rose was since it doesn't rain soapy water (usually).

I was jumped on by mods as it seems there is an EU "directiuve" or whatever that people CANNOT go round making up their own mixtures and applying it to the ground and plants in any form.

Now we have a post by a mod saying here a mixture to make up and spray.

[mumofstig]

I may be wrong (I often am!) but I think that sprays that are used as preventatives like garlic sprays etc are not covered by the regulations. It is only when you say that a spray is a pesticide or fungicide that you run into trouble.
Someone will be along to put us right soon no doubt

[Trillium]

Point well taken. However, the mixture I suggested doesn't include liquid soap. It recommends vegetable oil. True, it doesn't rain vegetable oil but you need something to make the mixture stick and this is relatively harmless considering the very small quantity used over any given time and that it's less harmful than the surfectants used in liquid soap.

I recall the government directive, but personally I wasn't sure about it and didn't emphasize it, particularly as it doesn't apply to me in Canada. I honestly believe that if you're using harmless food ingredients to protect your food crops, then there shouldn't be a problem. I could be wrong in this, but one has to do something to combat the continually encroaching diseases affecting one's garden. And newer, more powerful chemicals aren't the way.

Everything is open to interpretation, and it's possible that this new directive was interpreted in a different way than was originally intended. You certainly couldn't go around marketing such a product, but for personal use on an allotment, it's decidedly a whole lot safer than the chemical garden warfare formerly sanctioned by the government.

That's my opinion.

[PAH48]

That sounds a good idea to me...certainly worth a trial...
This year I'm planting 5 varieties, therefore if I only trial it on one lot....
Well! its worth a go...Cheers Trillium....