Blight - is it worth spraying?

[Granny]

Hi Chantal,
The thread on Ferline that you're referring to could well be mine - 'another tomato problem.' They're not showing signs of blight yet, even though my potatoes have got it, just this stunted look. In the last couple of days in the sun they seem to have picked up a bit. If anyone's interested I'll keep you posted on sun/growth ratios and blight progress!
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Granny

[oldherbaceous]

Dear Granny, we are always interested in what you have to tell us so yes please, do keep us posted.

[Cider Boys]

For what it’s worth my take on blight is as follows:

SPRAY, SPRAY and SPRAY.

Some varieties of potato are more resistant to some forms of blight than others but, in my opinion, there is no such thing as a blight immune potato.

You can not cure a blight infection by spraying. Spraying only helps prevent a blight attack by shielding the leaves from the blight spores.

If you get blight (and you usually will at some stage) remove all the haulm and burn it. Leave the tubers in the ground for a couple of weeks to form a thicker skin then lift on a dry day. As long as the blight spores have not reached the tubers they will be ok. If any have been blight affected they will rot in storage and although the blight will not spread the soft rot will cause unaffected tubers in contact to also rot.

So watch out for ‘smith’ periods (wet, humid and warm conditions) and SPRAY. Ideally you then spray every couple weeks or so, especially in damp weather.

(Forget about organic methods, they also spray, spray and spray; the hypocrites.)

We started lifting our Pentland Javelin this morning (not a patch on Maris Bard for taste IMO) and they had a touch of blight on some leaves.

We spray with a product called Tattoo by Bayer agricultural chemicals.

Barney

[Tigger]

I've had some blight on the early potatoes and I've cut off the leaves. The spuds are fine. Nothing on the main crop or outdoor tomatoes as yet.

I won't spray them. I'd rather extend the season by planting replacements in the tunnels. If I want sprayed crops, I can buy them on the market or in the local stores - which I won't.

[Johnboy]

Hi Tigger,
So I take it from your posting that you are self sufficient in Potatoes then?
That's quite an achievement!! Well done!!
JB.

[alan refail]

I think what Tigger means is that she doesn't grow her own produce just to spray it with propamocarb-hydrochloride and mancozeb.

Johnboy
Is it difficult to be self-sufficient in potatoes? I manage it despite guaranteed blight and no spraying. OK we bought some early Jersey Royals for a few weeks in late May and early June, but that's all.

Barney
"(Forget about organic methods, they also spray, spray and spray; the hypocrites.)
Well you would say that wouldn't you. Just because you say it doesn't make it a fact.

Alan

[Cider Boys]

Hello Alan

Well I can assure you that all commercial organic potato growers spray exactly as I do, in fact they grow their potatoes exactly as I do; we for years no longer add mineral fertilisers but that’s another story.

I would be very interested if you could find evidence of an organic commercial potato grower that does not spray against blight. The SA would be very interested in their methods because as one ‘organic’ and honest potato grower once stated there is no such thing as an organic potato since they ALL spray with chemicals. So if there was any justice the SA would concede that the term organic as defined by them should NOT apply to their potatoes.

Barney

[Tigger]

Hi JB - I'll grow sufficient potatoes outside this year to take me well into the winter and I'll have a few potted up in the tunnels for Christmas, then some more in there for Easter. We don't eat them everyday as we also have rice, pasta, noodles, etc., so it's not too difficult.

If we do run short, I've got a neighbour who grows far more than me and I can always buy some from him. He's a retired farmer. Having grown veg commercially for the supermarkets, he definitely doesn't spray anything he now grows for himself!

[Cider Boys]

What on earth are some people advocating on this forum – that we should not spray against blight?

Alan takes his predictable swipe at me; I will wait but will not hold my breath until he supplies evidence that commercial organic potato growers do not spray against blight.

I also garden and normally do not spray against blight on my garden potatoes and tomatoes but it would be highly irresponsible not to spray against blight on my commercial potatoes. Blight if not guarded against has the potential to ruin a country’s
potatoes (remember the Irish disaster) so all commercial potato growers are certainly spraying to prevent blight irrespective of being organic or conventional.

Once again science and facts are ignored to uphold the holier than thou organic argument!

Is anyone seriously arguing that hectares upon hectares of this country’s potatoes should be left for blight to decimate?

As for Alan’s jibe, at least my chemicals remain on the leaves unlike the copper that the wonderful organic SA spray on their potatoes.

Perhaps reading the facts from the exert below may enlighten those with rose tinted glasses.

ROYAL COMMISSION ON ENVIRONMENTAL POLLUTION
--------------------------
PESTICIDES STUDY
--------------------------
held in
The Old Library,
Sydney Sussex College,
University of Cambridge,
Cambridge
on
Thursday, 3rd February 2005
------------------
Committee Members
SIR TOM BLUNDELL
(Chairman)
PROF. JEFFREY JOWELL DR. IAN GRAHAM-BRYCE
PROF. JANE PLANT DR. SUSAN OWENS
MR. JOHN SPEIRS PROF. PAUL EKINS
PROF. ROLAND CLIFT PROF. BRIAN HOSKINS
PROF. STEPHEN HOLGATE
MR. D. HAMZA GOODACRE (Secretariat)
DR. CHARLOTTE GREY (Secretariat)
DR. DIANA WILKINS (Secretariat)
MR. TOM EDDY (Secretariat)
MISS. PHILIPPA POWELL (Secretariat)
DR. JONNY WENTWORTH (Secretariat)
--------------
(Transcript of the Shorthand Notes of Marten Walsh Cherer
Ltd., Midway House, 27/29 Cursitor Street, London EC4A 1LT.
Telephone: 0207-405 5010. Fax No: 0207-405 5026.



people are not using so much acid at all.
PROF. PLANT: With all of this application of chemicals, how on earth does anybody manage to produce potatoes organically? The supermarkets are full of supposedly organically produced potatoes.
DR. KIFT: Organic potatoes -- I am rather glad you brought that topic up -- get very regular fungicide applications of copper sulphate. Of the compounds that go on against blight, that is one of the very few where the active ingredient, the copper, actually goes onto the potato. A lot of the other blight sprays actually stay on the leaf and do not contaminate the potatoes, but copper sulphate is one where it does. Organic growers ring me, who grow broccoli and things, saying that they go in every week with a BT spray for caterpillar pests ----
PROF. PLANT: A BT spray?
DR. KIFT: Bacillus Thuringiensis. They are crystal toxins which are produced by a species of bacteria.
THE CHAIRMAN: They are natural.
DR. KIFT: Exactly. They are a natural toxin and, as such, the Soil Association thinks that that is fine. The important thing is that that will be applied every week to stop caterpillar damage to the crop and also they will go in and spray surfactants. They are called soft soaps. Essentially, you spray washing-up liquid, or some people do, on a very big scale. They go in and do that every week for each of those treatments, plus fungicide treatments, basically, including copper. So if you are talking about vegetables and potatoes organically, you have to use these products. Last weeks Farmers' Weekly is a good example. A Soil Association conference took place and there was a write-up of it. Quite a lot of it was devoted to how we can control blight on potatoes organically. Their target is to reduce the amount of copper applied per hectare from about 8 kilos to about 6, which I think is a lot of active ingredient.

With respect

Barney

[Colin_M]

Gosh, another hectic thread here! It sounds like "spray" can mean several things, depending on the fine details.

Barney, you seem to be saying that although some organic growers are using spary, it may be "Bacillus Thuringiensis (crystal toxins produced by a species of bacteria)... effectively of natural origin". I hope I've paraphrased the paper you quote from correctly.

Does this mean it's something like Derris, which whilst a pesticide for things like aphids, is produced from natural sources?

Of course, there are many naturally ocurring things that we wouldn't like to consume (eg. deadly nightshade, cyanide etc) but maybe that's broadening the debate too wide.

Personally I like to keep to a minimum anything I put on my plants or soil for produce that my family is then going to eat. I also have the luxury of gardening for pleasure, rather than on a commercial basis. Thus I've just ditched all my outdoor toms because of blight - luckily my spuds are fully grown & havn't yet had any blight.


Colin

[Cider Boys]

Hello Colin

What I’m attempting to clarify is to me a blatant hypocrisy.

Albeit a small percentage, the general public buy and support organic foods since they believe that it has less ‘harmful chemicals’ within the food and no harmful sprays applied in its cultivation.

The SA is mainly responsible for promoting these assumptions. All I am questioning is the truth behind these common acceptances. To me it has just become conventional wisdom without any questioning of the facts. Either the SA organic movement believe in the no chemical approach or they do not. I would respect the movement more if their approach was consistent. My example was potato growing - they can not control blight by organic methods so they should not promote their potatoes as organically grown, because clearly they are not organic by their own ideals. Further, I believe that their permitted use of copper to spray against blight is likely to affect the potato we eat! I have stopped using the old copper based sprays and use a modern chemical spray that remains on the leaf, unlike the copper based spray. My reasoning is based on the findings of eminent scientists not the SA which in my view is a self fulfilling pressure group to promote their members’ food.

Would Jo Public be so keen on eating organic potatoes, the ‘healthy’ food option, if they were aware of the scientific facts from a Royal Commission on Environmental Pollution, Pesticides study?

Barney

[Tigger]

As an Irish immigrant, I'm only too aware of the impact of blight, but I still grow my fruit and veg in order to eat produce that hasn't been sprayed. It's a bit like the survival of the fittest - if it doesn't make it, I don't eat it.

The only thing I will spray to control are the weeds on our gravelled lane. Nowhere near our food stuffs.

[alan refail]

It looks like the point is this: is this Forum and is KGM aimed at commercial producers or at home growers? I would have thought definitely the latter. If so, to promote commercial agricultural practices as suitable for the amateur/home grower is usually pointless and sometimes irresponsible.

My predictable swipe at Barney was made only in response to his equally predictable swipe at commercial organic growers. "Forget organic methods...." A case of the producer trying to teach the home gardener?

Alan

[richard p]

i think we all realise that commercial organic growers have to get a crop to make money, as such they have to in some circumstances comprimise their strict principles, to what degree some of them will do so is another debate, these economic forces do not apply to those of us growing for our own consumption, if the crop fails we either do without or trot to the shops. so we can afford to be idealistic on our own crops. what we buy when we get there (Organic, grown locally without sprays and fertilisers or conventionally mass produced) is for us to make an informed decision . we should all realise that commercial "Organic" may not be quite as unadulterated as first assumed. if you havent grown it yourself you can never be totally sure whats gone on. none of us can realistically completely eliminate chemicals from our diets, but we can significantly reduce the ammount we are consuming, too what degree depends on how idealistic we are prepared to be. eg if you want to eat peppers and tomatoes in february you have to buy them and accept what comes on them.

[Granny]

2 years ago we were entirely self sufficient in potatoes and also kept our neighbour fed all year as her got eelworm or something similar. Our following first earlies overlapped the last of the maincrop by about 2 weeks. Of course we didn't have blight then.

Dear OH, thank you for your kind comment of June 11. Would you like my postings in triplicate again?
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Granny