I was talking with a friend the other day about the merits of blue stone (copper sulphate) and the problems. He suggested that Diathane http://www.dowagro.com/ie/products/prod/dithane945.htm was less damaging to soil life than the blue stone. This is not the first time I've heard this
The last few years I have had poor results from the supposedly blight resistant varieties (except Sarpo Mira, but the wife doesn't like them) and lost the tops to blight by mid july last year, so I have decided to grow conventional varieties and spray
What do you spray?
What are your thoughts on bluestone or Diathane?
Are there any other options?
ina wrote: die dümmsten Bauern haben die dicksten Kartoffeln
I use copper sulphate mixed with slacked lime (aka Bordeaux mixture) for all my blight requirements. I've always understood this to be relatively environmentally benign - copper is an important trace element for animals and plants and is really dangerous only to fungi and algae. In France at least, Bordeaux mix is allowed in organic farming, subject to certain limits on application.
Diathane, on the other hand, and speaking as a chemist, I would not use. Diathane's active ingredient is something called Mancozeb, which belongs to a class of chemicals called dithiocarbamates. One of the breakdown products of Mancozeb called ethylenethiourea (ETU) is known to cause thyroid problems and cancer in test animals and is persistent in the soil for several weeks after Mancozeb application.
Now, there are - as far as I know - no studies linking the kind of quantities of ETU likely to be found on fruit and veg treated with Mancozeb (though the EU limit for Mancozeb residues on potatoes is a fairly stiff 0.3ppm) but I work on the basis of why chance it? The incidence of cancer, allergies and chronic illnesses seems to be on the rise and something must be behind it.
It is a really hard call all this spraying with stuff. I used a home made burgundy spray a few years ago, and I was not really that happy with doing it, I hate spraying with anything. So I don't, ever spray any pesticide. There can be a problem with a build up of copper in soil, but I don't think in a normal garden this would probably be an issue, if pigs are fed with food where copper is a growth promoter, if their dung is regularly spread in the same place copper can build up, land tested on a pig farm where I used to live had very high levels.
I prefer to use my own home spun and wibbly wobbly methods. I used no dig raised beds, I do no dig spuds, all spuds are planted out in February as soon as I get a dryish day, compost goes down, spuds go just under the compost, everthing is covered in newspaper or feed sacks and then it is mulched with straw, then as they come up they get 'earthed up' with grass mowings, then I harvest all my spuds around the second week of August, even if they do get blight in late July, I can keep taking off the tops until it gets too bad then just swipe off the haulms and leave them for a week or so before getting them up. I foliar feed them with some seaweed about three times, can't do them any harm, I have this theory that the grass mowings and straw has some bearing, last year, everyone had blight in June and it was a good 6 weeks before mine got it, but not badly. Does the thick mulch help by keeping mould spores off the soil so it isn't splashed up by the rain, I don't know? just my theory, I do the same in the tunnel with tomatoes and they did not get any blight at all last year. I don't worry about sowing so early, they make roots under the ground before the tops, I can always fleece any growth if a frost is threatening, volunteer spuds come up and they have been in the soil for ages without any ill effects, so I just ignore people that say it is too early to plant them. My yields were down a bit last year, but not that much, we only ran out at the end of February, so not too awful.
Had a wee touch of blight on my first earlies last year but this was end July and I cut the stalks down, left them in the ground and harvested them over the next few weeks. They were fine. This year though I've planted some main croppers as well and had read that a horsetail tea works well against blight. Has anybody tried this successfully?
I was advised over the weekend that nettle tea is quite useful too, particularly when the blight affects tomatoes. I'm taking a year off growing potatoes this year to give the soil a break. That way I'll be able to plant in soil that hasn't seen a spud for three years at least. I'm hoping that this might help.
garye wrote:... read that a horsetail tea works well against blight. Has anybody tried this successfully?
Hi garye
I have heard this too, and also that it must be re applied after rain
Aye, apply when it's dry and then re-apply after rain - if it works then at least it would stop me being so pissed off at having the bloody stuff in my garden in the first place!
Found a couple of recipes, for every 2 ozs horsetail, add two pints of boiling water and steep over night, use undiluted. Or 1kg horsetail to 20 litres of water, steep for 4 weeks stirring daily (sounds smelly). I have been adding horsetail tops to my dry method comfrey and nettle liquid feed, wonder if you could just make a horsetail concentrate, will give it a go, far less smelly and could be bottled for later use.
Odsox wrote:I can't see that it will be an issue if the year so far is anything to go by.
You need 48 hours of temperatures ABOVE 10°C and that aint happened yet.
Well, so much for that
My spuds are now a pleasant shade of blue
ina wrote: die dümmsten Bauern haben die dicksten Kartoffeln
