Potatoes - Blight, disorders and mineral deficiencies.

[ideasguy]

Is anyone growing potatoes this year?

For the first time in years, Ive planted a few drills of a variety called Kerrs Pinks.
Last time, I lost my crop due to blight.

Ive invested in a backsprayer and am spraying with Dithane Dry Flowable:-
http://www.dowagro.com/ie/products/prod/dithanent.htm

Ive been using this site for info on Blight warnings:
http://www.dardni.gov.uk/index/farming/crops-and-horticulture/potatoes/pot-management/blightnet.htm
The closest station to me is Newforge.
The information has a lag of 3 days

I haven't been satisfied so far with information Ive found about protecting crops against blight on the internet.
My problem (and the reason for this topic) is what to do when a spray program coincides with a really wet day, or worse still a really wet period.

My account, for anyone interested!
I have sprayed every 7 days as the plants grew and I was naturally worried about blight.
I sprayed on the Thursday before going off on holidays.
Back home, weather still fine, doing catch up in the garden I decided to go the full 14 days as instructed on the product info (above).
It rained heavily on the 14th day (Thursday). (Sods law?)
I sprayed on Friday.
On Monday, I spotted "something" on the uppermost leaves of some plants.
It could be blight but from my research on the net it could also be a mineral deficiency.
If its a Magnesium deficiency (possible) I may be able to take some action.

Problem is (again the reason for this topic creation) the photos of problems seen on potato leaves on the sites Ive visited on the internet are rather poor.
Very difficult to make a positive ID from anything Ive seen to date.

Heres a website offering advice (open the pdf):
http://www.potato.org.uk/publications/managing-risk-late-blight

Discussions on the forums Ive visited pose more questions than answers.
Worse still, people who have posted photos asking for advice don't follow up the topic to a conclusion to say what the outcome was - e.g. did the plants produce a crop or did the "problem" kill off the plants?

Ive been worried about the heavy rain this week. Will it wash the spray off?
If the rain has washed the spray off they are completely unprotected and from bitter experience, this is the most dangerous period (humid) in a warm and wet. Should I spray again?
I rang a farmer friend on Monday evening (after a downpour) for advice.

14 days between sprays (Humph!). More like maximum every 7 days when high risk.
What do farmers do when its a wet week?
He knows at least one grower who sprays every 3 days.

It was a dry start to the day so I sprayed again next morning (and applied a heavier application than usual) even though heavy rain was forecast for the afternoon.
It came with thunder and lightening and it rained even heavier this afternoon and evening.
I checked the foliage this morning and could see traces of the spray in place

Can we do better on this forum?
I'll take a photo of my potato leaves tomorrow and post here.
We have a number of veggy growers in our membership, so hopefully we can pool some advice and decent photos to help each other (and any guests who visit our forum).

Tonight, Ive signed up to blightwatch:
http://blight.potato.org.uk/signup.html

Other websites Ive found of interest are:
http://chat.allotment.org/index.php?PHPSESSID=90ea601b9fc37a619e8cb7a82beb59c2&topic=56717.0

Note (quite incidental): Ive also sprayed my apple and pear trees a few times with Dithane Dry Flowable. I had a serious attack of Apple Scab on my Bramleys 2 years ago. So far, my Bramleys are holding their leaves and the fruit is very green (no blotches), healthy and growing very well.

[NightHawk]

That's a very detailed and informative post George, but sadly I'm not able to contribute anything of value in this case 

We've never grown potatoes.

Hopefully, there will be other potato grower members out there who can help though.

[Palustris]

And you eat this stuff after spraying with  those chemicals?

[ideasguy]

Yes, that's the general plan Eric 
Not much choice - That's what was available and recommended in the Farmers store where I bought the stuff.

I had most of that typed up last night, Laurie. I then opened another website to get a link to add to the article (thought I HAD clicked a new tab) and the site replaced the message I was typing Grrrrr!!
Had to start it all over again.

[ideasguy]

Heres the photos, taken this morning.
Three photos of the TOP side of the leaves.
I'll follow up with photos of the underside later (when/if it stops raining ).

[roiphil]

George bad news on your potatoes, i dont grow potatoes myself but i was researching into a disease on xmas trees and it was recommeded bordeaux mixture looking further into bordeaux mixture i am sure i read it can be used for potatoe blight, (by now my brain is full of what disease it could be what chemicals sorting out american stuff etc etc) could be worth taking a further research look into that stuff it may help you

Phil

[ideasguy]

Thanks for that info Phil.
I did a search on bordeaux mixture for potatoes and found this
http://apps.rhs.org.uk/advicesearch/profile.aspx?pid=217

In particular, read the section on Chemical control.
I think Eric would be happier if I were to use your bordeaux mixture as its a protectant fungicide containing copper.

The site above had a link to this:-
http://apps.rhs.org.uk/advicesearch/profile.aspx?PID=456

Good reliable info from the RHS

[roiphil]

glad it helped 

[Eric Hardy]

Just tuned in George. Not good news at all  Like Laurie. we are not potato growers. The nearest thing we grow are tomatoes where I believe the same rules apply on the rain front. Just had a look at them and (fingers crossed)  they seem OK. i don't know whether preventative spraying is necessary or not. Our packet of dithane says "spray on the first signs of blight".

We had blight in the greenhouse last year but even Monty Don had blight on his greenhouse tomatoes then.

Good luck with your spraying.

ERicH

[ideasguy]

So far (touch wood) out tomatoes are fine. In fact we have a bumper crop and have been eating them for a few weeks now.
Ive read that they are "safer" in the greenhouse as the airborne spores have to find a way to get to them. I don't have any growing outdoors.

From the weather forecasts, I can see you folk in south and east of England are having blazing sunshine. We are sitting under those large clouds you see over Ireland. It rained all afternoon and evening yesterday and also this morning.
Its cleared up. Sun is out as I write (over coffee) and I've got some much needed weeding done.
Hey ho, hey ho...

[NightHawk]

Yes George, the south of England is indeed getting great weather again today.

Sunshine, blue skies, a slight breeze, but very hot though.

Typical for me though - I'm getting the start of another darn cold.  Tickly throat yesterday, and same today 

[Eric Hardy]

Sunny and v. warm here too eased a little bit by a gentle southerly breeze. I have just put the car in the garage and the thermometer said 32 degrees. Actually had to do a little bit of watering on those plants that don't like to be dry, such as the bamboo which we have in a large pot.

Eric H

[Palustris]

Copper sulphate is no longer sold as a garden fungicide, but I am told you can get it from Wine Making shops.
We do not actually spray with anything. We only grow earlies and they rarely get it. One thing you can do is to remove the top growth once Blight appears. It reduces the crop but at least you get one and the potatoes are clean.
Helps with Toms if you remove the lower leaves as the Blight spores bounce up from the soil on to them

[ideasguy]

Thanks for that info and advice Eric.
This site may explain why Copper Sulphate is no longer sold:-
http://www.gardenersworld.com/blogs/allotments/potato-blight-and-bordeaux-mixture/2965.html

...he seemed alarmed that I intended to use Bordeaux Mixture. He classes this as far more poisonous than the conventional fungicide Dithane 945, which breaks down in the soil after a few days. Similarly Iain Barbour of JBA seed potatoes in Scotland also recommends Dithane 945 for the same reason. Copper sulphate is a poisonous substance which neither bees nor worms care for and can take a long time to break down in the soil.

Its an OLD document. The more I read, the more evidence I find of potato Blight (Phytophthora infestans) developing resistance to chemical control and also mutating to be able to attack so called "blight resistant potatoes".
Its a big challenge, so any recommendations then may not apply now!

Edited later - this site recommends it AND mentions the dangers:
http://howtogarden.ie/prevention-better-than-cure-with-copper-sulphate/

Edited later again. This site supports Phils recommendation earlier - use Bordeaux mixture:-
http://greensideup.ie/8-tips-for-managing-potato-blight/

If you can manage to get your "earlies" sown early and ready for harvest mid July, I agree with you that its the easiest way to grow potatoes. That way, they are on the table before the blight usually starts!

Heres a few photos of the underside of the leaves on my crop:-

[trishs]

Haven't grown potatoes for ages, not enough room to spare.  Impressed you've been eating your tomatoes for weeks already!  Lucky you!  I thought I'd made a good early start this year, but even with this recent good weather we're still a long way off getting anything edible from our various plants in greenhouses and outdoors.

[Palustris]

We dug up our potatoes today. Not a very good haul and they were a long way down in the soil. Presumably the roots had gone looking for moisture. Despite the recent rain our soil is still very dry and has been for months. Still there will be enough to last us until well into the New year. No sign of blight on them and only a couple damaged by keel slugs this year.

[ideasguy]

We used to be able to dig as we needed them Eric.
I presume you have dug them, all up. How long do they keep? As I understand it, earlies don't store as well as late varieties.
This topic has provoked even more research. I have to confess I don't know much about the varieties of slugs and snails - they are all on my hit list. I went surfing on keel slugs and found this:
http://www.slugoff.co.uk/slug-facts/bad-slugs

[Palustris]

We find the Earlies and the Second Earlies keep as long as we need them too, ie until we get the first crop from in the Tunnel. They are not supposed to store, but they always have for us. We do not leave them in the ground as if there is any Blight then it gets the tubers. Also we use the land for other later crops, so once it has been raked over, she will sow carrots, beetroot, Mooli and Black Spanish Radishes etc.

[ideasguy]

The good news is - whatever it was that was on my potato leaves, it wasn't blight - phew!

I dug my first stalk yesterday and what a relief to see they look really good:-


The stalks are still green so I'll dig as required for a while yet.

[Eric Hardy]

We don't grow potatoes. George. Seeing your crop makes me quite envious 

Eric H

[ideasguy]

They are hard work Eric. Spraying every 10 to 14 days is time consuming.
Add on the stress worrying about blight and it becomes a major concern.

I reckon my neighbour on the other side of the road lost his crop in a large garden to blight.
Seeing it so close was VERY worrying. Worse still, the prevailing wind was coming directly from their direction
There were also quite a few Smith Periods recorded and I received blight warnings by email from the Blightwatch site.

I think its best to leave it to the professional growers. I take my hat off to them.
Its bad enough having a few drills to worry about. Its a different scene when its your source of income.
They deserve medals. Think of them next time you have a nice dinner

Seeing those lovely spuds has made it all worthwhile (I think!?  )

[Eric Hardy]

Sounds like too much hard work, George  . You have successfully put me off trying  But you do have some beautiful fresh spuds to eat straight from the garden - which is a good reward for all that effort.

Eric H

[NightHawk]

Very lucky indeed with your crop there George - it could have been a disaster.

Like Eric, we don't grow potatoes either, never have done.

I also agree that the growing regime and threat of blight sounds far too stressful to even attempt growing them.

Hats off to the expert growers 

(P.S. George, it looks like you 'assaulted' one of your humble spuds with your spade.  The one at the top of the pile in your photo has a nasty gash in it - poor thing  )

[ideasguy]

Well spotted Laurie! Yes, I dug them very carefully with a grape, but I spiked that one I started in the middle of a row on a plant that looked like it was beginning to die off (in its natural cycle).
Its easier to start at the end!
It would have been a crime if it had been one of the bigger ones

[Palustris]

The professional growers do not get Blight to the same extent as gardeners, but then they spray, spray, spray and spray again. Not sure what they use but it obviously works. Mind I prefer not to eat chemically impregnated food.
They also spray something on the haulms to kill them off before lifting the crop. It used to be Sulphuric acid, but not sure if they use that any more. That not only killed the tops it also killed off any blight spores for future seasons.
Good crop George.