Fruit and Vegetable Gardening > General discussion

Potatoes - Blight, disorders and mineral deficiencies.

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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.

--- Quote ---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.

--- End quote ---
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 ::)).

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