Friday, 15 July 2016

Combating Potato Blight

There is no denying the Spring of 2016 has been both cool and wet which has meant I have been really late getting things going in the garden.  That said, so long as we get a good Autumn (fingers crossed) this should not be a problem and plants will simply be ready a bit later in the year - there is one notable exception to this though and that is my potatoes.   My potatoes went in late and now have succumbed early to the dreaded disease that is blight thus giving them no time to grow tubers of a decent size. 

So what is blight?  It is a fungal airborne disease that affects potatoes, initially killing the foliage and then passing down underground and affecting the potatoes which can rot to a black slime when stored.  If you  know your (Irish) history you will have heard of blight as it is the potato disease that caused the Great Potato Famine in the mid 1800's when it decimated Irish potato crops leading to an estimated million deaths from starvation and a further million peasants leaving Ireland to try and find a new and better life in America.

Healthy potato plants in the polytunnel

Black marks on potato leaves - the first sign of blight

Blight causing the potato leaves to blacken and shrivel all over
People have asked me before why I bother growing potatoes when blight all too often attacks them and they are relatively cheap to buy.  The reason is simple - taste.  There is just nothing better that a freshly dug new potato eaten cooked and eaten within moments of digging.  Also I can grow several different varieties which I like for different ways of cooking:  you cannot beat a King Edward for roasting nor a Kestrel for boiling, in my opinion.

Combating Potato Blight

Unlike for the Irish peasants who could simply stand by and watch their food source rot before their eyes, there  are ways to combat blight, although not all are ideal in my eyes.

1.  Plant blight resistant varieties
The trouble with this is their yield is often less and their taste/cooking quality nowhere near as good as the varieties I like to grow.

2.  Spray against blight
The use of  Bordeaux Mixture is accepted in organic cultivation but this is still a really nasty chemical which can also kill earthworms and bees.

3.  Cut off the affected leaves (haulms)
As soon as the disease is seen but off ALL the foliage and dig the tubers a few weeks later (in slug free area you can even leave them in th eground to the autumn).  By doing this as soon as blight is seen you can usually save the potatoes and they should store safely.  You can find more details in this blog post here.  This method however does rely on getting the potatoes in early so they have enough time to grow big enough to store.  This has NOT bee the case this year.

4.  Plant them early
I was talking on Twitter with Nicky Kyle who gardens organically in Ireland and she starts her potatoes in pots in the polytunnel early in the year and then transplants them outside after the risk of frost has past.  She concedes it is extra work but it does mean the tubers have time to grow even if blight hits early in the year.  I really do like the sound of this idea although I will need to be extra vigilant for frost which will occur later here in Normandy.

5.  Plant them in the polytunnel
I have always grown a few potatoes in the polytunnel borders for extra early crops and these are more protected.  This year, having been away a lot I had not got round to harvesting them so I have decided to leave them to grew on as bid as possible.  Yes, they do take space that could be used for other crops such as tomatoes but I do think I can sacrifice this if the result is some decent sized spuds.

6.  Plant some tubers late in the polytunnel
Whilst having a clear out I found a few tubers I had not planted in the Spring and have planted them in the polytunnel.  My trusty polytunnel book says this should give new potatoes at Christmas time so we shall have to wait as see.  It is certainly worth a try as I had a bit of spare space having decided to grow less aubergines this year and cleared some cape gooseberries that no-one really liked (they were very small and sour) ... and I have horticultural fleece ready to try and protect them should we get early frost.  Last year (2015) we had a similar cold, wet spring and then a fabulous autumn with no frosts until the New Year and really warm temperatures right through to Christmas.

My plan therefore is to make much greater use of the polytunnel when growing potatoes and not resort to inferior blight resistant varieties or chemicals.  It will mean more work and I will probably grow fewer plants but if the end result is I get bigger potatoes that I can store I reckon it will be worth the extra work.  I will  I'll let you know how I get in.  In the meantime do you have any further tips for combating potato blight?

Linking this post up with How Does Your Garden Grow over at Annie's Fable and Folk blog.


  1. Really useful post Rosie. Our veggies have been slower to start this year too so I'm hoping the Indian Summer predictions are true.

  2. Great post Rosie. I agree it's worth growing potatoes despite the blight risk. Both the texture and taste in homegrown are so much different to supermarket potatoes. Last year we had blight but managed to catch it in time; cutting off the foliage prevented it from spreading into the potatoes. The potatoes we've grown this year have made wonderful chips!