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Potato Blight

How to Identify Potato Blight
The first signs of potato blight are dark brown markings on the edges of the potato plant leaves.

The next stage is that the leaves curl and the whole potato plant wilts and eventually falls over. This happens extremely quickly and the whole process can take only a matter of days.


Potato blight The picture on the left (click it to enlarge it) shows the first signs of potato blight. If you see this on a couple of your potato plants the only course of action is to cut the plant down to ground level immediately.

This will prevent the disease reaching the potato tubers under the ground.

Burn the foliage immediately because this is a highly infectious disease. The spores will live in the soil for a couple of years if they are not destroyed. The same fungus also causes Tomato Blight.

If the foliage is destroyed immediately Potato Blight is noticed, there is a very good chance that the potato tubers under ground will be unaffected. Growth of the potato tubers underground will be slow when the foliage has been destroyed but they will be edible and will store for some time in the ground. See the picture below to identify if the potato tubers have been affected.

Treatment of Potato Blight
Once you have it there is no treatment. To help avoid potato blight there are two main courses of action:

1. Destroy all infected plants by burning them. Do not plant potatoes (or tomatoes) on the same patch of land without leaving an interval of three years.

2. Spray potato and tomato plants with Bordeaux Mixture (available at most garden centres) in May and June to help prevent infection.

As far as we are aware, eating potatoes infected with potato blight will not cause serious medical problems.

However the picture on the right shows the effects on the tuber if the disease is left to take its natural course. Its not as pretty sight I am sure you will agree,

Crop Rotation
The fungus which causes potato blight goes under the name of Phytophthora infestans. It is spread by either wind or rain in temperatures above 10oC (50oF)

Avoid it occurring in subsequent years by good crop rotation and burning all infected plants as soon as the disease is noticed.

The Potato Council have distributed two fact sheets on Potato Blight which can be found here.

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Name: Jill
E-mail: jillhodgson19@yahoo.co.uk
Date posted: September 18, 2011 - 09:07 am
Message: Could you explain why my potatoes just turn all mushy why I cook them they havent grown very big even though they have been in since the end of April

Name: andrew raine
E-mail: andrew.raine@hotmail.com
Date posted: June 23, 2011 - 05:44 am
Message: can i pick my potato crop now it seems a long time in flowering although i have plenty leaves and they are earlys

Name: steve jones
E-mail: sueelgey@hotmail.co.uk
Date posted: August 21, 2010 - 06:47 am
Message: Hi i have just dug up my salad potatoes and have noticed small white specks on them, they do rub off and the potato seems healthy, is this ok

Name: Vicky McIntosh
E-mail: vmcintosh@talktalk.net
Date posted: August 20, 2010 - 02:12 pm
Message: My potatoes have grown very, very high leaves.
They were planted at the end of May and still flowering & growning bigger every week. Any advice?

Name: mandy
E-mail: Private
Date posted: August 01, 2010 - 02:32 pm
Message: can you please tell me why my home grown potatoes split when i cook them.look forward to hearing from you.