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Potato and tomato blight: what is it and what can I do about it?

Heard of blight but not sure how to spot it? This informative post from Mark, our membership secretary, should make for useful reading.


I had blight in my main-crop potatoes last year and lost quite a few to the disease, so I’ve been keeping a close eye on my plants this year. Potato and tomato blight, properly called late blight, is a fungal disease of the foliage and fruit or tubers of tomatoes and potatoes. It causes black spots on the foliage and rotting of the tubers and is most common in wet weather. Unfortunately, there’s not a lot us gardeners can do once our crops are affected: there aren’t any fungicides available against blight. The best approach is to keep a look out for the first signs, and act quickly, as well as gardening hygienically!

Some top tips:


Tip 1: Look out for the first signs.

I had noticed brown spots on the leaves of my first-early potatoes last week. As you can see in the photographs the spots are on both sides of the leaves.


Tip 2: Harvest early if you spot the signs.

If you catch it early enough the potatoes can be harvested. I took mine out on Monday 22nd June, less than 12 weeks after planting. The tubers were smaller than I would expect but there was no damage to them.


Tip 3: Dispose of affected plants carefully.

As blight is a fungal disease, it is spread by microscopic spores. These can be spread in water, soil or by the wind, so it is beneficial to you (and other plot-holders) to minimise the chances of the spores spreading. Avoid washing your crop on the site, take the tubers home to wash and dispose of the water there. Avoid composting the haulms (stems and leaves) or saving them for the bonfire. The RHS recommends you take any plant material off the plot quickly.


Tip 4: Avoid growing potatoes and tomatoes in the same place for 3 years.

Crop rotation is useful for preventing many pests and diseases, potato and tomato blight included.


Good luck avoiding blight and enjoying bumper potato and tomato harvests!


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