Be alert for potato and tomato blight

THOSE of you who read our Facebook page might have noticed that from May onwards we post regular blight alerts to warn plot holders who may need to protect their plants against one of the gardener’s biggest enemies.

Last year, however, many of our page’s followers were asking what a ‘Hutton blight alert’ was. So, with the summer finally upon us we asked St Julians Allotment plot holder WALLY KENDALL to tell us what blight is and how you can combat it.

Most dictionaries define blight as ‘a plant disease, typically one caused by fungi such as mildews, rusts, and smuts’.

If you’ve never lost a crop to this menace it’s difficult to describe how soul-destroying blight can be.

LateBlight03A windborne disease, Phytophthora infestans (Late Blight) will devastate potato and tomato crops from early June to late September

Initially it manifests itself as dark spots on the leaves of the plant before spreading rapidly to the tubers or fruit causing them to die.


There is no cure once blight has struck, therefore it is imperative that preventive measures are taken.

Most seed producers now offer F1 varieties – a hybrid of two plants that offer greater protection against diseases such as blight. Some potatoes (the Sarpo varieties) and tomatoes (Crimson Crush, Mountain Magic and Oh Happy Day)  have shown good blight resistance thus far.

Unfortunately the products that were used for many years – Bordeaux Mixture and Dithane 945 – are no longer available in the UK.

There is, however, a new product available from JBA Seed Potatoes. Called Blight Guard, it’s a 100% natural product, with no chemicals, which should be used every seven days to provide maximum protection.

If  your potatoes do succumb then remove all foliage completely and dispose of it. DON’T be tempted to compost it! This will only help to spread the disease.Potato-Blight-Effects

Leave the tubers in situ for three weeks before lifting, because the blight spores on the soil surface can remain active for some time.

Tomatoes are less easy to save, as the blight attacks both fruit and leaves at exactly the same time.

At the first sign of blight remove all of the fruits that are disease free. If they are already ripe then they are fine to eat. The green ones will also be fine to eat, but don’t be tempted to ripen them. Instead consume them immediately or use them to make chutney.

The Hutton Blight Alert

The Hutton Criteria simply replaces the old Smith Period alert – the methodology for predicting blight – which was phased out at the end of 2016.

Click here to find out more about the Hutton Criteria

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