Potato and tomato blight is an airborne virus caused by a fungus-like organism, which spreads rapidly in the foliage and tubers or fruit of potatoes and tomatoes in wet and humid conditions, causing collapse and decay.
It is a serious disease for potatoes and outdoor tomatoes, but not as common on tomatoes are grown in greenhouses and polytunnels.
How to Spot Blight
The earliest symptoms of blight on potatoes is a rapidly spreading brown, watery rot of the leaves. These soon collapse and can also affect the stems. If it is allowed to spread, blight will eventually reach the tubers and then spread to any tomato crops growing nearby.
The symptoms on tomatoes are similar to those on potatoes. Brown patches may appear on green fruit, while more mature fruits will decay rapidly. Remove any blackened or discoloured leaves. Get them out of the way before the problem gets the chance to spread any further.
Can You Stop It?
If blight arrives, all you can do is try to slow it down. Remove any affected leaves and fruit immediately, then spray everything with a solution of bicarbonate (baking soda), 10g per litre. Add a couple of drops of a plant-based detergent to help the solution stick to the leaves.
The Blightwatch website is FREE to sign up for Smith Period warnings that are now calculated based on data from the entire UK at postcode level. Once you register you can request warnings, either by email or text to your mobile phone of Smith Periods in up to 10 postcodes near your garden or allotment.
For more monthly growing tips and advice please visit First Tunnels Growing Guide
Originally posted 2011-07-19 08:54:18.