Tomato blight

How to identify tomato blight

Spread by airborne spores that can be carried over 30 miles on the wind, tomato blight is most prevalent when conditions are warm and wet. Outdoor tomatoes are more susceptible to blight than those growing in a greenhouse.

When affected by blight, ripening tomatoes develop brown sunken spots, which spread to the leaves and stems.

In this video, Monty Don explains what to do if blight affects your tomatoes, and explains whether you can still eat the tomatoes growing on blight-infected plants:

How to prevent tomato blight

Keep tomatoes dry

Grow tomatoes in a greenhouse or polytunnel if possible, as this will keep the leaves dry and help fruits ripen sooner than those grown outside.

Never plant tomatoes in soil or compost that has previously contained diseased plants.

Support tomato plants with a stake, including bush varieties, to keep their leaves off the soil.

If growing tomatoes outside and blight hits, try placing an umbrella of polythene or a plastic roof over tomatoes to keep the rain off them. This will stop rain splashing onto the leaves and reduce the likelihood of infection.

When watering tomatoes, water in the morning, so the plants don't sit damp all night. Take care to water only the soil or compost, keeping the leaves dry. Remember, tomatoes taste better if the plants aren't overwatered.

Feed tomatoes with fertilisers that are high in potassium, such as dedicated tomato feeds. Never feed tomatoes with a high-nitrogen fertiliser as this boosts leaf production, making blight more likely.

Provide good ventilation

Pick a sunny, well-ventilated spot for growing tomatoes outdoors. Leave enough space between plants for air to circulate – don't be tempted to plant closer than the seed pack recommends.

Remove lower leaves, and some higher up, to increase air circulation. Vigorous bush varieties produce too many leaves and benefit from drastic pruning to thin the foliage and encourage good ventilation.

Stop greenhouses or polytunnels becoming too humid. Keep them well-ventilated, mop up water and, as the evenings turn cooler, use a heater to reduce condensation.

Avoid planting tomatoes near potatoes

Don't plant tomatoes near potato crops, as these are also susceptible to blight and their proximity will make it easier for the blight to spread between crops.

Check plants regularly for blight, from summer onwards, and dispose safely of badly diseased plants.

When the weather conditions are optimum for blight, remember to check your tomatoes and potatoes more frequently.

Grow early tomatoes

Cherry tomatoes tend to be less likely to catch blight than beefsteaks, because they ripen earlier and are often harvested before blight hits.

Practice good hygiene

Once blight hits, destroy blighted foliage to reduce chances of further infection. Burn the waste, bury it underground in a deep hole or add the material to your green bin. New blight strains in the UK may be able to produce resting spores which remain on foliage overwinter and could reinfect plants the following year. Don’t leave potato tubers in the ground at harvest as they, too, could harbour blight.

Blight resistant tomatoes to grow

Some tomatoes have been bred with a degree of blight tolerance – they may still catch the disease but are able to survive and yield some healthy fruit. Here, Monty Don picks the fruit of blight-resistant tomato variety 'Losetto':

We've picked our favourite blight-resistant tomatoes to grow, below.

Tomato 'Berry'

This unusual cordon tomato produces strawberry-shaped, cherry tomatoes that have a super-sweet flavour. It’s early to ripen, and shows some resistance to blight.

• Buy tomato 'Berry' from Marshalls

Tomato 'Fandango'

A blight-tolerant cordon tomato, reliable, and resistant to fusarium and verticillium wilt. It produces a heavy crop of medium-sized, deep red fruit with an excellent flavour.

• Buy tomato 'Fandango' from Crocus

Tomato 'Fantasio' F1

A superbly flavoured cordon tomato, bearing a prolific crop of medium-sized fruit. Blight tolerant and resistant to fusarium and verticillium wilt, it's best grown under glass.

• Buy tomato 'Fantasio' from Suttons

Tomato 'Ferline' F1

This cordon variety has some blight tolerance, and resistance to fusarium and verticillium wilt. 'Ferline' bears heavy crops of tasty, medium-sized fruit.

• Buy tomato 'Ferline' from Thompson & Morgan

Tomato 'Latah'

Bush variety 'Latah' produces very early, large, cherry tomatoes, with excellent flavour. Its sprawling habit and well-spaced leaves help fruits ripen before blight strikes.

Tomato 'Legend'

Bush variety 'Legend' holds the RHS Award of Garden Merit and has some blight tolerance. A beefsteak variety with heavy crops of large, it produces almost seedless fruit with superb flavour.

• Buy tomato 'Legend' from Thompson & Morgan

Tomato 'Lizzano' F1

A vigorous variety with lots of sweet, round cherry fruits and a trailing habit, 'Lizzano' is perfect for pots and hanging baskets. It also has good blight tolerance.

• Buy tomato 'Lizzano' from Suttons

Tomato 'Losetto' F1

This very blight-tolerant variety produces masses of bright red, sweet cherry tomatoes. 'Losetto' is ideal for growing in pots.

• Buy tomato 'Losetto' from Thompson & Morgan

Tomato 'Red Alert'

Bush tomato 'Red Alert' bears a lot of small, sweet, cherry tomatoes. Its sparse leaves reduce humidity and fruits ripen very early, so are often harvested before blight strikes.

• Buy tomato 'Red Alert' from Suttons