Tomato Troubles & Diseases

by John Harrison

You'll find a host of potential problems with tomatoes listed in the gardening books but in the real garden it does not seem to be so complicated.

Greenhouse Tomatoes
Blossom End Rot in Tomatoes


Tomato Blight

This is really potato blight, don’t forget tomatoes are the same family as potatoes, so you can get blight.

My experience with blight is that there is little you can do if they get it and just to accept defeat. You can prevent blight by practising good hygiene when it is about and using clean mains water rather than water from an outside butt.

There are fungicidal sprays you can use that will help if used at the very first sign of blight.

Tomatoes that are ripe on the plant can be used but the rest will probably rot without treatment

Virus Infection

Tomatoes can get virus infections and these too can be fatal. Symptoms are usually yellowing or mottling of the leaves and reduced yield.

In this case, I cut off badly affected leaves and hope the gods will give me some fruit. Sometimes it doesn't make too much difference and you can basically ignore the infection.

No Smoking

Smokers should keep in mind that tomatoes can catch a mosaic virus carried in tobacco and so you should never handle the plants whilst or just after smoking.

Washing your hands after a cigarette before handling tomato plants is a good idea. In commercial greenhouses they use anti-septic sprays for hands just like hospitals (only they really insist the spray is used, unlike the hospitals)

Magnesium Deficiency in Tomatoes

This is a problem where the plant looks like it has a virus with yellowing leaves but it is caused by lack of magnesium. It is easily treated by spraying with Epsom Salts. Dissolve ½ oz in a pint of water (20g/litre) and spray each day for a week.

Even if I am fairly sure the plant has a virus, I give an Epsom salt spray – it can not do any harm, is perfectly safe and cheap. If it is deficiency the plant will benefit and even if a virus, it may help if deficiency is present.

Tomato Blossom End Rot

This is where a brown patch is seen on the base of the fruit. It is caused by the plant drying out with irregular watering so the cure is to ensure your plants never dry out. At the same time, do not allow them to get too waterlogged or you will drown them. Regular watering is critical to success with tomatoes.

Tomatoes Splitting & Unripe Patches

This is caused by allowing the plants to dry out and then watering heavily. There is no cure, just ensure you water regularly - little and often is by far the best with tomatoes.

Tomato Pests

Tomatoes can suffer from aphids, green fly, white fly and slugs. I hang yellow sticky cards in the greenhouse to control white fly and slug controls for the outside ones. Apart from slugs eating the fruit, tomatoes do not seem too bothered by pests. It may be that I have been lucky.

Soil Sickness

Like most plants, it is not a good idea to grow the same thing in the same spot year after year.

If you grow in a greenhouse with soil borders, grow the tomatoes in the soil by all means but dig this out and replace with fresh soil each year.

With outdoor tomatoes rotate them. They are the same family as potatoes but do not grow next to potatoes because they are susceptible to potato blight. If they are far away from the potatoes they may well escape it. You can also try shielding them with clear plastic walls or even build a large cloche as the season ends.

Tomato Greenback

The top of tomato around the stalk remains hard and remains green, refusing to colour. The main cause is a lack of potash but it's more common in hot, sunny years so using shading in the greenhouse will help. Many varieties of tomato do not suffer from it.

Tomato Leaf Curl

You will often see curled up leaves on tomatoes – this is not a problem! It just happens and doesn’t seem to harm the plants, fruits or flavour.

Further Information: Tomato Growing Guides



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