Tomato Blight Treatment

Before beginning a tomato blight treatment, it is best to make sure that your plants have a fungal infection, so here’s the information you need below.

Tomato blight (also known as potato blight) is a fungal disease which is caused by wet, damp conditions and mainly affects tomato plants growing outdoors.

However, greenhouses that are poorly aerated can also be a cause of blight because of high humidity and condensation.

If it has been wet in your area for a prolonged period, and you are growing tomatoes outside, it is possible that your plants have blight.

There are two types of blight
Early Blight, (below) shows itself as dark round spots surrounded by concentric rings that fade to yellow. Wet leaves combined with cold temperatures in the Spring will leave a plant susceptible to early blight.

Early Tomato Blight

Late Blight (see below) is the most common and devastating type.

Late Tomato Blight

It starts as brown patches on the edges of leaves that spread to darkened areas on the stem, then eventually the fungus will take over the entire plant – fruit too as in the photo above.

The combination of wet leaves and high humidity over a prolonged period is almost curtain to cause tomato blight. As a fungal infection, it can easily spread from plant to plant and on fingers too, so it’s best not to touch plant leaves and run the risk of contaminating healthy plants.

It is common to have a touch of fungal infection on one or two lower leaves when growing outdoors if you live in an area that gets a lot of rain. Remove the infected leaves and leaf branches, and keep the base of plants free from decaying leaves. Good air circulation at soil level helps keep plants healthy.

Tomato Blight Treatment
However, if blight has affected a number of leaves it is time to spray with Dithane 945 or apply Bordeaux Mixture. This may stop the disease spreading, and more importantly infecting other plants, but there is no cure for blight, it is only possible to stop it getting worse.

How to prevent tomato blight
If growing outside provide some kind of shelter for your plants if possible. Wet leaves are ok for a few hours, but over-night in damp conditions followed by another wet day will lower the plants defenses.

Ferline and Legend are supposed to be blight tolerant – that is they have a greater defense against blight than other varieties. The seasons 2008 to 2010 where very wet in my area and every variety that I grew, including Ferline, contracted blight.

More suggestions to follow

Keep tomato leaves dry – provide some shelter from the rain if possible.
Water in the morning to that plants are not stood in excess water overnight.
Remove some of the lower leaves (by pulling off – not cutting) if they show signs of infection.
Don’t touch leaves of plants and spread the disease on fingers.

If all else fails the last resort to save your plants is spraying with a protective fungicide. This is available from garden centres and in the UK is called Dithane 945.

Each country has its own brand of fungicide available to gardeners so you just need to do a search for “fungicide treatment for tomato blight” and you should find a suitable product.

I sometimes hear people say things like: “a drop of rain will do them good” and “when you water, water the leaves too” my advice is to keep those leaves dry. The only time I will allow my leaves to get wet is when I foliar feed which I do on a dry day.

Rain water is good for tomato plants because it is usually slightly acid, which is how tomato plants like their water and soil!

If you need to spray your plants with a tomato blight treatment, use gloves and spray on a day when there is no wind otherwise you may get the spray blown back in your face – it’s strong stuff!

Also, cover tomato flowers with a tissue to stop the blight treatment from being applied to them.