Blight on Tomato Plants?

Even if you’re growing tomatoes in a greenhouse or polytunnel you may find them struggling with blight this season. It has been so cool this August, and without the sunshine and dry air, it’s easy for blight to take hold.

What is blight?

Blight is a fungal-like disease that affects potatoes and tomatoes. Once infected, the plant foliage turns brown, and then the infection seeps into stem and fruits as well. It is most common during cool, damp weather.

How do I recognise it in tomatoes?

Look for brown patches on the leaves and stem as a first symptom. If fruits are forming already, you may see some small brown circular patches on the young, unripened fruit – these will grow in time and the entire fruit will begin to rot.


What can I do about it? 

If you see signs of blight on leaves, cut the affected leaves off as soon as you can to prevent spread, and destroy them. With luck, you may have caught it early enough and the fruits will come through ok.

If you see signs on the stems, or on fruits, then it is likely that all subsequent fruits from the plant will be infected. In this case, we’d prune off the unripened, unaffected fruits and try to ripen them on a windowsill in case they come through ok. Meanwhile, pull up the plants and destroy.

What about next year?

You can try again next season. However, practice crop rotation if growing outside, and be sure to give plants a regular feed. The better nutrition they have, the more likely they are to withstand blight infection in the first place. If growing in a greenhouse, be sure to throughly clean down your greenhouse at the end of the season, and air it well before planting. Try a vinegar/water solution to use as a natural disinfectant – 1 part vinegar to 8 parts water. Also, fill pots or beds with fresh compost before planting in a greenhouse again.