Fruit & Vegetable Gardening

Tomato blight – How to prevent

Tomato Blight is becoming increasingly common in the allotment garden, how do we prevent it from effecting our tomatoes and potatoes?

Tomato blightBlight is an extremely common disease that affects tomatoes and potatoes. It can be easily identified as leaves and fruit start to turn yellow and then black within a matter of days. You may also notice white mold ‘threads’ on the underside of leaves.

The onset of blight is the allotment gardeners worst nightmare and can totally devastate a crop with very little warning. It is noticeably worse in wet weather

What to do if your tomatoes develop Blight

Firstly (and this applies also to potatoes), pull up and destroy all affected plants. Do not compost them as this will only spread the problem as the fungal spores will transfer to the compost to wreak havoc another season. Burning is the best method of containing blight. There really is no reasonable hope for a blight infected tomato.

How to prevent Blight

  • Never grow tomatoes or potatoes on the same spot for at least three years. Crop rotation is a good method for avoiding many diseases and pests.
  • If you are growing your tomatoes on an allotment, ask your neighbouring plot holders where they grew their tomatoes and potatoes last year as it is a good idea to plant your crop as far as possible from last year’s crop.
  • Before blight starts, spray your crop with copper fungicide in June/July and then repeat a few weeks later.
  • There are a number of blight resistant varieties of tomato on the market such as ‘Ferline’ or ‘Totem’.
  • If you are growing tomatoes in a greenhouse, then ensure that there is plenty of ventilation. This will minimise the chances of blight infection.

By James Middleton

An obsessive gardener since 1982. Day-time job - web designer and developer and University lecturer.

4 replies on “Tomato blight – How to prevent”

Thanks for info, great stuff. What about ties and canes used for support. Should they also be burnt?

Good question. I’d suggest washing them thoroughly with a detergent, Jeyes fluid or disinfectant and give them a good airing to allow them to dry out. Blight spore are airborne, so don’t worry too much about this as they require living material to survive on. Good garden hygiene is always required. I’d also suggest that next year, you opt for a blight resistant variety like Ferline.

I cleaned my greenhouse with Jeyes Fluid, sprayed into all the nooks and crannies with the knapsack sprayer I normally use for weed control. The glass house smelled like a well tended public toilet for a few weeks afterwards so do this very early in the season (unless you like that smell!)

I still ended up with blight on my toms but have put this down to poor ventilation within the green house. The only plant unaffected was the one adjacent to the roof vent so next season I’m going over the top and putting a louvre vent at each end of the green house and I’ll probably use a copper based spray Jub/July time.

I’m growing in 25 litre buckets (also sterilised with Jeyes) filled with cheap growbags. I feed Wilko tomato food and Epsom salts once a week (having suffered with a Magnesiun defficiency last year. I washed everything in Jeyes including the trowel I used to plant my seedlings and the trays I grew the seedlings in.

Sounds like your working hard to fight the blight! Yes, good ventilation is essential. Blight is airborne and will no doubt find it easier to colonise a humid environment. Having a green house with more than one window is a good way of ensuring plenty of air movement.

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