Tomato blight

What is Tomato Blight?

Tomato blight, also known as late blight, is a fungal disease that wreaks havoc on tomato and potato plants, causing leaves and fruit to turn yellow, blacken, and rot within a matter of days. The presence of white mouldy ‘threads’ or ‘whiskers’ on the underside of leaves further confirms the presence of this dreaded disease.

The onset of blight is an allotment gardener’s worst nightmare, capable of wiping out an entire crop with alarming speed, especially during wet weather conditions. It’s a disease that can spread rapidly, making prompt action crucial to prevent its spread and minimise damage to your precious tomato plants.

When Blight Strikes

If you notice the telltale signs of blight on your tomatoes, swift action is essential. The first step is to remove and destroy all affected plants. Do not attempt to compost them, as this will only serve to spread the fungal spores and perpetuate the blight problem. Burning is the most effective method of containing blight and preventing its spread to healthy plants.

Prevention: Your First Line of Defence

The best way to combat blight is to prevent it from striking in the first place. Here are some effective prevention strategies:

  1. Crop Rotation: Never plant tomatoes or potatoes in the same location for at least three years. This simple practise helps to break the lifecycle of the blight fungus, depriving it of a suitable host and minimising the risk of infection.
  2. Site Selection and Varieties: Choose a well-drained, sunny location for your tomato plants. Opt for blight-resistant varieties like ‘Ferline’ or ‘Totem’ to enhance your crops’ resistance to this disease.
  3. Fungicide Application: Before blight season begins, apply a copper fungicide to your tomato plants in June or July. Repeat the treatment a few weeks later to provide continuous protection from the fungus.
  4. Ventilation in greenhouses: If you’re growing tomatoes in a greenhouse, ensure adequate ventilation to minimise humidity levels and discourage the spread of blight spores.
  5. Moisture Management: Avoid overhead watering, as this can spread fungal spores. Instead, water at the base of the plants to keep the foliage dry.

Remember, vigilance and proactive measures are key to safeguarding your tomato plants from the perils of blight. By following these preventive strategies and acting promptly when signs of blight emerge, you can ensure a bountiful tomato harvest and keep your gardening efforts blight-free.

This Post Has 4 Comments

  1. Vince Johnson

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

  2. James Middleton

    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.

  3. David

    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.

  4. James Middleton

    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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