Tomato Blight in Polytunnel

[John]

My allotment tunnel, which I can’t visit everyday, has mesh on the top half of the end doors and a six inch air gap above. I have been cutting off odd leaves and stems with signs of blight over the last 2 weeks but, going away for a week, I decided to cut back all of the foliage and two plants with the start of blighted stems.

In spite of careful ground watering I find some leaves can be quite damp or even wet in the morning, presumably due to condensation.

Fortunately we have been able to process many (too many?) toms but I am hoping that my drastic pruning and stopping watering will fend off the blight and allow toms to ripen although I doubt they will continue to grow.

Any thoughts on what I have done and any hints for next year?

[Vivian G]

Hi John,
Using a knife or sheares to cut off infected leaves can help spread the infection. So an idea for next year would be to break infected leaves off rather than cutting them.

[John]

Hi Vivian

Thank you for the input. I had been breaking off individual leaves but my more drastic pruning with secateurs was always into clean stem and, after four days away with no watering for over a week, there is no visible blight and I have lots of ripe and ripening tomatoes.

Perhaps even careful watering of the soil can add too much water to the atmosphere and provide conditions where blight is more likely to settle on the foliage.

[charles]

John I think we tend to blame ourselves too much. Recently the air has been incredibly humid esp 20th-23rd, with little sun, so leaves have enough moisture on them, collecting in low pockets, for blight spores to multiply. This morning I was surprised to find blight on even some Sungold tomatoes in the tunnel.
I agree that removing damage will limit its spread, and Vivian’s point about breaking leaves is good, though I sometimes cut.
The weather is drying up now so things will improve, also some cooler nights will slow the spread of blight.

[Author]

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