Tomato blight and what to do to avoid it.

Sadly, tomatoes are remarkably prone to viruses and diseases:

The first cause may be you! It’s because you’ve been growing tomatoes, or plants in the same family (peppers, aubergines, even potatoes), on the same site or in the same greenhouse soil for years on end, leading to the actual soil becoming infected. This can cause your tomatoes to develop almost every symptom of almost every other virus, pest or disease, such as mottling, rolling, distortion, discoloration, drop and curl! Before asking any deeper questions, aks yourself if you’ve rotated your crops properly on a four year pattern. If you could be guilty of rotation failure, start doing so immediately and in a greenhouse grow your tomatoes in pots or bags while you transfer the old soil outside and bring in some fresh. Tomato blight is a horror and it sits in the soil, transmitting itself to each new generation, and can spread from potatoes so if you have potato blight, watch out for your tomatoes and clear the site thoroughly.

Rapid changes in temperature can lead to inward-curling leaves. For example if the morning feels chilly to you, but you’re sweltering by noon, you’ll almost certainly see inward curling leaves on your tomatoes – try to shield them from these extremes with a bit of shade and shelter.

Something that isn’t a problem but often appears to be is the browning off of old leaves. These leaves at the bottom of the plant will go yellow and brown and droop. It’s nothing to worry about, they have just spent all the starches contained in them in fruit production, you can leave them alone or nip them off as you please.

Irregular watering makes tomatoes split, especially at the end of the season when there are fewer fruits on the plant and they fill up with water. At peak growth each plant can need about a pint of water per day, and those in growing-bags and pots need frequent watering – but you need to think about how many fruits you’ve removed and adjust watering accordingly. Blossom end rot is not a disease, but a disorder caused by lack of calcium resulting from inadequate or intermittent watering. If the soil is allowed to dry out, the roots are unable to absorb nutrients effectively and if fertiliser is added to dry soil the nutrients are too concentrated for absorption by the plant and so it develops splits in the fruit.

Posted by The Allotment Blogger on Wednesday, June 11, 2008


Anonymous Anonymous said...

Has anyone yet had tomato blight
22 august 08

August 22, 2008 at 1:04 AM  
Blogger The Allotment Blogger said...

so far, so good. Not only is there no tomato blight at home but I haven't heard of any on the allotments either - nor is there any blossom end rot in pumpkins or gourds this year which is amazing, given the wet conditions and variable sunshine that we've had this summer. There have been some reports of tomato plants crisping on the leaves and a lot of that seems to be related to this dodgy manure that some allotment sites purchased. Have you got the dreaded blight then, anonymous?

August 23, 2008 at 4:22 AM  

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