Wednesday, 5 August 2009

The B word

It's like mentioning that Scottish play backstage. The 'B' word on the allotments brings fear into the hearts of all.
Two days ago I received an email from the Allotments Association warning of blight on the allotments. Recommending Spraying with Bordeaux mixture. Warning not to compost any of the plants but destroy them.

So let me tell you briefly about blight. It is caused by the fungus Phytophthora infestans. It produces sporangia on infected leaves and fruit which love moisture and riding in the wind for hundreds of miles infecting potatoes and tomatoes alike. You can spray the plants with a copper based fungicide (Bordeaux Mixture) or mancozeb (Dithane) both are nasty chemicals. I checked on a couple of forums about blight yesterday and read that Bordeaux was acceptable by organic standards.

Off I went and got this horrid bottle of blue powder read on the bottle "NOT GOOD FOR THE ENVIRONMENT" - strong words, also they were strong warnings about harming marine life. As I got to the allotments I saw my friends, 'the vegetarians' wheel-barrowing off their tomatoes - some of the first to be noticed with the dreaded blight. They showed me other plots that had it. Pointing out the brown marks on tomatoes etc. They said that mine looked great and no sign of any nasty blight. I was encouraged to 'save' then with the Bordeaux mixture. Regrettably, I very grumpily mixed up the solution and sprayed all my plants. Just to reiterate, I do not have any blight on my tomatoes (yet!)

I was miserable when I left the plots. What have I done? Sprayed some terrible poison on to my plot to save tomatoes that now I'm not sure I want to eat!! What should I have done? Picked all those little tomatoes (most are still small) and made chutney, and composted the plants? My innocent tomatoes are now all blue. And me all blue too.

And to make matters worse when I trawled the web looking for more info on blight last night, I find that bordeaux mixture is not accepted in organic growing and is banned in large scale use. I do not know what or who to believe. I shall fall back on RHS advice I think.

To quote the RHS website:
Tomatoes grown under glass are not always infected. Plants likely to be attacked - especially outdoor tomatoes - require protective sprays of mancozeb (Dithane) or copper (Murphy Traditional Copper or Vitax Bordeaux Mixture). Apply these before the symptoms are seen as a protection against attack. They will not totally prevent infection, but slow it sufficiently to save crop.