I took a calculated risk this year in planting the number and variety of Tomatoes that I have -- some nine varieties, in all -- and several of them, Cherokees included, are no more than days away from first harvest. Luckily more than half the plants (and most especially the prized and beloved Brandywines) are situated down in the veggie garden -- almost 100m away from the blighty ones, and no signs of Blight down there yet.
Normally if we get a touch of Blight, it only comes around mid-Feb -- our humid season -- but this year has been exceptionally humid exceptionally early, so no real surprise.
As loath as I was, I could see no alternative, and sprayed all the Tomatoes and Potatoes with Bordeaux mixture. I hate the thought, and it is the first time in over ten years here that I have ever had to resort to such drastic measures, but many of these Tomato varieties are "first timers" for us, and heirlooms that I have gone to considerable trouble to source seed for, So I really, really need to save seed from them. The Bordeaux mix seems to have checked the Blight quite successfully for now, but rain is forecast for tonight, so I guess I'll need to spray them all again tomorrow.
We don't have the "luxury" here of a sophisticated "organic growing" supply chain, such as enjoyed in more first world circumstances, so I was not able to simply go out and buy Bordeaux mix. Actually it is really simple to make, and very much cheaper than commercial preparations:
Into 9 litres water, dissolve 100g Copper Sulphate. In a little water (a cup or so) dissolve 100g quicklime (a.k.a. "builders lime" -- very cheap at building-supply stores.) Be careful to add the lime slowly to the water, and not the other way around, as the reaction when they mix generates considerable heat. Pour the lime-water mix into the Copper Sulphate mix and stir well. That's your Bordeaux mix. Spray it thoroughly onto the affected leaves, stems and fruits. Any badly affected leaves/fruits should be removed from the plant and burned immediately. Also avoid planting Blight-prone plants in the same place again for a few years -- which leaves me with very few options next year!
I hate this solution! I firmly believe that the soil-resident fungi are key players in liberating nutrients for plants, and always take an active soil-fungus population as a sign of good soil health. Bordeaux mix can only affect these badly.
Interestingly, though, the Blight struck in very new beds -- first developed last year -- where the soil is still very heavy, cloddy and way out of balance. In the veggie garden, where beds are much better established and much more mature, even quite Blight-prone varieties are still healthy and strong. Evidence that the soil is supporting their needs much better than the new beds?