Controlling Disease in the Organic Garden

The main diseases in the organic garden are fungi, moulds and mildew, and rust. To control potato and tomato blight, black spot on roses, beans and peach leaf curl use Bordeaux mixture.

Bordeaux fungicide was discovered in 1882. In Medoc in southern France, many acres of grapes are grown. Little boys used to snatch and carry off the grapes which grew by the roadside. (They were hungry little boys.)

The owners of the vineyards, becoming increasingly annoyed, had resorted to spattering the broad green leaves of the vines with a lime and water slurry to resemble bird droppings in the hope that this would give some protection from the 'light-fingered' boys. Some owners, a little more vindictive, added some bluestone, a substance well-known to be poisonous. This blue-white, sickly-looking concoction would stick to the grapes and foliage even through the heaviest rainstorms.

The summer of 1882 was particularly wet, and mildew rotted the grapes, threatening to destroy the very vines themselves. Late that season, Dr Pierre Millardet, a professor of botany, was inspecting the devastated vineyards in the area. He noticed that a few plants near the roadway were healthy, and heavy with well-ripened grapes. Those farther back in the vineyard were defoliated, and the grapes were shrivelled, rotten, or unripened.

Dr Millardet learned of the composition of the concoction that remained splattered on the sound leaves and fruit During the next two years, he experimented with mbdures of lime, iron, and copper salts but found that the original combination was best. He then worked out the most effective proportions and published his findings in 1885, naming the new spray 'Bordeaux mixture'.

The new fungicide was later improved with the addition of copper sulphate. Although found by chance, it is of course still in use today.

Baking soda in a mixture of 250 g of soda and 125 g of pure soap dissolved into 11 litres of water will control most mildews and rusts.

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