This section is from the book "The Gardener V1", by William Thomson. Also available from Amazon: The New Organic Grower: A Master's Manual of Tools and Techniques for the Home and Market Gardener.
A correspondent, in your last issue, complains of his Rose-trees being attacked by mildew. Some few months ago, I was asked by a nurseryman if I could not make him some composition for checking it; and as dusting with flowers of sulphur is a somewhat tedious and wasteful use of material, I hit upon the idea of dissolving sulphur in alkaline, and thus use it as a dip or wash. I am of opinion, so far as a few experiments have gone, that sulphur is an effectual antidote to mildew - provided it be properly applied. Perhaps the following may be of some use to your many readers. Take, say, 1 quart of strong alkaline (which you can buy at a manufacturing chemist at l 1/8d. per lb.), and add to it 1 quart of water. Pour the alkaline solution into a glass or earthenware vessel, and bring it to a boil. Add, by degrees, flowers of sulphur (keeping the mixture well stirred); add sulphur till you can see that the alkaline will not dissolve more. This you will know by the sulphur depositing at the bottom of the vessel, or the mixture looking muddy. Allow to settle, and on cooling, pour the clear liquid (which is a full deep brown) into bottles, which ought, for its better preservation, to be corked. It is now ready for use. Take half-a-pint of this solution, and add it to 1 gallon of water.
You can now either dip your plants or syringe them, whichever is the most applicable. Tobacco-water could be added - if it is of any use, which is doubtful, besides adding to the expense. The sulphur, although dissolved in the alkaline, is only loosely held, so that when plants are syringed or dipped and exposed to the air, the sulphur deposits in most minute particles, and by that means easily gets at the enemy. The strong solution is a powerful caustic, and care ought to be used in handling it. Those who are desirous of trying the above, and have not the requisite apparatus, might get it made at any working druggist's or chemist's. E. C. S.