This section is from the book "Commercial Gardening Vol3", by John Weathers (the Editor). Also available from Amazon: Commercial Gardening, A Practical & Scientific Treatise For Market Gardeners.
It is well known that Bordeaux mixture cannot be used for spraying Peach trees, because, even when diluted beyond the point of being of any value as a fungicide, it yet scorches and destroys the foliage of trees growing in the open; whereas, when the trees are grown under glass, as in this country, the foliage is, as a rule, softer and yet more liable to injury. The leaves of Almond trees and some others also suffer from the application of Bordeaux mixture. A browning or russeting of apples also often results from the use of the above-mentioned fungicide.
In view of these facts, Dr. W. M. Scott, of the United States Department of Agriculture, has, after repeated experiments, devised a fungicide which can be used with safety on trees having delicate foliage, and which, as a fungicide, is nearly of equal value to Bordeaux mixture. The ingredients used are as follows: -
Quicklime ... ... ... 8 lb.
Sulphur ......... 8 „
Water ......... 50 gall.
Place the lime in a barrel, and pour on 1 gall, of water to start it slaking. Then add the sulphur in the form of a fine powder, adding more water to slake the lime into a paste. Continuous stirring is necessary to prevent the mass caking at the bottom. After the violent boiling - which results from the slaking of the lime - is over, which occupies from five minutes to a quarter of an hour, depending on the quick or sluggish acting of the lime, add sufficient water to stop the boiling, and make up to 50 gall, with water when required for use.
Before commencing spraying, the mixture should be strained to remove the gritty particles of lime; but all the sulphur should be rubbed through the sieve. The mixture should be kept well stirred when spraying, as it settles rather quickly.
Paris green, for the destruction of insects, may be mixed with this fungicide when used for spraying Apples, but should not be used for Peach trees. Paris green may also be added to Bordeaux mixture.