In the sense in which the word spraying is now used we may say that it is an operation of our day. In commercial fruit-growing centres of California, and indeed of all parts of the Union, spraying for the destruction of insects and lessening injury of plant, tissue by fungi has become almost as necessary as tillage-pruning, and other leading essentials of fruit management. In Europe, France took the lead in this important work. But it was not until the appearance of the downy mildew upon the grape in 1878 that any real advance was made in the way of methodic spraying. Indeed, it was not started until 1882, when Paul Oliver used the solution of water, sulphuric acid, sulphate of iron, and sulphate of copper for fungous diseases of the pear.
In 1882 the writer on a visit to France found spraying with sulphate of copper on the grounds of Sir Henry Vilmorin, south of Paris, and in 1883 Millardet wrote: "Recent observation makes me hope that perhaps the most satisfactory results may be obtained by the use of certain mineral solutions, such, for example, as the sulphate of iron or of copper." But it is singular that the practical use of the discovery was not made until spraying with milk, lime, and sulphate of copper was given along roadways and in exposed places to prevent the stealing of the grapes. The writer in 1882 was surprised to see vines with leaves and fruit covered with a light-blue coloring matter. It was soon found that the vines thus "poisoned" - as the people were led to believe - were the only ones that retained their foliage in the infected districts in 1882.
It was not until 1885 that Millardet gave the formula for making what is now known as Bordeaux mixture, but it was at first applied with a broom. So far as known to the writer the first perfected spraying machines used in Europe were made in the United States.
In the United States the first spraying, or rather sprinkling done with a broom, was in 1860, when the currant and gooseberry worm made its first appearance. A solution of hellebore in water was then used. In 1877 the Colorado potato-beetle had extended over Iowa, and the first remedy used was spraying with Paris green, which was only partially successful on account of its varied purity. The sudden demand for the article led to adulteration to a remarkable extent. In 1877 an agent of Hemanway & Co., of London, visited Ames, Iowa, with a view to securing a trial at the Agricultural College of a waste product of their analine dye-works as an insecticide. In February, 1878, three kegs of the waste under the name of "London purple" reached Ames and were tested in the summer of 1878 by the writer. At Ames the potato-beetle was then at its height of development and destruction. In the fall of 1878 the writer gave in the Iowa Agricultural College Quarterly the following statement: "Last winter the college received for trial a quantity of a material called by the manufacturers London purple, and designed to be used for the Colorado potato-beetle (the potato-bug of common parlance). Upon trial it was found very valuable, killing the old as well as the young insects with great certainty. The virtue of London purple lies in the arsenic it contains, just as in the case of the Paris green. There are, however, several advantages possessed by the new poison over the old, among which are: (1. Seedling Variations) its extreme fineness, permitting it to be mixed with water; (2. Seed Variation of Cultivated Plants) its adhesiveness: when once applied it adheres tenaciously to the leaves; this is due no doubt to its finely divided condition; (3. Commercial Seeds) its purple color enables one always to detect its presence on leaves even when it exists in very small quantity; this will not only guard against accidents, but at the same time be of considerable account in enabling one to always know when it is necessary to make another application; (4. Seed-saving) its cheapness as compared with Paris green."
At that time Hon. John N. Dixon, of Oskaloosa, Iowa, was a trustee of the Iowa Agricultural College and was the owner of one of the largest apple orchards in the State at that time. The canker-worm visited this orchard in 1877. In 1878 he reported as follows in the Iowa Horticultural Report: "My success with these chaps has been so encouraging that I am very willing to talk about it. I mix a pound of arsenic in one hundred and fifty gallons of water, heated in a sort of sorghum-pan concern got up for the purpose. I dissolve the arsenic by boiling in much stronger proportion than this, but I am careful to add water when the liquid is put in the barrels for use, so as to make the proportion as above stated. The pump I use for throwing the water over the trees cost, in Chicago, sixteen dollars. I load the barrels of water in a wagon and drive on the windward side of the row to be sprinkled. I find I can thoroughly poison the foliage by showering from the one side. I first tried the Paris green, but found it expensive and liable to burn the leaves; it is also a dangerous stuff to use. The arsenic water makes a delicate coating of arsenic over the leaves, but the rains soon wash it all off; long before the fruit reaches maturity the last vestige is gone. I showered three thousand trees, when the most advanced worms were about full size; one application killed every one of them, and I have not seen a worm in the orchard since. I tried a solution of concentrated lye; the worms were soon on the ground, but they were soon on full diet in the trees again. The arsenic dodge they can't stand ; in thirty-six hours everyone turns black, and their bodies break like a pipe-stem."
It so happens that the season most favorable for killing the canker-worm is the most favorable for spraying for the codling-moth. Hence in spraying for canker-worm he met with the first great success in destroying the codling-moth. He marketed carloads of apples in Minneapolis in 1878 entirely free from worms or worm-holes. John Smith, an extensive orchardist at Des Moines, and A. E. Whitney, of Franklin Grove, Illinois, made the same discovery in fighting the canker-worm, and Mr. J. S. Woodward, of Lockport, New York, also made the discovery in regard to the destruction of the codling-moth when spraying for canker-worm.
The florists were far in advance of orchardists in the use of insecticides, such as whale-oil soap, potash, pyreth-rum, kerosene, buhach, tobacco infusions, and hot water for insect destruction. The use of kerosene emulsion and pure kerosene and raw petroleum in orchards is not new, especially the emulsion for the sucking and scale insects. It was first used by the florists, and for fighting the currant worm in 1868 and 1870, but its commercial use began with orange-growers in Florida and California as late as 1882. But it was not until 1886 that the formula for scale as now used was generally recommended. Kerosene and raw petroleum were used on house-plants and greenhouse-plants, and on the wounds made by cutting off plum knots, by the writer as early as 1876, and at the Exposition in Philadelphia it was recommended for scale insects by European florists. On the plum-knot wounds it was used freely, but on oleander and other plants infested with scale it was used on the cloth with which the scale was wiped off.
The present use of kerosene and petroleum for scale and other insects by spraying trees in the dormant period dates only from the advent east of the Rocky Mountains of the San Jose scale. At this time (1901) the final effect of drenching trees with kerosene or petroleum prior to leaf expansion is not fully known. Apple and other trees well drenched by spraying two years in succession show clean bark and general thrift not found on unsprayed trees.
Since 1885 the appearance of the apple scab, grape rot, anthracnose, and other fungi in large commercial plantations has led to hundreds of trials at the experiment stations and by private growers of various fungicides. At this time nearly all the experiment stations send out each year spraying calendars giving reliable information up to date. Those interested in a more minute statement of the recent evolution of spraying are referred to Lodeman's reliable book on "Spraying."