FUNGICIDE, fithil-sid (from Lat. fungus, mushroom + etrdere, to kill). Any material that will destroy fungi or prevent the germination of their spores. Fortunately for agriculture, there are a number of substances which may bo employed for this purpose. On account of their destructive influence, copper salts, which form the basis of many fungicides, are used in several of the most important. A few of the commonest and best fungicides are given herewith. When used upon foliage, the liquids must all be applied as a mist-like spray, especially to the under sides of the leaves, where many of the fungi gain entrance through the stomata, and only in sufficient quantity to moisten the surfaces, with out standing on them or running off in drops. Neither should they trickle off dormant wood.
Bordeaux mixture, accidentally discovered in France about 1882, is the best general fungicide known. It consists of a solution of copper sul phate and lime. The corrosive action of the former upon many kinds of foliage is neutralized by the lime, which also makes the mixture more adhesive. The following is considered the best method of preparation: In a wooden vessel dis solve copper sulphate at the rate of one pound to a gallon of water by suspending the salt in a coarse bag just below the surface of the water. It will dissolve more quickly if suspended than if placed at the bottom. In another vessel slake stone lime with just enough water to cover it. This lime should contain little or no magnesium. When slaked, add water until the proportion is one pound of lime to one gallon of water. When needed for use, these two stock-solutions, as they are called, are diluted with water, and then mixed with as much agitation or stirring as possible. The proportions in the final mixture should be six pounds of copper sulphate, four pounds of lime, fifty gallons of water for apply ing to dormant wood and strong foliage, such as apples and currants; for young and for tender foliage, such as peach and plum, an extra pound of lime and twenty-five gallons more of water should be added. To test the neutrality of the mixture, a drop of ferrocyanide of potassium is added to a little of the compound, and if a brown color is observed, more lime must be added; if none, then the fungicide may be ap plied with safety. The stock-solution of copper
sulphate may be kept indefinitely; the lime for only a few days. Since the mixture deteriorates rapidly by the flocculation of lime' particles, it should be mixed fresh for each application.
Amtnoniacal copper carbonate solution is al most as good as Bordeaux mixture, and it is clear, and therefore produces no stain, it is better than Bordeaux mixture for spraying on ornamentals and ripening fruits. It is made by dissolving one ounce of copper carbonate in one pint of ammonia, and adding ten gallons of water.
Rau celeste is an important fungicide, but in inexperienced hands it may burn the foliage of many plants. It is made by dissolving one pound of copper sulphate in two gallons of water, adding one and a half pints of ammonia when cooled, and diluting with water to twenty five gallons.
Copper sulphate dissolved in water at the rate of one pound to ten gallons of water is of great value as a spray for fungi, lichens, algae, etc., upon dormant trees and vines. It should not he used on foliage because of its corrosive action. The seed of oats, wheat, barley, etc., may be soaked in this solution to destroy the spores of smut (q.v.).
Sulphur has an important rank among fungi cides, especially as a remedy for powdery mil dews. in outdoor use it is dusted upon the foliage, but in greenhouses it is generally evapo rated. Either the steam-pipes are coated with it, or it is more rapidly volatilized by heating it in a sand bath over an oil stove. Extreme care must be exercised to prevent ignition, since the fumes of burning sulphur are fatal to plants, as may be seen from their use in ridding green houses of plant growths and spores upon the soil, benches, walks, etc. Of course, when so used, the houses are emptied of useful plants.
Hot water may be applied when nearly boiling to kill certain fungi and insects without injuring the plants. Its more valuable use, however, is for the destruction of smuts of cereals. For this purpose, also, solutions of formalin and of corrosive sublimate may be successfully em ployed. The methods of using these fungicides i will be described more fully in the article on