Hydrocyanic acid gas is generated by dissolving cyanide of potassium in sulfuric acid and water. It is used largely under tents by the citrons orchard ists in California for scale insects, and by many nurserymen for fumigating their stock to kill San Jose scale and other injurious insects. Greenhouses, dwellings, cars and flouring mills have been fumi gated successfully with this gas for the white-fly, household insects, and the flour-moth. The usual formula for fumigating everything but green houses is 1 ounce of cyanide of potassium, 2 ounces of commercial sulfuric acid, and 4 ounces of water for each 100 cubic feet of space ; the fumigation should be continued for half an hour for nursery stock and several hours or all night in buildings or cars. For green house fumigation, to 1 ounce of the cyanide is used at night for each 1,000 cubic feet. This gas is exceedingly poisonous to persons when breathed, causing death instantly.
Spraying methods and machinery.
Many growers of fruits, potatoes and garden crops now include spraying as one of the regular and necessary "farm practices" to protect their crops from insect and fungous enemies. To spray the most successfully requires skill, practice, and some knowledge of the enemies to be fought. Much energy and money is wasted every year in trying to kill sucking insects with poison sprays which they can not eat, or by uninterested laborers who hurry through the more or less dis agreeable job. It is often necessary to success that we follow closely the detailed directions for mak ing the sprays ; for example, it is very essential that dilute and not concentrated mixtures of copper sulfate and lime be poured together in making Bordeaux mixture. Successful spraying is scientific and thus requires the services of faithful, trained men. Only the most thorough work with the best materials and machinery will accomplish the most paying results. To control successfully the San Jose scale, for example, each tiny scale not larger than a pin's head must be hit thoroughly with a powerful insecticide, thrown with force through fine nozzles so as to penetrate every crevice in the bark.
Machinery for the application of insecticides has developed from a bundle of twigs or a broom, through syringes and ill-adapted pumps, to a formi dable array of powder-guns and pumps specially adapted to various conditions and crops. Insecti cides and fungicides are now combined into a fine dust that is blown into trees with powder-guns. This miscalled "dust-spray" is not so effective as the liquid sprays in orchards, an judged by present experiments, and is used mostly where water is scarce and the land is rough. For applying liquid si rays there are little atomizers holding a quart or two with whicl. house plants. small gardens, or a few catO4 nmy be sprayed. Next come the bucket pump and knapsack sprayers, which will be found u-tt.fut ,.n most farms for spraying small areas or Isolated trees in gardens, For several years barrel pumps were much used in all spraying operations, but now large tanks equipped with more powerful pumps in which the power is developed by horses, by steam or gasoline engines, by compressed air, or carbonic acid gas, are mostly used in spraying large areas of vineyards, potatoes and other crops. The horse-power pumps, in which
the power is developed from the wheels by chain or eccentric attachments as the machine moves, give sufficient power to do satisfactory work only on potatoes and similar low field crops. A small compressed-air tank attached to these horse power pumps greatly increases their efficiency for the spraying of small orchard trees and vineyards. The pumps using compressed air for power do very effective spraying of all kinds, but the necessary outfit of several spray tanks, an engine and an air compressor are rather expensive. Steam spraying rigs are heavy but are easily managed, and fur nish cheap and abundant power. Gasoline engines are lighter and are being much used instead of steam power. The tanks of compressed carbonic acid furnish ample, easily manipulated but slightly more expensive power than the engines. Some of the forms of spray rigs are shown in Figs. Good nozzles are an essential part of spray pumps. Several types of spray nozzles are used.
Some, like the cyclone and Vermorel nozzles, pro duce a very fine, funnel-shaped spray. In another type, like the McGowan, the spray is fan-shaped and can be thrown farther. The various modifica tions of the Vermorel type of nozzle are now most extensively used, often several nozzles being grouped at the end of a light rod attached to the spray hose.
The manufacturers of spraying apparatus are constantly improving and modifying their machines so as better to adapt them to the practical needs of the agriculturist. American farmers are un doubtedly the best equipped with insecticidal bat teries, and they are putting up the most scientific and successful fight against their insect enemies.
Literature.
The literature on the means of controlling insects is very extensive and scattered, much of it having to do with controlling specific pests. The reader will find a great deal of interesting material in special articles in the yearbooks, in bulletins and circulars of the Bureau of Entomology and Farmers' Bulletins, of the United States De partment of Agriculture, and in bulletins issued by the federal and state experiment stations of the various states. The following publications should also be consulted : Annual Reports and Bul letins issued by the State Entomolo gists of New York (Dr. E. P. Felt, Al bany), Illinois (Prof. S. A. Forbes, Ur bana) and Minnesota (Prof. F. L. Wash burn, St. Anthony Park, St. Paul), and by the Government Entomologist (Dr. J. Fletcher) at Ottawa, Canada ; Lode man, Spraying of Plants, 1896 ; John son, Fumigation Methods, 1902; Smith, Economic Entomology, 1896; Weed, Insects and Insecticides, 1895; Sanderson, Insects Injuri ous to Staple Crops, 1902.