MEANS OF CONTROLLING INSECTS 



45 



emulsion, which can then be diluted with water. 

 The emulsion is made by dissolving J pound of soap 

 in 1 gallon of hot water, then adding 2 gallons of 

 the oil and thoroughly agitating the mixture into 

 a stable emulsion. This should be diluted with 3 or 



Fig. 69. Hiagara carbonic acid gas sprayer. 



4 parts of water for scale insects and with about 

 twice as much water for plant-lice and other suck- 

 ing insects. Pumps have been designed for combin- 

 ing the oils and water into a good mechanical emul- 

 sion, but usually the percentage of oil can not be 

 satisfactorily controlled. 



So-called soluble or miscible oils which quickly 

 emulsify with water are now made and are very 

 effective against scale insects. 



A lime, salt and sulfur mixture (often without 

 the salt) is a very effective and safe spray to use 

 on dormant plants for the San Jose scale and the 

 peach leaf-curl fungus. This "wash" is made by 

 boiling for about an hour 15 pounds of flowers of 

 sulfur and 20 pounds of stone lime in 50 gallons of 

 water ; by using about 6 pounds of caustic soda 

 this " wash " can be made without boiling and is 

 nearly as effective, but costs more. 



Fnmigaiion. 



Both sucking and biting insects succumb to the 

 fumes of carbon bisulphid or to hydrocyanic acid 

 gas. 



Carbon bisulphid is largely used in killing insects 

 infesting stored grains or seeds. It is poured into 

 shallow dishes set on top of the grain in tight bins, 

 or it may be sprinkled over the grain. The fumes 

 are heavier than air and sink all through the 

 grain ; as the fumes are explosive, no lights should 

 be near. A little of the liquid poured on clothing 

 stored during the summer will kill the destructive 

 clothes moths. Cucurbitaceous vines have been 

 covered with cloth and successfully treated for 

 plant-lice with carbon bisulphid. 



Hydrocyanic acid gas is generated by dissolving 

 cyanide of potassium in sulfuric acid and water. 

 It is used largely under tents by the citrous 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 insect's, 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, J 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 fino 



Fig. 70. Spray rig with steam power pump. 



dust that is blown into trees with powder-guns. 

 This miscalled "dust-spray" is not so effective as 

 the liquid sprays in orchards, as judged by present 

 experiments, and is used mostly where water is 

 scarce and the land is rough. For applying liquid 



