8 MISSOURI AGRICULTURAL EXPERIMENT STATION BULLETIN 176 



reasonably fine spray, yet one which will penetrate into protected places. The 

 spray solution kills by contact so each scale must be touched. Spray thoroughly 

 therefore and be sure the tips of all twigs are thoroughly coated. Spray all 

 the way thru the tree from all angles. Blotching of fruit is often the first 

 signs of infestation the grower observes. However, other insects may cause 

 blotches on fruit so this is not always a sign that the scale, is present. In case 

 of doubt send twigs and blotched fruit to the Agricultural Experiment Station 

 for examination. 



In the nursery the use of dormant sprays is not sufficient to insure against 

 the possibility of spread of scale on nursery stock. Dormant sprays may con- 



FiG. 8. San Jose Scale. Spraying infested peach orchard, using small barrel outfit 



trol the pest but it is humanly impossible to hit and kill every individual. For 

 this reason inspection laws require the destruction of visibly infested trees and 

 the fumigation or dipping of all other susceptible trees or shrubs before dis- 

 tributing them. For fumigation use an air-tight room and hydrocyanic acid 

 gas. Subject the trees to the gas for from forty to sixty minutes. The gas 

 is made by using one ounce of potassium cyanide 98% or sodium cyanide 130%, 

 one ounce of commercial'sulphuric acid, and two or three ounces of water for 

 each one hundred cubic feet of space. If the stock is dipped, a miscible oil 

 diluted with twelve parts of water has given best results. In spite of the most 

 careful work of inspection and treating of nursery stock there is the chance 

 that some scale may escape, resulting in infestation in the orchard where trees 



