204 OHIO EXPERIMENT STATION: BULLETIN 332 



In addition to the two dry compounds just discussed, a dried 

 preparation of true lime-sulphur, which has recently appeared, has 

 been tested one season. The findings attending the work were not 

 sufficiently conclusive, however, to warrant a statement of results. 



The soluble or miscible oils. — The soluble or miscible oils, as 

 the name suggests, mix readily in water. When so combined they 

 form a white, creamy, oily spray which possesses good spreading 

 and penetrating powers. The standard brands now enjoy the 

 reputation of chemical uniformity and constancy of performance. 

 These oils seem destined to serve an important mission in the field 

 of shade-tree spraying, and particularly in the treatment of trees 

 growing under city conditions proper. They are used extensively 

 in the treatment of hibernating insect forms when the tree is 

 dormant, principally for the control of scale insects. They should 

 never be used as dilute summer sprays for the control of plant lice 

 and other insect forms when the tree is in foliage. Some peculiar 

 quality in the spray not yet understood causes severe foliage injury. 



Two principal facts contribute toward assuring the soluble oils 

 an important role in shade-tree spraying. In the first place, some 

 of the more important shade-tree scales, as will be pointed out later, 

 are not amenable to treatment with the sulphur sprays ; and, in the 

 second place, the oils are less likely to mar the paint of buildings 

 than are the sulphur sprays. 



In city shade-tree spraying, where the tree to be treated fre- 

 quently stands on a narrow street or close to buildings, it can hardly 

 be sprayed thoroughly without some of the mixture being thrown 

 on, or the drift blowing on the buildings. Lime-sulphur combines 

 chemically with the paint, forming a dark smudge if the building 

 is light in color, and the smudge cannot be washed off after the 

 action has been thorough. The miscible oils do not possess this 

 property. If perchance a nearby building is soiled, because of the 

 ready solubility of the material the paint may be quickly cleaned 

 merely by directing a stream of water from the hose upon it. 



In most instances the miscible oils are used at the rate of 1 

 gallon to 15 of water, though some investigators report it being 

 necessary to use 1 gallon of oil to only 12 gallons of water in order 

 to get killing results. 



Used at the rate of 1 to 15, under normal price conditions, the 

 miscible oils cost more per gallon of diluted spray than most other 

 scale-destroying sprays. However, because of their superior 

 spreading properties, less material is necessary for covering a tree; 

 and when this point is taken into consideration, in the end, the 

 miscible oils are but slightly more expensive than other materials. 



