INSECT PESTS OF OHIO SHADE AND FOREST TREES 203 



In orchard spraying the lime-sulphur sprays are used quite 

 extensively in a very dilute form during the summer months when 

 the trees are in foliage as a control for certain fungous troubles; 

 but in street and park v^ork the present demand for such work is 

 negligible, and, to the writer's knowledge, the mixtures are never 

 used for this purpose. 



The question is often raised whether an oversupply of lime- 

 sulphur can be carried over from one .season until the next and 

 retain its vital properties, also whether freezing injures the solu- 

 tion. In many instances there seems a partial deterioration when 

 the mixture is held over winter since one frequently finds a con- 

 siderable quantity of amber crystals in the bottom of the barrel. 

 If such a mixture is used, it should not be diluted so heavily as 

 normal mixtures. Freezing does not seem to injure the mixture 

 unless the process opens up the container and causes leakage or 

 free access of air. The mixture when stored should always be 

 kept in air-tight containers. 



Dry or 'powdered compounds of sulphur. — Powdered sulphur 

 compounds are of recent origin and have arisen to fulfill the demand 

 for a spraying material of a more concentrated nature than the 

 liquid lime-sulphur concentrate — one more convenient to handle 

 and lacking the disagreeable tendency to leak out of the container 

 which the liquid concentrate unfortunately possesses. They are 

 proprietary materials, each with its individual formula to be fol- 

 lowed in its preparation for use ; hence no instructions of a general 

 nature can be given except to say that they are dissolved in water 

 and applied as a spray. No dry material to be applied as a powder 

 has yet been devised for scale control. 



The efficiency of this class of materials for the purpose in- 

 tended (the destruction of the San Jose scale, scurfy bark louse, 

 etc.) is by no means as thoroughly established as that of the liquid 

 spray, and in some cases, the cost per gallon of diluted spray is 

 greater than that of comparative strengths of the liquid concentrate 

 or the home-boiled solution. The Station has tested two of these 

 materials which have yielded satisfactory results. These were: 

 "The Soluble Sulphur Compound," which is not a lime sulphur but a 

 soda sulphur, and "Barium Sulphur," which as the name signifies 

 is a compound of barium and sulphur. Both materials seem fairly 

 consistent chemically, but the Soluble Sulphur Compound is prone 

 to deteriorate unless the container is kept tightly closed. When 

 deteriorated the powder loses its bright yellow cast and becomes 

 dirty white in color. Moreover, it increases greatly in bulk, some- 

 times swelling the containers badly, even to bursting the seams* 



