INSECTICIDES 53 



and boil gently for one hour. If kettles and fire are used, more 

 than the required amount of water may be used at first, to com- 

 pensate for evaporation, or the volume may be kept constant by 

 adding successive small quantities to hold the mixture at the 

 original level, as shown by a notch on a stick resting on the bot- 

 tom of the kettle, and marked when the mixture first begins to 

 boil. When boiling with live steam the mixture will be more 

 likely to increase in volume than to decrease, so that no water 

 need be added. 



" This concentrate will keep with little change, unless the 

 weather is below 5 F., if stored in filled, stoppered barrels. 

 Even in open receptacles there will be no loss if the surface be 

 covered by a layer of oil to prevent access of air. Each boiling 

 should be tested with a Beaume hydrometer * and its density 

 marked on the barrels or other containers." 



The dilution is based upon the specific gravity as shown by 

 the hydrometer and may be safely made according to the out- 

 line in the above table. 



In making this mixture it is important that only high-grade, 

 pure lime should be used, and lime with less than 90 per cent 

 calcium oxid (CaO) should be discarded. 



9. Self-boiled Lime-sulfur. Self-boiled lime-sulfur has proven 

 to be the only safe fungicide for the foliage diseases of the 

 peach and stone fruits, and is used extensively as a summer spray 

 on pome fruits. As a winter wash for San Jose scale it has not 

 proven as effective as the boiled mixture, but when used as a 

 summer spray for fungous diseases it also has considerable 

 insecticidal value. Its general usefulness as a summer insecticide 

 is in the process of experimental determination, but sufficient 

 results have already been secured to warrant the statement 

 that it will prove of considerable value as a summer insecticide 

 for certain pests, where it is to be used for the fungous diseases 

 of the host plant at the same time. This mixture has been developed 



* These hydrometers, made specially for testing lime-sulfur mixture, may 

 be obtained from the Bausch & Lomb Optical Co., Rochester, N. Y., and 

 other dealers in laboratory glassware. 



