204 



JOURNAL OF ECONOMIC ENTO^IOLOGY 



[Vol. 8 



THE INSECTICIDAL PROPERTIES OF VARIOUS SULPHIDES 

 AND POLYSULPHIDES 



By P. J. Parrott and W. J. Schoexe 

 (Ahstract) 



Recent years have witnessed the appearance on the market of a 

 large number of sprajdng mixtures which derive their efficient prop- 

 erties from sulphides and polysulphides of sodium, potassium, cal- 

 cium and barium. IMost of these are in liquid form, but three 

 preparations in a powdered or granular state, containing sulphides of 

 sodium, potassium and barium respectively as their chief constitu- 

 ents are now offered for sale. It appears that methods for obtaining 

 calcium sulphides in dry form have been devised, but so far only 

 liquid preparations of these compounds are handled by dealers in 

 spraying supplies. The amount of sulphur in proprietary insecti- 

 cides containing sulphides and polysulphides of the different bases 

 varies greatly, ranging for the sodium preparations from 1.79 to 58.92 

 per cent; potassium, 2.39 to 38.72 per cent; calcium, 3.97 to 26.40 

 per cent, and barium 16.54 to 44.0 per cent. 



The variation in amounts of sulphur in the commercial mixtures 

 reveals a need of definite information as to the comparative insectici- 

 dal properties of the foregoing sulphides as a basis for safe and specific 

 recommendations. To obtain data as to the relative merits, experi- 

 ments have been conducted for the past two jesLVS in which the com- 

 pounds have been tested on the basis of their sulphur content, the 

 sulphides and polysulphides of the different bases being used at vary- 

 ing strengths to give similar ratios of sulphur respectiveh^ in the chlute 

 mixtures. 



In experiments against the San Jose scale, using the compounds at 

 the rate of four and three-fourths ounces of sulphur to a gallon, there 

 were variations in effectiveness on individual trees, especially in apple 

 orchards, which were, however, fairly distributed among the various 

 plats. As gauged by blemishing of fruit, production of young scales 

 and infestation of new wood, it was difficult to perceive that one prep- 

 aration had any appreciable advantage over another. If the com- 

 pounds do really differ in effectiveness, these results suggest that the 

 differences in efficiencies are not great and apparenth^ are such as 

 could easily be overcome either by more thorough sprajdng or b}^ slight 

 additions to the sulphur content of the chlute mixtures or by the in- 

 corporation of inexpensive substances to increase toxic properties. 

 The work in general so far points to the conclusion that the strength 

 of a preparation with regard to its sulphur content is a more impor- 



