42 BULLETIN" 278, U. S. DEPARTMENT OF AGRICULTURE. 



mercury bichlorid, zinc chlorid, zinc oxid, and zinc sulphate. While 

 some of these compounds gave more or less satisfactory results, they 

 were not of sufficient promise to warrant further testing. 



SODIUM AND POTASSIUM SULPHUR SOLUTIONS. 



Caustic soda and caustic potash (homemade and commercial) were 

 combined with sulphur for the control of the San Jose scale. Cer- 

 tain of the solutions proved to be generally satisfactory as scalecides, 

 in some instances equaling lime-sulphur solution. Such solutions 

 can be readily prepared at home without the use of heat. 



CONCLUSIONS. 



During the course of the experimental work information on the 

 value of many compounds and combination sprays has been se- 

 cured. Several of the materials proved to be less valuable than 

 those now in common use, owing to their slow killing effect, to their 

 injury to foliage, to their cost, or to their incompatibility. While 

 many of the compounds proved to be impracticable for insecticidal 

 purposes, certain new spray materials and combinations were used 

 with success. Since the prevention of fungous diseases is intimately 

 associated with insect control, many of the insecticides were tested 

 with a fungicide in order to ascertain the results of such a combina- 

 tion. 



Arsenate of lead proved to be the most consistent and valuable 

 stomach poison tested, giving satisfactory results throughout the 

 experimental work. 



Arsenate of lead is equally effective in either the paste or pow- 

 dered form. 



Triplumbic arsenate of lead is less rapid as a poisoning agent than 

 diplumbic arsenate, but is safer for use on tender foliage. 



Arsenate of lead may be combined with nicotine solutions and 

 lime-sulphur solution for the control of certain apple chewing and 

 sucking insects, and fungous diseases. 



For the control of certain sucking and chewing insects arsenate of 

 lead may be combined with kerosene emulsion. 



Arsenate of lead, kerosene emulsion, and lime-sulphur is an incom- 

 patible mixture, due to the formation of an insoluble calcium soap 

 and the subsequent release of free kerosene. In our experience any 

 combination containing lime-sulphur and soap should not be used, 

 owing to the formation of an insoluble calcium soap. 



Arsenate of lead should not be mixed with sodium sulphid com- 

 pounds, since the soluble sodium arsenate formed is destructive to 

 leaf tissue. 



Arsenate of lead combined with a commercial barium tetrasul- 

 phid gave satisfactory control of the codling moth and caused no 

 foliage injury in the experimental apple orchard. 



