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. 
