170. Report of State Board of Horticulture. 



five days eleven per cent of its scales; and No. 43, similiarly exposed, lost 

 fifteen per cent. 



The check trees 40 and 41, on the other hand, kept without treatment 

 of any kind, lost within five days but four scales out of five hundred 

 counted. 



It was further apparent from observations made in the field that a brief 

 but hard and dashing rain would detach many more scales than a light 

 rain longer continued, and that a fine misty rain did not loosen the 

 scales at all. 



PRACTICAI. CONCT^USIOISS. 



The foregoing described observations and experiments go to show that 

 the Oregon wash of lime, sulphur, and blue vitriol, is a valuable in- 

 secticide for winter use in the climate of Illinois for the destruction of 

 the San Jose scale; that its full effect will be produced in about a week; 

 and that frequent short rains will not noticeably diminish or delay its 

 action, even when they come within the first five days after the in- 

 secticide treatment. It is entirely harmless to any leafless tree, and 

 hence maj' be freely used in winter (but in winter only) for all kinds of 

 trees, shrubs, and vines. 



The California wash of lime, sulphur, and salt, prepared as described 

 previously, is a little less effective than the Oregon wash as a scale 

 destroyer, and is considerably more likely to deteriorate after application 

 if exposed to rains within the first few days. Otherwise its effects and 

 characteristics are very similar to those of the Oregon wash. 



It should be generally known that both these washes corrode brass and 

 copper rapidl}', and that consequently an iron pump may be used to better 

 advantage in spraying them than one made in part of brass. 



With respect to the comparative effectiveness of these washes and the 

 better known whale-oil soap and coal-oil mixtures we have as yet no 

 accurate knowledge. There is nothing to indicate, however, that the 

 former are less effective here than on the Pacific Coast, where they seem 

 to have been found very satisfactory in the hands of the ordinary orchard- 

 ist for the destruction of the San Jose scale. Over both the latter applica- 

 tions they have the very great advantage that they are harmless to the 

 tree, and that they do not endanger the crop of the following year. They 

 are also decidedly cheaper than either the whale-oil soap or the kerosene 

 emulsion. In our winter's work the cost of the materials for these various 

 mixtures has been $1.12 per hundred gallons of the Oregon and the Cali- 

 fornia washes; $2.80 per hundred gallons of kerosene emulsion, diluted 

 to contain twenty per cent of kerosene; and $6.-50 for the same quantity 

 of the whale-oil soap solution, at the usual strength of two pounds to the 

 gallon of water. 



