130 JOURNAL OP ECONOMIC ENTOMOLOGY [Vol. 2 



THE SELF-BOILED LIME-SULFUR MIXTURE AS A 

 SUMMER TREATMENT FOR THE SAN JOSE SCALE 



By A. L. QuAiNTANCE, Washington, D. C. 



A self-boiled lime-sulfur wash, that is, cue in which the cooking is 

 done entirely by the heat generated by the slaking of the lime, has 

 been for some years more or less used as a substitute for the well- 

 boiled wash for dormant tree treatments for the San Jose scale. As 

 obviating the necessity for a cooking plant, this self-boiled wash, if 

 effective, would have much to commend it, but unfortunately, in most 

 cases, it has not given satisfactory results in controlling the insect 

 and is, perhaps, now but little used. Analyses of such washes have 

 shown that, as ordinarily made, only a small part of the sulfur pres- 

 ent passes into solution, though the free sulfur present is left in a 

 very finely divided condition. The amount of heat generated by the 

 slaking of the lime will vary considerably, depending upon its purity 

 and as to how the mixture is handled, as the use of hot or cold water 

 in slaking, the length of time the mixture is allowed to stand after 

 slaking, whether the vessel be covered, etc. Anal^^ses of washes made 

 in a way to generate and conserve the maximum amount of heat, show 

 that a relatively high percentage of sulfur may be rendered soluble, 

 approximating in fact the amount obtained in a well-cooked wash. 

 Variations in method of preparation, therefore, could well account for 

 the different results reported by orchardists and experimenters in 

 the use of self-boiled washes. The self-boiled caustic-soda wash, 

 quite a different preparation, has been used more successfully as a 

 dormant-tree spray for the San Jose scale, as the heat from the lime 

 is supplemented by that resulting from the caustic, and the chemical 

 reaction is, furthermore, quite different. 



The supposed causticity of self-boiled washes has had the effect of 

 excluding them from among possible sprays for use on trees in foliage 

 and, although these have been much experimented with by entomolo- 

 gists and others, no one apparently has tried a self-boiled wash as a 

 summer treatment for the San Jose and other scales. The recent in- 

 vestigations of Prof. W. M. Scott, of the Bureau of Plant Industry, 

 of self -boiled lime-sulfur mixtures as fungicides for use on the peach 

 in the control of brown rot and scab, and on apple in the control of 

 scab, bitter rot, etc., have shown, contrary to the general impression, 

 that self-boiled mixtures may be prepared in a way to permit of their 

 use with perfect safety on trees in foliage. This is a very important 

 discovery from the standpoint of plant pathologists, as furnishing a 



