ORCHARD SPRAYING EXPIlRIMI^NTS. 7 1 



sulphur and bordeaux mixture and this other form of damage, 

 so markedly different, so distinctly localized and entirely absent 

 on trees sprayed with bordeaux and lead arsenate. Evidently 

 the answer must be sought in the reactions of the arsenates and 

 the sulphur sprays.* 



Relations of Density of Concentrate to Injury. 



The degree of injury to fruit and foliage varied only in a 

 general way with the density of the concentrates. Allowing 

 for the factor of experimental error, the results are in accord 

 with the present practice of increasing the dilution with the 

 density. 



CONCI^USIONS. 



The experiment here recorded is the result of the first sea- 

 son's work and should be regarded as preliminary rather than 

 the basis for final conclusions. In general the data presented 

 show that lime-sulphur preparations may be efficiently used as 

 summer sprays, and that with weather conditions liable to pro- 

 duce spray injury lime-sulphur does less damage than bordeaux 

 mixture both qualitatively and quantitatively. 



Further data are needed regarding variation in the effect of 

 sulphur sprays on different varieties. Other questions are those 

 concerning the minimum effective dilution and the action of dif- 

 ferent arsenicals in combination with them. 



Arsenate of lead proved as effective with lime-sulphur as with 

 bordeaux mixture. The use of a neutral lead arsenate is rec- 

 ommended in order to reduce any tendency to arsenical injury. 



"Sulfocide" with lead arsenate gave unfavorable results on 



* NoT^. — This is indicated by tests made by the chemists of 

 this station. "Sulfocide" and an acid arsenate of lead used in the 

 orchard experiments were mixed in the dilutions used in spraying, and 

 allowed to stand. At the end of half an hour loo cubic centimeters of 

 the mixture after filtering showed 94 milligrams of soluble arsenious 

 oxide. After standing for three days an equal volume yielded 104 

 milligrams, largely in the form of sodium arsenate. 



The same test was made with the lead arsenate and one of the com- 

 mercial lime-sulphur concentrates. Practically no arsenic was found 

 in solution. Nevertheless the calyx injury on the commercial lime-sul- 

 phur plots must be ascribed to a reaction between the concentrate and 

 the arsenate. 



