■ ORCHARD SPRAYING EXPERIMENTS. 39 



Prof. J. P. Stewart* as a cheaper and chemically more stable 

 form of arsenic to use. Stewart's data indicate a slower rate of 

 decomposition of this material in combination with lime-sulphur 

 solutions than either Paris green or arsenate of lead. Its ad- 

 hesive properties appear to be less than the latter's. No field 

 experiments are cited to support the recommendation. Experi- 

 ments of the season just past have shown that arsenite of lime 

 is less desirable than arsenate of lead.f 



Whatever the differences of opinion regarding the actual 

 method of injury, the fact accepted by all investigators in this 

 field is that copper is the injurious element in bordeaux mix- 

 ture. Recognizing this fact, an effort has been made in recent 

 years to eliminate the copper containing solutions in spraying 

 plants of proved susceptibility despite their recognized high 

 fungicidal efficiency, and to find a satisfactory substitute. 



Sui^PHUR AND Sulphur Compounds as Fungicides. 



In this effort attention has chiefly been turned to solutions 

 of sulphur in chemical combination. 



Pure sulphur in powdered form has long had a place among 

 fungicides. Flowers of sulphur has been used for the control 

 of powdery mildew of the grape {Uncinula necator (Schw.) 

 Burr.) and is effective in greenhouses against rose mildew 

 (Sphaerothea pannosa (Wallr.) Lev.). A lime-sulphur paste 

 is also mentioned by Duggar^ as a means of control of this 

 greenhouse fungus. 



"Curiously enough, however, as early as 1833, before the gen- 

 eral use of fungicides. Dr. Wm. Kenrick§ recommended for 

 mildew on grapes a mixture of sulphur (i^ pints), quicklime 

 (a piece the size of the fist) and boiling water (2 gallons). 

 This mixture, after cooling, was diluted with cold water and 



*Stewart, J. P. "Concentrated Lime-Sulphur. Its Properties, Prepar- 

 ation and Use." Annual Kept. Pa. State College (1908-1909) Part II, 

 pp. 292-293. 



fMr. L. Caesar of the Ontario Agricultural College reports severe 

 injury in some cases this past season from the use of arsenite of lime. 

 In general the results were markedly inferior to those obtained with 

 lead arsenate. 



JDuggar, B. M. "Fungous Diseases of Plants" (1909), p. 90. 



§The New American Orchardist (1833), P- 328. 



