28 MASS. EXPERIMENT STATION BULLETIN 201. 



Formula. — The 8-8-50 formula is now used almost exclusively (8 

 pounds of quicklime, 8 pounds of sulfur, 50 gallons of water). 



Physical and Chemical Properties. — This is a mechanical mixture, or, 

 at most, there is only a minimum amount of chemical union between the 

 lime and sulfur. In explanation of the part pla^^ed by the lime, Scott (41) 

 says: "The intense heat seems to break up the particles of sulphur into 

 about the physical condition of precipitated sulphur, and the violent 

 boiling makes a good mechanical mixture of the lime and sulphur. The 

 finely divided sulphur is depended upon for the fungicidal action rather 

 than the sulphids in solution." The lime also gives adhesive qualities. 



The result, then, is the same in the end, whether the commercial lime- 

 sulfur or the self-boiled is used, — sulfur in a finely divided form is de- 

 posited on the leaves, and the fungus is killed or checked in its development 

 as described above (page 26). 



(3) Sulfur Dust. 



The use of sulfur dust as a protective application was first begun in New 

 York State and most energetically pushed by Whetzel, Reddick, Blodgett 

 et al. of the Cornell Experiment Station. Since its beginnhig in New York 

 State in 1912, experiment station workers in Michigan, Georgia, Illinois, 

 Virginia, West Virginia, Maryland, Nova Scotia, and Ontario have con- 

 ducted orchard tests with the dust as a possible substitute for the lime- 

 sulfur and lead arsenate spray. The published results from New York, 

 Michigan, Illinois, Nova Scotia, and Ontario indicate an efficiency equal 

 to that of lime-sulfur and lead arsenate for the control of apple scab and 

 codling moth. Virginia and West Virginia workers report satisfactory 

 control of codling moth, but find it unsatisfactory for black rot, bitter 

 rot, rust and scab of apples, and (in Virginia) for brown rot of peaches. 

 Peach dusting experiments in Georgia and West Virginia indicate an 

 efficiency against scab and curculio equal to that of the suKur spray, and 

 slightly less control for brown rot. Results in Maryland are less favorable 

 to control of orchard fungi by dusting than by spraying. Whether it is 

 better to dust than to spray and just what diseases can be better con- 

 trolled by dusting are questions that have by no means been fully answered. 

 Dusting has many opponents as well as advocates among both scientists 

 and practical growers? No great body of experience has yet been developed 

 in Massachusetts, and lacking this, the question cannot be satisfactorily 

 answered. 



Formulas. — The sulfur dust is still in the experimental stage, and the 

 proportion of sulfur to lead arsenate or to inert "fillers" has not become 

 standardized. The most used formula calls for 90 parts of very finely 

 ground sulfur to 10 parts of the fluffy type powdered lead arsenate. 

 "Fillers," such as hydrated lime, "terra alba," etc., have been used in some 

 places. The material may be bought ready-mixed or mixed with machine 

 at home. Various types of dusting machines for application are now on 

 the market. 



