Page 42 



BETTER FRUIT 



Some Facts About Dry Lime Sulphur 



By A. J. Gunderson. Horticulturist for Sherwin-Williams Company 



WITHIN recent years the Sherwin- 

 Williams Company has placed on 

 the market a new spray product known 

 as Dry Lime Sulfur. This has been 

 brought about by a process of stabiliz- 

 ing 33° Baume lime sulphur solution by 

 the addition of a stabilizing substance 

 such as a carbohydrate or a sugar fol- 

 lowed by a special process of drying. 

 Orchardists and experiment stations 

 have obtained excellent results with 

 dry lime sulphur even when used in 

 lesser amounts than would have been 

 thought necessary when judged from 

 the experience had with ordinary lime 

 sulphur solution. 



While this fact has proven of great 

 interest to all orchardists and experi- 

 ment stations it has been very discon- 

 certing to a few critics who like to be- 

 lieve that since sulphur, chemically 

 speaking is always sulphur, it is im- 

 possible for the sulphur in Sherwin- 

 Williams' dry lime sulphur to be more 

 efTicient per unit of sulphur than the 

 sulphur in old-fashioned lime sulphur 

 solution. With equal assurance one 

 might assert that carbon is always car- 

 bon and that willow charcoal, graphite 

 and the diamond are equally efficient 

 and yet we know that the diamond is 

 worthless for kindling a fire and for 

 writing on paper or as a component of 

 gunpowder; likewise, willow charcoal 

 is not a brilliant, sparkling gem in de- 

 mand by jewelers nor can it be used to 

 cut glass. 



It has been definitely established that 

 lime sulphur solution must be used at 

 the rate of from one gallon to eight 

 gallons in order to kill San Jose scale. 

 Every fifty gallons of diluted spray 

 therefore will contain approximately 

 five and one-half gallons of lime sul- 

 phur solution, or a total of approxi- 

 mately fourteen pounds of sulphur in 

 solution. On the other hand the results 

 of experiments conducted in orchards 

 infested with San Jose scale have 

 shown that dry lime sulphur controlled 

 San Jose scale just as effectively at 

 strengths recommended by the Sher- 

 win-Williams Company although con- 

 taining considerably less amounts of 

 sulphur in solution. Certain experi- 

 ments conducted in the states of Wash- 

 ington and Illinois in the spring of 1919 

 have further confirmed such recom- 

 mendations and in certain cases dry 

 lime sulphur proved even more effect- 

 ive in the control of San Jose scale than 

 lime sulphur solution. 



Experiments conducted in certain 

 other states have shown definitely that 

 dry lime sulphur controlled apple scab 

 and peach leaf curl just as effectively 

 as lime sulphur solution. Furthermore 

 it has been demonstrated that dry lime 

 sulphur used in combination with ar- 

 senate of lead did not cause foliage in- 

 jury and incidentally stimulated an un- 

 usual finish and color on red varieties 

 of apples. 



The explanation recognized by ento- 

 mologists of this country as to how lime 

 sulphur kills San Jose scale is that sul- 

 phur combined with calcium to form 



polysulfides of calcium oxidizes after 

 having been applied to the infested 

 trees and that oxygen is removed from 

 the scale, resulting in its chemical suffo- 

 cation. It is very probable that ento- 

 mologists have overlooked the fact that 

 sulphuretted hydrogen or hydrogen sul- 

 fide is extremely toxic to both insect 

 and plant life and that it plays an im- 

 portant role in sulphur insecticides. 



Sulphuretted hydrogen is a gas which 

 is not generally available commercially 

 and if it were available it could not be 

 applied easily and directly in such a 

 manner as to kill the insect and not in- 

 jure the tree. The most satisfactory 

 method of applying sulphuretted hy- 

 drogen is the indirect one of using cal- 

 cium polysulphide or so-called lime sul- 

 phur. 



Lime sulphur solution is a water so- 

 lution of a compound of calcium and 

 sulphur known to the chemist as cal- 

 cium polysulphide, together with lesser 

 quantities of compounds of calcium 

 sulphur and oxygen such as calcium 

 thiosulphate, etc. This lime sulphur 

 solution when diluted and used as a 

 spray on scaley trees decomposes in 

 the presence of carbonic acid yielding 

 sulphur, hydrogen sulphide and calcium 

 carbonate. Subsequently other reac- 

 tions take place in which the sulphur, 

 calcium thiosulphate and other sulphur 

 compounds participate. If there is any 

 difference in the toxic effect of a unit 

 of sulphur in dry and liquid lime sul- 

 phur there must be reasons for that dif- 

 ference. Possibly we may never know 

 all of the reasons, but we believe the 

 phenomena may be explained in part as 

 follows: 



We believe that the spray made from 

 dry lime sulphur has greater wetting 

 and spreading and penetrating power. 

 The film resulting from a spray of dry 

 lime sulphur is less permeable to de- 

 composing gases and vapors; and al- 

 though more tenuous is more integral 

 and coherent. The film resulting from 

 a spray of dry lime sulphur dissolves 

 anr retains the liberated sulphuretted 

 hydrogen for a longer time. The film 

 directly in contact with the scale insect 

 is decomposed by the carbonic acid and 

 other organic acids produced by the 

 transpiration of the insect perhaps to 

 even a greater extent than by the car- 

 bonic acid of the air. Owing to the 

 lesser permeability of the film from dry 

 lime sulphur there is a greater concen- 

 tration of the toxic vapors for the same 

 length of time or an equal concentra- 

 tion for a greater length of time per 

 unit of sulphur as compared with the 

 film of ordinary lime sulphur solution. 

 In other words, when dry lime sulphur 

 is used a larger percentage of the sul- 

 phur content goes into the insect and 

 less to the atmosphere than is the case 

 when lime sulphur solution is used. 



It is possible that the toxicity of the 

 sulphur liberated from dry lime sul- 

 phur is somewhat greater than that lib- 

 erated from ordinary lime sulphur solu- 

 tion for the reason that the former is 

 in a state of extreme division, almost 



April, ipso 



colloidal in fact, and the stabilizer re- 

 tains it as if it were in a sort of a gel. 



Orchardists are interested more spe- 

 cially in what dry lime sulphur will 

 accomplish under actual orchard condi- 

 tions. In view of the fact that dry lime 

 sulphur will give just as good results 

 as lime sulphur solution in the same 

 orchard, we believe that the explana- 

 tion just given is a sound and satisfac- 

 tory one. 



The Sherwin-Williams Company has 

 based its recommendations for the use 

 of dry lime sulphur upon the results of 

 careful orchard tests and further sub- 

 stantiates its claims for this product 

 upon the fact that thousands of fruit 

 growers are using dry lime sulphur 

 with most excellent results. Dry lime 

 sulphur will not only control effectively 

 the insects and fungous diseases for 

 which it is recommended but, further- 

 more, eliminates all of the objectionable 

 features connected with lime sulphur 

 solution. These include loss due to 

 leakage, freezing, crystallization and 

 great weight in handling. Orchardists 

 everywhere are familiar with these ob- 

 jectionable features. 



Dry lime sulphur is rapidly becoming 

 a standard spray material and it is our 

 prediction that it will entirely supplant 

 lime sulphur solution in two or three 

 years. 



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