SCIENTIFIC AGRICULTURE 



September, 1921 



safety on foliage. During 1918 the total 

 amount used did not exceed half a ton. 

 This was used for the most part by the 

 writers, but C. E. Peteh and several other 

 officers of the Entomological Branch nsed 

 a certain amount as also did Prof. W. H. 

 Brittain. of tlie Nova Scotia College of 

 Agriculture. In 1919 eight commercial 

 apple growers in the Annapolis Valley 

 gave the material a thorough test, the 

 aiuount u.si;d by them aggregating be- 

 tween ten and twelve tons, and in addi- 

 tion much material was used in experi- 

 mental work both in Nova Scotia and 

 elsewhere. Tntil this time the material 

 could be considered as being in a purely 

 experimental stage, but in consequence of 

 the satisfactory results obtained and the 

 obvious economics of this method of dis- 

 ease control, there was erieated a very 

 considerable demand for the dust in 1920, 

 tlie consumption («f niaterial in Nova 

 Scotia being about three hundred tons. 

 At the time of writing it would appear 

 that this year (1921) about seven hundred 

 tons Avill be used, and in addition very 

 considerable quantities* are b;ing ai)plied 

 at many various point.s throughout Amer- 

 ica. 



Tile writers have, this season, definite 

 records of the importation into the Anna- 

 polis Valley of Nova Scotia of sufficient 

 raatei-ial to treat four times 13,000 acres 

 of mature ai)ple orchard with some form 

 of fungicide-insecticide combination. How- 

 ever, much orchard treated is young. Also 

 some persons u.se le.ss material than recom- 

 mended, and also a considerable amount 

 of material enters the valley of which 

 no record is obtained. Consequently it 

 i.s estimated that aproximatiily 20.000 

 acres of apple orchard ai'^e being at present 

 dusted or sprayed. In round numbers this 

 area is divided as follows: — 



S,;")00 acres treat' il with spray (mostly 

 liordeaux mixture). 



l.-")00 acres treated witii sulphur-lead 

 arsenate dust. 



10,000 acres ti-eated with copi)er-arsenic 

 dnst. 



^luch of thi? sulpluii--lead arsenate dust 

 is used in conjunction with the coj)per- 

 ar.senic dust as described later. It is ap- 

 parent from the above figures that tlie 

 dust is commerciallx- established. 



Composition of the Dust. 



The fungicidal principle of the dust is 

 dehydrated copper sulphate. During the 

 early experiments the material mostly 

 nsed was the anhydrous salt Cu SO^, but 

 later the copper sulphate mono-hydrate 

 Cu SO^.H^.O has been generally utilized. 

 The first material is white in color, and 

 the lattier a very light shade of blue. It 

 is smooth to the touch and of such a fine- 

 ness that it will pa.ss through a two hun- 

 dred mesh to the inch screen. The in- 

 secticidal ingredient generally nsiid is cal- 

 cium arsenate, although there have been 

 used many other ar.senieals with perfect 

 satisfaction. Taking all the factors con- 

 cerned into consideration, however, such 

 as the ability to form a good dust cloud, 

 power of adherence, safety to foliage and 

 cost, calcium arsenate is the most satis- 

 factory as far as present knoAvledge goes. 

 The main bulk of the material is hydrated 

 lime of the ordinar\' brand. 



Copper-ar.s^enic dusts differing consider- 

 ably from the above, both as to composi- 

 tion and source of material are being used 

 extensively by the officers of th'^ Ento- 

 mological laboratorv at Annapolis Ro.val. 

 and it is not improbable that as a result 

 of work at present mider way. the ma- 

 terials and method of making may be 

 matei-iall.v. altered. 



The ingredients have been used experi- 

 mentiiUy in various proportions, for par- 

 ticularly during the early, experiments it 

 was a matter of considerable speculation 

 as to the relative amounts of each that 

 Avould be desirable. In compounding the 

 dust it was the original idea to make it 

 of such a constitution that the same 

 amount of copper and arsenic would 

 be applied to the foliage of tliei plant un- 

 der treatment, as would under normal cm-- 

 cumstanees be applied by treatment with 

 a standard Bordeaux mixture (2-10-40 

 for the api)le aiul 4-1-40 for the potato). 

 01)viously to get such a result several 

 factors had to l>e taken into consideration, 

 the most prominent being the rate of ap- 

 plication, and the relativie amounts which 

 adhere to the foliage and the amounts 

 which were wasted and went on the 

 ground. Several trials and considerable ex- 

 l>erience were necessary before these fac- 

 tors could be determiiu'd Avithin reason- 



