September. 1921 



SCIENTIFIC AGRICULTURE 



11 



Althougli tliese determiiiatious are not 

 sufficiently exliaustive to make observa- 

 tions in detail on fh^i compara)tive adhe- 

 rence of spray and dust, yet they are 

 sufficient to establish certain points. It 

 Avill be noticed that the actual amounts 

 of copper and arsenic used pier acre in 

 each application, Avere greater in the 

 spray than in the dust. Nevertheless the 

 amount dietected immediately after appli- 

 cation were but little gTeate.r on the 

 sprayed foliage than on the dusted. It 

 is obvious that the wastage of material 

 in the process of application is no grtjater 

 in dusting than in spraying. In fact ac- 

 cording to the figures given, spraying is 

 a trifle the more wasiteful. 



A perusal of the determination reveals 

 thb. fact that the sprayed material has a 

 greater power of adherence than the dust- 

 ed. In all cases the amounts of copper 

 and arsenic on the dusted foliage d'ecreas- 

 ed more rapidly with the lapse of time than 

 the copper and arsenic on the sprayed 

 foliage. This must be rfegarded as a defect 

 in the dust, a defect which will have to be 

 remedied by a close observation of the 

 foliage, and by the application of an addi- 

 'tioiial dust following hieavy rains if cir- 

 cumstances seem to warrant it. Under 

 Nova Scotia conditions in th© orchard, it 

 is not usual to expect a fungicide-insec- 

 ticide to function more than tAvelve days 

 on account of the neied of fresh applica- 

 tions to cover new growth. For this per- 

 iod of time the dust will usually be effec- 

 tive. 



Material. 



3-1 dust 



3-1 dust 



3-1 dust 



3-1 dust 



3-1 dust 



2-10-20 Bord-calcium arsenate spray . . 



do. do. 



do. do. 



do. do. 



do. do. 

 3-1 dust and 90-10 sulphur-lead ar- 

 senate dust 



2-10-40 Bord-calcium arsjenate spray, 

 and 1.40 soluble sulphur-calcium ar- 

 senate-lime spray 



Physiological Effect on Fruit and Foliage. 



On tlie foliage of thjei apple no purely 

 physiological effects, either beneficial or 

 detrimental, have been observed from the 

 use of dust of the formula given in this 

 article. To determine the limits of safety 

 of the dust, a series of experiments were 

 conducted during the past three seasons. 

 Small orchard plots were treated with, 

 dusts of the following formulae : — 



1. 0%Cu — l%As. 



2. l%Cu — l%As. 



3. 2% Cu — 1% As. 



4. 3% Cu — 1% As. 



5. 4% Cu — 1% As. 



6. 0% Cu — 1% As. 



7. 6%Cu — l%As. 



8. 7%Cu— l%As. 



9. 8% Cu — 1% As. 



10. 10%Cu — l%As. 



11. 2i/2%Cu — 0% As. 



12. 21/2% Cu — 1% As. 



13. 21/2% Cu — 2% As. 

 14 21/2% Cu — 3% As. 

 15. 21/2% Cu — 4% As. 



On all these plots no foliage injury that 

 would be noticed by a casual observer was 

 apparent. However, the foliage of plots 

 9 and 10, and to a very small extent that 

 of plot 8, was more or less mottled with 

 the minute purple spots typical of inci- 

 pient copper injury. No arsenic injury^ 

 was apparent on any plot. It is evident 

 from the foregoing tliat dusts of the 

 formulae proposed are absolutely harm- 

 less to foliage. 



Applications made P.C. of apples 



russetted. 



Semi-dormant only 0. 



Pink application only 7.6 



Calyx application only 12.7 



Ten day applicatioii only .... 0. 



All four applicaitioms 14.2 



Sieimi-dormant only . . 0. 



Pink application only 10.9 



Calyx application only 20.8 



Ten day application only . . . . 0.6 



All four applications 28.2 



All four applications, tlie 90-10 

 being used for calyx appli- 

 cation only 5.8 



All four applications tlhe soluble ^ 

 sulphur spray being used for 

 calyx application only " 10.5 



