42 PROTECTION" OF PLAXTS, 1916-17 



WHAT INSECTICIDES AND FUNGICIDES SHALL WE USE IN 

 1917, AND WHEN SHALL WILL SPRAY THIS YEAR? 



Father Leopold, Oka Agricultural Institute. 



Spraying operations, to my mind, are among the most important opera- 

 tions in the orchard, and it seems to me that the further we go the more we 

 ha^'e to learn about the whole gamut of these operations. Some years ago 

 we left out Bordeaux mixture, more or less, to take up Lime Sulphur Wash ; 

 we found that Paris Green was not so good as Arsenate of Lead. Then we 

 used paste Arsenate of Lead and we are beginning to replace it by the 

 powder, and now, I am asking myself if we cannot find a cheaper and just 

 as effective an insecticide as arsenate of lead. I am also convinced that we 

 can omit without loss the dormant spray and yet get a good crop of Fameuse 

 and Mcintosh apples withoutapple scab. 



I am offering here for your consideration and discussion a few important 

 items in spraying that may mean a saving this year either in the crop itself 

 or in the buying of the necessary quantity of insecticide for the fruit grower. 



The first point I wish to mention is that according to the results and 

 experiences in Nova Scotia of Mr. G. E. Sanders, the Field Officer in charge 

 of the Dominion Entomological Laboratory at Annapolis Royal, perhaps we 

 should substitute arsenate of lime for arsenate of lead in all lime and sulphur 

 sprays and with Bordeaux mixture. 



In regard to substituting arsenate of lime for arsenate of lead, I may 

 state that arsenic, in the form of arsenate of lime, will cost less than 55% 

 of what arsenic will cost in the form of arsenate of lead. 



Arsenate of lime does less damage than arsenate of lead with an equal 

 strength of lime sulphur. When we add arsenate of lead to lime sulphur 

 solution a chemical change takes place resulting in the formation of lead 

 sulphide and three kinds of arsenate of lime, one of them, mono-calcic- 

 arsenate, is entirely soluble and is the cause of a large part of the burning 

 which comes from the use of lead arsenate and lime sulphur together. 

 When arsenate of lime is added to lime sulphur no chemical change takes 

 place and so no soluble arsenic is formed. Therefore arsenate of lime is safer 

 than arsenate of lead with lime sulphur wash. 



Moreover, arsenate of lime causes less waste when it is added to lime 

 sulphur solution than does arsenate of lead. When arsenate of lime is 

 added no chemical change takes place, but when arsenate of lead is added 

 nearly all the lead goes to the bottom of the tank as lead sulphide precipitate 

 or sludge. Thus 35% of the sulphur is lost from the solution and it is on 



