PROCEEDINGS, 1916. 



41 



No. of Apples Matured per pair of Wagner Trees. 



Dilution of Lime Sulphur 



Arsenate of Lime 



122 



126 



125 



152 



56 



44 



36 



Unsprayed trees averaged 277 apples per pair. 



The trees in this experiment were sprayed three times, once before the blossoms 

 opened and twice after the blossoms fell. At 1.006 sp. gr. and weaker, neither of the 

 poisons caused any noticeable injury with lime and sulphur; 1.007 sp. gr. lime and sul- 

 phur with arsenate of lime caused no dropping of the fruit, but the burning of the leaves 

 was somewhat greater than in the weaker strength -. At 1.007 sp. gr. lime sulphur with 

 arsenate of lead not only gave more leaf injury than the same strength with arsen- 

 ate of lime, but it reduced the crop matured to 27 apple; as compared to 152 where 

 arsenate of lime was used. With 1.008 p. gr. lime sulphur and arsenate of lime only 56 

 were matured, but the arsenate of lead, lime sulphur again proved the more dangerous 

 combination, the trees sprayed with it only maturing 33 apples. The trees sprayed 

 with 1.009 sp. gr. lime sulphur and arsenate of lead only matured one apple, while those 

 sprayed with the same strength of lime sulphur and arsenate of lime matured forty-four 

 apples. Where 1.010 sp. gr. lime sulphur and arsenate of lime were used thirty six ap- 

 ples matured, while arsenate of lead with the same strength of lime sulphur allowed only- 

 five apples to mature. These figure show practically, as the work of Tartar and Rob- 

 inson prove theoretically, that arsenate of lime is a much safer poison to use with the 

 ordinary summer strengths of lime sulphur than arsenate of lead. 



EFFECT WHEN USED ALONE. 



Arsenate of lead when used alone is one of the most harmless of poisons in so far as 

 foliage injury is concerned, but when added to lime sulphur it has been shown to be 

 more injurious than arsenate of lime when used with the same fungicide. 



Arsenate of lime when used with lime sulphur has been found less injurious to foli- 

 age than arsenate of lead, but when used alone arsenate of lime will give most severe 

 burning. This burning is accounted for by the chemists as follows: 



Calcium has a greater affinity r or carbon than for arsenic, so that when the carbon 

 dioxide comes in contact with the calcium arsenate the calcium goes to form calcium 

 carbonate on the leaf and free arsenic is liberated in the form of arsenic acid. Where a 

 fungicide is used with arsenate of lime invariably less burning by the arsenates of lime 

 results, the fungicide seems to protect the arsenate of lime combination from the action 

 of carbon dioxide, and so prevents it from causing foliage njury. Where excessively 

 dilute fungicides were used there did not seem, in some cases, to be enough fungicide 

 solution to protect the arsenate of lime. In this connection the results from a number 



