PROCEEDINGS, 1917 79 



of a hand atomher with lime sulphur 1.01 sp. gr. Where the apples alone were covered 

 with lime sulphur the apples remained on the tree, but where the leaves alone were 

 sprayed, nearly all the fruit dropped. This indicated that the dropping of the fruit was 

 caused by the action of the spraying material on the leaf. 



Soon after this, Mr. S. B. Chute, of Berwick, sent two outfits out to apply lime sul- 

 phur with the new spray guns. One man sprayed on top of the spraying outfit and dir- 

 ected the spray down, but the other worked from the ground directing the spray up 

 through the tree. Shortly after, Mr. Chute noted that the man who sprayed from the 

 top of the spraying outfit had done practically no harm, while the man who had spray- 

 ed from the ground had done a great deal of injury to the leaves. This seemed to show 

 that lime sulphur hadamoreinjuriouseffectontheundersideof theleaf than on the upper 

 surface. We immediately tested this out at the laboratory and found that lime sulphur 

 1.01 sp. gr. when applied to the upper surface of the apple leaf in July would cause no 

 injury, except a slight tipping where the drop that had gathered at the tip of the leaf had 

 wet the under surface. We also found that the same lime sulphur applied under the 

 same conditions to the under side of the leaf, caused very serious leaf injury which was 

 visible a few hours after spraying and which caused dropping of the fruit and total de- 

 foliation within a fortnight. It was noticed that the burning, as far as the eye could 

 see, appeared first, and was always more prominent, on the upper surface of the leaf. 

 Bordeaux mixture and soluble sulphur applied at double the usual strength of sum- 

 mer spray, and under the same conditions as the above to either the upper or lower leaf 

 surface, caused no injury. 



In regard to up and down spraying, W. H. Volck in Bull. 153 of the University of 

 California Agr. Expt. Station on, — "Spraying with Distillates on the Orange and Grape 

 fruit," states, "In all overshot work (spraying) the foliage was very little injured 

 and in all undershot work and normal spraying the injury was very serious." He ex- 

 plains that overshot work means spraying down so as to wet the top side only of the 

 leaf. Undershot means spraying up so as to wet the under side only while normal spray- 

 ing means wetting both sides* 



In Bull. 72, Storrs Agr. Expt. Sta., Storrs, Conn., C. D. Jarvison page 114 states 

 that in using Bordeaux 4-4-50 (wine gal.) on melons, spraying so as to wet both sides of 

 the leaf gave much more foliage injury than where the spray was applied to the under 

 surface of the leaf only. Again he states that "Spraying thoroughly both sides of the 

 leaves, while increasing the injury to the foliage was only slightly more effective in con- 

 trolling the disease than the ordinary method of spraying the upper surface of the leaves 

 only." 



An alcoholic solution of chlorophyll was made from apple leaves, and the action of 

 the various spray materials on it, tested. It was found that the addition of lime and sul- 

 phur to the chlorophyll solution, caused a heavy floculent precipitate to form, that the 

 addition of soluble sulphur caused a very slight turbidity, and that the addition of the 

 liquid from Bordeaux caused a very slight turbidity. In the latter two cases the tur- 

 bidity was no greater than the turbidity produced by allowing the chlorophyll solution 

 to stand for several minutes exposed to the air. From a study of sectioned leaves which 

 had been sprayed on the under side, there appeared much evidence to show that the re- 

 actions observed on the chlorophyll solution were also taking place within the leaf. The 

 chlorophyll in the palisade cells of leaves sprayed with a strong spray of lime sulphur 

 was darker and more opaque than the chlorophyll of normal leaves, and evidently gave 

 to the upper surface of the leaf its burnt appearance. In all the tests made at that 

 time no difference could be detected from the normal, in sections of leaves which had 

 been sprayed with Bordeaux or with soluble sulphur. It would appear then that one of 

 the factors of lime sulphur leaf injury is the absorption of lime sulphur by the under 

 side of the leaf which destroys either permanently or temporarily the chlorophyll with 

 which it comes in contact. It would also appear that the dropping of the apples follow- 



