190 SCIENCE AND FRUIT GROWING 



spraying 52 per cent, of the total copper which had been 

 applied and 0^005 grams per kilo where there had been seven 

 sprayings, this quantity representing 19 per cent, of the total 

 applied in that case. But the copper was in a very insoluble 

 form, no doubt in the form of carbonate, for both these samples 

 on treatment with ordinary distilled water yielded a solution 

 containing only i part in 2,000,000. This, indeed, is stronger 

 than a solution which has been found to be appreciably injurious 

 in water- cultures (i in 5,000,000), but plants are, no doubt, much 

 more sensitive to deleterious agents when they are growing 

 under the abnormal conditions of water- culture, than when 

 growing under natural conditions in the soil. At the same time, 

 however, it must be remembered that soil-gases and soil-water 

 may contain much carbon dioxide, and the presence of this would 

 materially increase the amount of copper dissolved; hence, as a 

 precaution, it is well to reduce the amount of copper applied in 

 spraying as far as possible, and as far as is consistent with there 

 being no reduction in the fungicidal effect. 



Copper Injury 



As has been pointed out, since a fungus and its host plant 

 are both organisms built up of vegetable cells, it is impossible 

 to kill the one without running the risk of injuring the other. 

 The scorching of the leaves of the tree is generally a necessary 

 accompaniment of fungicidal action. Much misunderstanding 

 on this point exists in this country, growers imagining that 

 scorching by fungicides is evidence that the spray-fluid has not 

 been properly made. 



A considerable amount of work has been done on Bordeaux 

 injury, especially in America, and valuable information on the 

 subject will be found in a Bulletin of 1907 by U. P. Hedrick. 1 

 Besides references to previous work, this Bulletin contains the 

 results of experiments made at the station in 1906, and of reports 

 received from 108 growers as regards their experiences in 1905. 

 On all essential points the experiments and the reports are in 

 satisfactory agreement. 



The nature of the injury inflicted by Bordeaux mixture con- 

 sists in a destruction of the cells of the plant. In the case of 

 the leaves, this causes brown patches to appear, similar to those 

 produced by various diseases, and by frost ; often the whole leaf 

 turns yellow, and partial or entire defoliation may occur. In 

 the case of the fruits, a similar spotting or russeting is produced, 

 1 No. 287 of the Geneva (New York) Station. 



