PLANTS IXJURED. 



159 



Injury to Plants caused by Spraying, 

 The strong prejudice against the use of Paris green for 

 spraying which was met with in Medford in 1891 was partly 

 caused by the belief that both trees and garden plants would 

 be injured or killed thereby. This belief was shared by many 

 people and was largely based upon the results of the work 

 of the first commission, as observed in 1890. Many indi- 

 riduals who had experimented with London purple and Paris 

 green in an attempt to protect their trees had succeeded 

 only in destroying the foliage. It is true that the foliage 

 of many trees was injured in 1890, and that to a less extent 

 this occurred in the work of 1891. Yet much of the appar- 

 ent injury was effected by other causes than spraying. Ln 

 the investigation of complaints that the foliage of trees had 

 been burned, it was found that in some cases the injured 

 trees had not been sprayed. In at least one case the sup- 

 posed burning was caused by the effect of a late frost. A 

 blight upon fruit trees early in the season closely resembled, 

 upon superficial examination, the appearance produced by 

 arsenical burning. Later in the season, during the drier 

 portion of the summer, many leaves on trees, which had 

 not been sprayed, turned yellow and fell, presenting much 

 the same appearance as was observed on foMage which had 

 been burned by spraying. Many reports were received that 

 trees had been killed by spraying, but in most of these cases 

 it was not clearly proved that death was not due to some 

 other cause. Still there is evidence that some young trees 

 were either killed by spraying or were so weakened by 

 burning or defoliation resulting from spraying that they 

 succumbed to the heat of the summer. Such a result is un- 

 usual, however. An apple tree which was sprayed in 1890 

 with the contents of fifteen tanks of the Paris green mixture, 

 each tank containing a pound of Paris green, was not per- 

 manently injured. It is said that many young and tender 

 plants in gardens were not only seriously injured but actually 

 killed by spraying ; yet where this happened it was prob- 

 ably due to some ignorance or carelessness in the use of the 

 insecticide. Some species of trees a-re more susceptible than 

 others to the efiects of the poison. The foliage of plum 



