1891.] ESSAYS. 83 



I am confident that the reason why the use of Paris green has 

 been so unsuccessful in many cases for the destruction of insect 

 h'fe is from the fact that we have been unable to use it in a form 

 concentrated enough to reach all parts of the plant without 

 injury. This will also apply, in a measure, to the fungicides. 



For the purpose of destroying both insects and fungous 

 pests, we must make an application of simple solution of sul- 

 phate of copper, called by the French eau cdeste, to the twigs 

 and branches before the leaves appear to destroy any germs of 

 the scab that may be lodged in the crevices of the bark ; then 

 as soon as the leaves have unfolded the lime and Paris green 

 mixture must be applied for the tent caterpillar and the canker 

 worm. Then as soon as the petals have fallen, a second 

 application should be made for the codling moth and plum 

 curculio. 



This application must be repeated at the proper intervals of 

 from one week to twenty days, according to the weather, until 

 July 1. After this, the Paris green not being needed, the am- 

 moniacal carbonate of copper may be used. The latter appli- 

 cation is to be preferred, from the fact that it does not disfigure 

 the fruit, while if the Bordeaux mixture is used late in the season 

 it adheres to the fruit in such a manner as to injure its sale 

 unless washed. 



No substance has been found that can be used in this way, 

 and at the same time, as the above fungicides and insecticides, 

 owing to the apple maggot, a little insect that is doing, in many 

 localities and upon some varieties, more injury even than the 

 codling moth. The destruction of the fruit before the maggot 

 escapes is the only remedy yet suggested that promises to be of 

 any value. 



The Pear. The insects attacking the pear that can be de- 

 stroyed by arsenites are the codling moth and the plum curculio. 

 The fungi that can be killed by copper solutions are the pear 

 leaf blight and the pear scab or pear fusicladium. 



The pear leaf blight is another minute parasite plant some- 

 what like the apple scab, but perhaps working deeper into the 

 tissues of the leaf, causing all the leaves often to drop from the 

 tree, and which also causes the scab and cracking of the fruit so 



