122 The Spraying of Plants. 



danger may be avoided by adding lime to the liquid in which 

 the poison is held, using equal parts of lime and arsenite, as is 

 also done with London purple. Paris green is heavier than the 

 latter, and must be more frequently stirred when in water. 



Paris green possesses some value as a fungicide. This is 

 probably due to the presence of the copper. Although the 

 fungicidal value of the poison is, perhaps, only one-half as great 

 as that of the Bordeaux mixture, its protecting influence is 

 fairly strong, as has been shown by several investigators. It is 

 without doubt the most valuable single remedy that can be 

 used in an orchard, since it checks most insect injuries, and 

 reduces, to a marked degree, the losses occasioned by fungous 

 diseases, although it cannot be considered as a very energetic 

 fungicide. 



Since Paris green contains less soluble arsenic, it can be used 

 with greater freedom than London purple, as there is less danger 

 of injuring the foliage. When the poison first came into use, 

 more of it was applied than was necessary for the destruction of 

 the insects. The amount has been reduced so that, at present, 

 the following may be accepted as a safe and effective mixture 

 for plants when only one or two applications are to be made. 

 The fine-grained powder is to be preferred, as it does not settle 

 so rapidly, and is more evenly distributed : 



Paris green 1 pound. 



Water 150-300 gallons. 



The more concentrated mixtures should be used only upon 

 plants which are not easily injured, as the eggplant and the 

 potato; in other cases, when the insects are destroyed with 

 difficulty, lime should be added, using an amount equal in bulk 

 to that of the poison. It is always safer to make this addition, 

 even when the mixture is more dilute ; the amount of lime used 

 is so small that no clogging of the machinery will result, and 

 there is no danger of injuring the plants. 



The action of lime in overcoming the caustic properties of the 

 compounds of arsenic has suggested the use of the Bordeaux 

 mixture in combination with these poisons, but especially with 

 London purple and with Paris green. These mixtures have 

 now been in use for several years, and they have, almost with- 

 out exception, given excellent results. The value neither of the 



