POISON SPRAYS 311 



London Purple. — This was once a popular form of poison for 

 use in gardens and orhards. It is now seldom used, as its compo- 

 sition is quite variable, the arsenic content running from 30 to 50 

 per cent. Use it, if at all, a little stronger than you would Paris 

 green. 



Arsenate of Lead. — This form of arsenic is used abundantly on 

 potatoes, orchard trees and for almost all purposes in fighting biting 

 insects. It is not so easily washed off the leaves by rams as are 

 other forms of poison. Its composition is more uniform, and there 

 is a less proportion of free arsenic present to injure the leaves. It is 

 easily combined with the dilute forms of sulfur for summer 

 sprays. It is sold in two forms, either as a thick paste or as 

 a powder. If desired for spraying purposes the paste is to be 

 preferred, as it dissolves more readily. The dust is sometimes 

 used to mix with land plaster or air-slaked lime for dusting such 

 plants as potatoes or low-growing vegetables. This is done in 

 the morning when dew is on the plants. The land plaster helps 

 dilute the arsenate of lead and causes it to cover more plants. It 

 also helps to hold the poison on the plants, as it will harden when 

 wet with the dew and cling, as whitewash does on a board 

 fence. The use of molasses with such poisons causes insects to eac 

 the poisons more readily. 



There are several strengths in which the arsenate of lead may be 

 used, depending upon the insects to be killed, and also depending 

 upon the danger of plants to injury; two pounds paste, or one 

 pound powder in 50 gallons of water or lime-sulfur can be used on 

 the peach against curculio and brown rot. It may be a little stronger 

 for apples. On grapes for grape beetles or root worms and for 

 fighting the rose chafer, four or five pounds may be used to each 

 50 gallons of the liquid. 



Arsenate of lime of good quality is much cheaper than the above 

 and is used in about the same amounts. If used with lime or sprays 

 containing lime, Bordeaux or lime-sulfur, there is little danger of 

 burning leaves. If used alone it may injure leaves somewhat. The 

 powdered form is used for dusting on potatoes, cabbage, cotton, 

 corn, etc., when plants are moist with dew. For the home made 

 paste form see directions under white arsenic, or use two pounds 

 white arsenic and one or two pounds of pure fresh lime (CaO). 

 Boil 40 minutes in a gallon of water. 



Arsenite of Zinc — This was first used in the Pacific states and in 

 the trucking regions of the Atlantic slope. It is a good substitute 

 for arsenate of lead. If used with lime-water or with Bordeaux 



