PLANT DISEASES 



241 



dipping into it any bright piece of steel. If it has a coating of 

 copper upon it when withdrawn, more lime should be added. 

 Another test is to put a few drops of potassium ferrocyanide 

 into a little of the solution. If it turns brick red, more lime 

 is needed. If the potassium ferrocyanide remains yellow, suffi- 

 cient lime is present. An excess of lime does no harm. The 

 mixture here described is often known as the 5-5-50 solution, 

 the numbers referring to the quantity of each ingredient 

 employed. Other 

 proportions may 

 be taken : the 

 4-4-50 and the 

 3-3-50 are pop- 

 ular. The mix- 

 ture should be 

 strained before 

 using. This spray 

 does not poison 

 insects, and if a 

 poison is desired 

 with it, arsenate 

 of lead in the pro- 

 portion of two 

 or three pounds 

 to fifty gallons may be added. Copper sulphate is often used 

 alone with water in the proportion of one pound to twenty 

 gallons. This can be used only before the buds open, never 

 on the leaves. 



Lime-sulphur wash. For spraying all woody plants in 

 the dormant condition, the lime-sulphur wash is preferred. 

 It consists of fifteen pounds each of lime and sulphur and 

 fifty gallons of water. To make it, bring the water to the 

 boiling point and add the lime. Make a paste with the sul- 

 phur and a small quantity of hot water, add to the boiling 



Photograph by Bateman Manufacturing Co. 



FIG. 178. Spraying a young fruit tree by means of a 

 bucket pump sprayer 



