96 



DISEASES OF CROP-PLANTS 



For use as a bark wash the stock solution is diluted at the 

 rate of i gallon to 7-10 gallons of water. Arsenate of lead may 

 be added to lime-sulphur sprays, 1-2 oz. of paste or |-i oz. of 

 powder to the gallon, and increases the fungicidal value as well 

 as acting as a poison for biting insects. Paris green cannot 

 be used with lime-sulphur. 



Lime-sulphur solution has a strong caustic action, and 

 contact with skin or clothes should be avoided. Copper vessels 

 should on no account be used in its preparation or application. 

 This includes copper spraying machines, which suffer rapid 

 deterioration. Tinned or galvanised receptacles may be em- 

 ployed. The spraying outfit should be well washed out after 

 use. 



Self-Boiled Lime-Sulphur. 



This is a rather weak fungicide which is safer than Bordeaux 

 or boiled lime-sulphur on tender leaves or flowers. In its pre- 

 paration the slaking of the lime is used to supply the necessary 

 heat. About 10 lb. of best stone lime is placed in a barrel ; 

 an amount of water nearly sufficient to cover the lime is added, 

 and, as slaking begins, 8 lb. of sulphur, carefully freed from 

 lumps, is well stirred in ; the barrel is then covered to keep in 

 the heat and the mixture allowed to stand with occasional 

 stirring for not more than 10-15 minutes. When the action is 

 judged to be complete more water is added and well stirred, 

 and the quantity of wash brought up to 40 gallons. The mixture 

 should have the coarser particles of lime strained out, but the 

 finer sediment should be well worked through the strainer. As 

 the sediment settles quickly good agitation is needed in the 

 sprayer. The mixture can be used as a basis for an iron sulphide 

 spray (see below). 



Since different limes vary greatly in their heat of slaking 

 exact instructions cannot be given for the time of cooking. 



