90 CONTROLLING INSECTS AND DISEASES 



before it enters the tissue of the host. To be effective, the spraying 

 material must be appUed to the host plant before the spores of 

 the fungus germinate. Therefore, if the spraying is to be most 

 effective, an attack of the fungi must be anticipated, and the 

 spray applied before the disease appears. In localities where given 

 diseases are prevalent, the usual time of attack must be known 

 and precautionary measures taken accordingly. Some diseases 

 are almost continuous in their attack through a large part of the 

 growing season. Such diseases can be controlled only by repeated 

 applications of spraying materials, so that the new foliage that 

 develops between applications will not remain long without pro- 

 tection, and the coating will be renewed on older foliage from which 

 it has been washed by rains, or more or less dislodged by reason 

 of foliage expansion. 



The spraying material best adapted to the control of fungous 

 diseases on vegetable crops is known as Bordeaux mixture. 



FORMULAS FOR SPRAY MIXTURES 



Bordeaux mixture consists of lime, copper sulfate and water. 

 The Ume is slaked with water and the copper sulfate dissolved 

 in water. The two ingredients are kept separate until immediately 

 before the spraying is to be done; then they are each diluted to 

 half the volume of the spray mixture desired, poured together 

 and stirred thoroughly. 



In slaking the lime only a small quantity of water should be 

 applied at first, and additional amounts added from time to time 

 as the slaking proceeds, only enough water being supplied each 

 time to keep the mass from becoming overheated. After slaking 

 is completed, the mass may be diluted to any desired volume. 

 Before it is combined with the copper sulfate the lime must be 

 strained to remove any coarse particles. 



To dissolve the copper sulfate, it should be suspended in a 

 sack or basket near the top of a barrel or other wooden receptacle 

 filled with water. If thrown into the bottom of the barrel and 

 covered with water, the copper sulfate crystals will soon become 

 surrounded by a saturated solution of copper sulfate, which will 

 prevent any further dissolving of the crystals. On the other hand, 

 if the crystals are suspended as directed, the solution of copper 

 sulfate, which is heavier than water, will sink towards the bottom 

 of the barrel as fast as it is made, and leave the purest water in 

 contact with the crystals to continue the dissolving process. 



