364 Diseases of Truck Crops 



by any spray. Fungicides are helpful only in pre- 

 venting entrance of the parasite in the host. They 

 are as ineffective in controlling insect pests, as are 

 insecticides in controlling fungous diseases. 



(a) Bordeaux Mixtures. This is the standard 

 fungicide. The strength used for tender plants is 

 three pounds of copper sulphate also known as blue 

 stone, six pounds of lime, and fifty gallons of water. 

 The easiest way to prepare it is to dissolve the blue 

 stone thoroughly in twenty-five gallons of water. 

 The best quality of unslaked lime should be used 

 and slaked in a little hot water, care being taken, 

 however, not to flood it while slaking, nor to let it 

 become too dry. When the slaking is completed, 

 enough water is added to make twenty-five gallons. 

 The limewater and the blue stone solution are 

 then mixed, pouring first one part of lime water, then 

 another part of the blue stone; the mixture is then 

 strained and used at once. With crops with delicate 

 foliage, such as watermelon, weak Bordeaux must be 

 used to prevent burning of foliage (see page 243). 



For truck crops with less delicate foliage, the stand- 

 ard Bordeaux mixture is 4-4-50 that is, four pounds 

 copper sulphate, four pounds unslaked lime, and 

 fifty gallons of water. 



Stock Solutions. In spraying large areas, it is not 

 always practical to weigh out and prepare the in- 

 gredients at short notice. The trucker will therefore 

 find it advantageous to prepare stock solutions so 

 that large quantities of both dissolved copper sul- 



