PLA'S'T DISEASES AND INSECT PESTS 



159 



Apple scab is a fungous disease which attacks the blossoms 

 and other parts of the tree, finally manifesting its effect on 

 the fruit, which becomes scabby and shriveled and drops. 

 Extensive losses are suffered in this way. The disease is 

 thought to be more prevalent in wet seasons. The remedy 

 is to spray with Bordeaux mixture once before blossoming. 



Figure 70. — Spraying fruit trees. 



immediately after the petals fall and again in a few days. 



Formula for Bordeaux Mixture 



Copper sulphate (blue vitriol), 5 lbs. 



Quicklime (not slaked), 5 lbs. 



Water, 50 gallons. 



Dissolve the copper sulphate in 25 or 35 gallons of water. Slake 

 the lime in the remaining part of the water, and mix. To this amount 

 of Bordeaux mixture }4 lb. of Paris green may be added to form a 

 general insecticide to be used on fruit- bearing bushes and trees. 



Scab and scale diseases may be similarly treated with 

 the lime-sulphur solution. To control the codhng-moth, 

 there should be a midsummer spraying with two pounds of 

 arsenate of lead to fifty gallons of water. 

 Questions: 



1. What can you say of the nature of plant diseases? 



2. Ijeam to write down, without looking, the names of the 

 diseases discussed in this lesson and the plants they attack. 



