SEMITROPICAL FRUITS 169 



all that may be seen. Under these scales are the little 

 animals that are doing the damage by sucking the juices 

 of the plant. Most of the states of the Union have laws 

 forbidding the shipping into the state of nursery stock that 

 is infected with this pest. It spreads very rapidly through 

 an orchard when it is once introduced. The surest way 

 to prevent its spreading is to burn the affected trees. 

 There are other methods of destroying the scale which, if 

 carried out with great care and thoroughness, may kill the 

 scale and prevent its spreading. One of the most success- 

 ful methods is by spraying with the lime and sulphur 

 mixture. 

 Lime and Sulphur Mixture. 



20 pounds lime 



14 pounds sulphur 



40 gallons water 



Boil one hour and apply while still warm. This must 

 be applied before the buds come out in the spring, for it 

 will destroy opened buds and foliage. 



QUESTIONS AND EXERCISES. 



1. What are citrus fruits? Where are they grown? 



2. Why is the lemon grafted on an orange seedling stock? 



3. In selecting a soil for oranges and lemons, what kind 

 must be avoided? 



4. What are the chief insect enemies of citrus trees? 

 How is each controlled? 



5. Tell what you know about the olive tree. 



