INSECTS OF THE CITRUS FRUITS 301 



Fumigation is practised by covering the tree with a tent 

 made of hea^'y duck. Under the tent the fumigating material 

 is placed. Hydrocyanic acid gas is the material commonly 

 used, and is made by depositing sodium or potassium cyanide 

 in an earthen jar and covering it with sulphuric acid. The 

 jars should be at least 2 gallons in capacity, to prevent the 

 acid from foaming up and spilling out. The amount of 

 material which is used depends upon the size of the tree and 

 the insect which is doing the damage. There are dosage 

 tables worked out by the United States Department of 

 Agriculture and the various State experiment stations, and 

 these should be consulted for a more detailed study of 

 fumigation. 



The fumigation gi\'es better results and produces less 

 injury to the foliage if it is done at night instead of in the 

 daytime . 



The season of the year at which fumigating is done depends 

 upon the life history of the insects and the condition of the 

 tree. The fumigation should be carried on when the insects 

 are in the most tender stage and can be easily killed, and 

 the time will vary slightly for each insect. However, from 

 August to January seems to be the time which gives the 

 most satisfactory results. 



The dosages as well as the length of time vnry with the 

 different scale insects. This phase can be learned in some 

 more complete treatise on the subject. 



REVIEW QUESTIONS. 



1. Name the fruits included in the citrus class. 



2. Why is the citrus industry confined to certain special districts? 



3. How does the grape fruit differ from, the orange? 



4. Discuss the propagation of the citrus fruit. What form of budding is 

 used? 



.5. What is the best type of soil for the citrus fruit? How does the sub- 

 soil regulate the value of the top soil? 



6. Why is good cultivation essential? 



7. How should a citrus orchard be planted? 



8. Discuss the curing of citrus fruits. How does the curing of the 

 orange differ from that of the lemon? 



9. What method of picking is used for the lemon? Why? 



10. How does the picking of the orange differ from that of the lemon? 



