486 



CITRUS FRUITS AND THEIR CULTURE. 



access of light and upon the action of light, the assimila- 

 tion of food depends. 



Treatment. Spray the 

 leaves with formula (1), 

 and either apply to the 

 trunks as a spray or ap- 

 ply with a stiff brush and 

 scrub them clean. Scrub Fig - 107 - Tree scraper. 



trunks and limbs with soap suds. A tree scraper may 

 frequently be used to advantage. 



PHYSIOLOGICAL DISEASES. 



Die-Back. This disease takes its name from the fact 

 that the young twigs and branches of affected trees die 



back to a distance of 

 from two to eight 

 inches, or even more, 

 from their tips. Sub- 

 sequently the older and 

 larger limbs and 

 branches are affected, 

 unless the disease is 

 checked. 



No citrus trouble is 

 more widely distrib- 

 uted throughout Flor- 

 ida than die-back, and 

 it occurs in California 

 and other citrus dis- 

 tricts as well. No lo- 

 cality is exempt from 

 it and no variety free 



Fig-. 108. Oran f ge_tree Rowing effects from its attack. Trees, 



