45 



This disease is due to the partial absence of the green 

 coloring matter, or chlorophyll, in the leaves of the 

 tree, and gives the leaves the appearance of being 

 variegated yellow and green. 



As the disease progresses, the yellowing of the 

 leaves increases, until these turn practically all yellow, 

 the branches die back, and little, if any, fruit is set. 



In his valuable book on "Citrus Fruits," Professor 

 J. B. Ooit, of the California University, mentions that 

 this disease was probably the most serious problem that 

 Calif ornian citrus growers had to face. At the present 

 time the cause of this disease is but imperfectly 

 known, but as many Californian experimenters are 

 now investigating this citrus malady it is to be hoped 

 that a satisfactory solution of this problem will aoon 

 be found. 



The writer has seen trees badly affected on land 

 showing signs of over-irrigation, on land showing 

 traces of alkali trouble, and to a lesser extent in situa- 

 tions where the conditions for citrus culture were 

 apparently ideal. 



That mottled leaf may in some instances be over- 

 come by the application of somewhat heavy dress- 

 ings of organic nitrogenous manures, the writer has 

 proved from his own experience. The trees on a 

 portion of his citrus plantation growing in a deep, 

 red soil, which was but poorly supplied with humus, 

 developed mottled leaf to a considerable extent, -so 

 that their growth became very slow, and no fruit 

 was set. A dressing of stable manure equal to about 

 5 cwt. per tree was spread over the land and ploughed 

 in early in the Spring. Within a few months the 

 trees were showing signs of recovery, and after a year 

 the mottled leaf had practically disappeared ; the 

 trees were making vigorous, healthy growth, and 

 have remained in good condition ever since. 



Growing among the other perfectly healthy trees 

 of the writer's plantation, odd trees here and there 

 developed mottled leaf, although the conditions 



