CHAPTER XL. 



FUNGOUS AND PHYSIOLOGICAL DISEASES. 



While the number of diseases affecting cirtus fruits 

 is not nearly so large as that affecting many other groups 

 of fruits, still they are of sufficient importance to attract 

 serious attention. As a general thing they can be suc- 

 cessfully combated by means at the disposal of every 

 grower. Some, however, are due to negligence or mal- 

 treatment. Others of these diseases are intimately asso- 

 ciated with the methods of cultivation and fertilization, 

 but they may appear in groves where the best and most 

 intelligent care is given. 



Many of the diseases are due to the attacks of fungi. 

 These attack different parts of the plants the roots, 

 stems, branches or leaves and interfere with their func- 

 tions, eventually bringing about the death of the part 

 attacked and, in some cases, the whole tree succumbs. 

 These fungi are spread by means of spores which bear the 

 same relation to the fungus as seed does to the higher 

 plants. The spores are scattered by the wind or rain 

 and under favorable conditions of heat and moisture, 

 grow and enter the tissues of the plant. Slender fungal 

 threads, the mycelium, grow about in the tissues until 

 they have obtained food enough and have grown suffi- 

 ciently to produce spores again. These are again scat- 

 tered, and so the life circle is completed. In the follow- 

 ing pages diseases of this nature are placed under the 

 heading of Fungous Diseases. 



There is another class of disease which attack citrus 

 and other trees or plants. These are intimately associ- 



