CHAPTER XIV. 

 Diseases of Orange Trees. 



Orange trees in California enjoy an enviable reputation for 

 healthfulness. Perhaps in no other part of the world does the 

 citrus family enjoy immunity from disease to such an extent as 

 in our own beloved and golden country. The orange groves of 

 many portions of the world have suffered from what is known 

 as "die back," the new growth of the season dying back to the 

 old wood. It is thought that this disease is occasioned by the 

 roots coming in contact with the hard-pan, which they cannot 

 penetrate. We have had nothing of the kind in this country up 

 to the present time. The only disease for which we have reason 

 to seek a remedy is what is known as the "gum disease." Trees 

 affected with this disease are known at a glance by a general 

 sickly appearance; the leaves grow yellow gradually. The 

 leaves drop off in the extreme stage of the disease, leaving on 

 the leafless tree the fruit, which never attains perfection. The 

 trees die and dry up soon after the leaves fall. The disease 

 commences at the surface of the ground ; the bark rots away, 

 and from the affected parts the sap exudes in the form of a 

 gum. This disease extends until it encircles the entire trunk, 

 usually extending from two to six inches up the trunk, and 

 downwards to the roots and along them, oftentimes to their ex- 

 tremities, rotting the bark on them, thus cutting off all con- 

 nection between the soil and the tree. 



Excessive irrigation and poor or slovenly cultivation are admit- 

 ted by all to be the cause of this dreaded disease. A committee 

 appointed by the Southern California Horticultural Society was 

 instructed to visit the orange groves of Southern California, one 

 of their objects being to ascertain the cause of this gum disease 

 and the remedy for it. This commiUee visited all the principal 



