130 STATE BOARD OF HORTICULTURE. 



amount of nitrates, ammonia salts, etc., will replace this 

 ingredient. The farmer must add soluble iron salts to his 

 land if he desires to obtain a full yield with the least expense. 

 Dr. E. Wolff, the German authority, found that when soluble 

 iron was omitted in certain culture experiments, the young 

 plants became yellow and sickly, but they quickly became 

 green and assumed a luxuriant growth when a small quantity 

 of iron solution was added.' (Griffith on Manures, p. 268, etc.)" 



Gum Disease. There are various 'forms of so-called " gum 

 diseases." One attacks both young and old trees at the crown 

 and roots of the tree, while another appears on the large limbs 

 in the form of a " scab," and another 'on the trunks and main 

 branches. 



The most deadly of these is the " root form," which is preva- 

 lent almost everywhere. This form of the disease is first 

 detected on the trunks of trees close to the ground, and is an 

 exudation of the sap, which breaks through the bark and con- 

 geals in the form of a gum. No citrus tree is free from the 

 disease, and one of the newest facts regarding its appearance 

 is that frequently the finest trees are attacked. It often hap- 

 pens that in making a search for the early development of the 

 disease, no trace of it is observed until exudation has freely 

 commenced. It often happens, too, that in digging away the 

 surface soil around the stem, little more than a black scratch 

 about one to two inches long has been discovered, which when 

 cut open shows the gummy fluid more or less encircling the 

 wood under the bark. 



Remedy for the Gum Disease. The best method of con- 

 trolling this disease is to cut away the bark surrounding the 

 place from whence the gum is oozing, in order to detect the 

 main parts affected. The wood where the gum is oozing is cut 

 out with a chisel and left for a day or so, to determine if all 

 the disease has been removed. If it is not altogether removed, 

 the affected parts soon commence to ooze out gum, when more 

 of the wood is cut until it ceases. Yellow streaks of sour sap 

 are generally seen in the grain of the wood, which are traces of 

 the disease. If the affected parts show no further exudation it 

 is proof that the disease has been removed, and the affected 

 parts so treated are either waxed over or covered with a good 



