143 



than 1880." The disease is widely distributed in Florida and has by 

 no means rua out, but, on the contrary, seems to be gradually spread- 

 ing. It has alio appedredin Louisiana and California, where, in 

 places, it is said to be very destructive. 



The damage caused by foot rot is very great, and without question 

 much more than that caused by any other orange disease. The first 

 season after the trees are attacked they may bear an unusually large 

 crop of fruit, but this is generally the last full crop produced. By the 

 next season the tree is either killed or else so reduced that it cannot 

 support much fruit. Sometimes trees are nearly girdled in the space 

 of a few months. Whole groves have been entirely destroyed in the 

 course of a few years. Briosi describes its effect in Italy and Sicily as 

 being most serious ; he estimates the damage done in Italy from 1862 

 to 1^578 at more than ^2,000,000. In Florida many fine bearing groves 

 have been almost totally destroyed, but the malady does not appear to 

 be so severe here as in some foreign countiies. Tae annual damage it 

 causes in Florida is estimated at about ^100,000. 



Symptoms. — The first symptom of foot rot is au abundant exudation 

 of drops of gum on the trunk of the tree near the base. This occurs 

 over a limited portion of the bark in the first stages of the disease, and 

 may appear in one or several distinct patches. In this stage the bark 

 will be found to be discoloured, having become brownish, and to contain 

 numerous cavities filled with gum. The inner bark becomes watery 

 and more or less rotten, and has a very disagreeable, fetid odour. As 

 the malady develops, the demarcation between the healthy bark and 

 the diseased patches becomes very apparent The plant endeavours to 

 throw off the disease and a separative layer is formed between the 

 healthy and diseased portions. The patch ®f diseased bark thus deli- 

 mited, dries up, the edges break away where the separative layer is 

 formed and gradually curve up in drying. Finally the patches of di- 

 seased bark are thrown off. The death and decay of the tissues caused 

 by the disease extend through the bark and apparently for some dis- 

 tance into the wood. The cambium layer, the most vital part of the 

 tree, situated between the bark and the wood, is destroyed, and when 

 the bark is thrown off there is no possibility of new bark growing over 

 that portion The patches of bark which first become diseased, are ir- 

 regular in shape and vary greatly in size, but are usually from 1 to 4 

 inches in diameter. The exudation of gum occurs principally in the 

 spring or in early autumn, after the rainy season, while delimitation 

 and detachment of the bark usually take place during the summer or 

 winter. 



As the disease progresses, gum exudes on other portions of the bark 

 which are in turn thrown off. It is quite common for a circle of bark 

 surroundings an old diseased spot to become affected and be thrown off, 

 thus enlarging the spot. The malady gradually spreads in all direc- 

 tions, but ; principally down on the main crown roots and around the 

 trunk in a lateral direction. Year after year other portions of bark 

 become affected, until the tree is entirely girdled and thereby killed. 

 In malignant cases the disease runs its course and kills the tree in two 

 years or less, while in mild cases the growth of the tree is scarcely af- 

 fected, and Jin a few years the wounds are often completely covered 

 with the new growth from the sides. The destruction of the bark on. 



