145 



The manner in which, the disease spreads, appearing at different 

 dates first in one country and then in another, and extending gradu- 

 ally from grove to grove, strongly indicates that it is contagious, being 

 caused or at least greatly aggravated by some parasitic organism. 

 Some investigators also think that the disease is due to physiological 

 derangements, for instance, imperfect aeration of the roots. The most 

 effective treatment known is based largely on this supposition. 



Observation has shown that the disease is most common where any 

 ^ of the following conditions exist : Improper drainage ; planting the 

 trees so close together that the ground is continually shaded and kept 

 moist ; continuous use of organic fertilisers ; excessive cultivation ; con- 

 tinuous excessive irrigation, which keeps the soil water-soaked ; and 

 deep planting. 



Trees badly affected with the disease frequently recover if trans- 

 planted to some other location, on apparently similar soil, and given 

 plenty of room. A remarkable instance of this was seen by the writers 

 in a case where 40 acres were planted out some five years ago with 

 large trees affected with foot rot. After three years every tree of the 

 several thousand transplanted to this grove seemed to have fully re- 

 covered. 



Treatment. — Very many attempts have been made, both in Europe 

 and in the United States, to find remedies for this malady. One of 

 the most important discoveries is that it can be prevented by using 

 immune or resistant stocks. It was early noticed that the sour orange 

 and trees of sour orange stocks were almost absolutely exempt from 

 the malady . By using this stock in setting out young grove the dis- 

 ease can be effectually prevented. On high, dry soils, not suited to the 

 sour orange, grape-fruit stock can be used, as it also is quite resistant. 



Many curative treatments prove more or less beneficial, and this has 

 led to conflicting claims as to which is the best. In many cases it 

 has been found sufficient to simply dig away the earth and expose the 

 roots. This probably explains why so many different applications 

 made to the roots seem to benefit the tree. The very act of opening 

 the soil and exposing the roots to the air of itself tends to effect a cure. 

 As the disease is probably caused by a parasite, it is important that no 

 wounds be made on healthy roots in removing the soil. It is desirable 

 to cut away all infected bark and wash the scars with some antiseptic 

 solution, such as sulphurous acid, carbolic acid, or sulphur wash. 

 Where trees are closely planted, it is usually necessary to remove and 

 transplant a part of them to give light and air free access to the roots 

 and trunk. The use of highly organic nitrogenous fertilizers should 

 be avoided, and also excessive or deep cultivation. 



The following is a summary of the treatment recommended for foot 

 Tot : 



1. Remove the earth from about the roots for 2 to 3 feet from the 

 trunk, being careful not to wound the healthy roots. When the groves 

 are furnished with irrigation plants of the kind commonly used in 

 Florida, which are capable of delivering a stream of wai er under con- 

 siderable pressure, the earth should be washed away rather than dug 

 away from the roots. A good way to do this is to first dig a hole some 

 3 feet in diameter and 2 to 3 feet deep about 6 feet from the tree ; then 

 stand on the opposite side of the tree and wash the soil from under the 



