127 



THE PRINCIPAL DISEASES OF CITRUS FRUITS 



IN FLORIDA. 



By Walter T. Swingle and Hedbert J. Webber. 



Iteprinted from Bulletin No. 8 of U. S. Department of Agriculture 

 Division of Vegetable Phijsiology and Pathology. 



Introduction. 



It is the purpose of this bulletin, to give in as brief and concise a 

 manner as possible, an account of some of the principal diseases of 

 citrus fruits, especially those 03curing in Florida. The following are 

 the diseases which we will endeavour to describe : Blight, die-back or 

 exanthema, scab or verrucosis, sooty mould, foot root or mal-di-gomma, 

 and melanose. 



The diseases of citrus fruits have received more or less attention 

 from the Department, through the Division of Vegetable Physiology and 

 Pathology, since the year 1886. In 1891 Prof. L. M. Underwood was 

 gent to Florida to make a preliminary study of this subject. Later 

 the same year one of the writers, with Dr. Erwin F. Smith, was sent 

 to Florida to carry on further studies, especially on blight, and the 

 following spring the former returned to continue the work. In the 

 fall of 1892 a slightly increased appropriation enabled the Department 

 to station both writers regularly in Florida. A laboratory especially 

 erected for the purpose was donated by the ci tiizens of Eustis, Fla., and 

 this point was made our headquarters. Since the completion of the 

 building both laboratory and field investigations have been carried on 

 continuously, with highly gratifjang results. Melanose, an entirely 

 new disease, has been studied and remedies for it discovered. Satisr 

 factory remedies or preventives have also been found for all the othee 

 diseases mentioned above, foot rot being the only one which could b- 

 said to be under control when the work was commenced. Much infor- 

 mation has been collected in relation to the causes of the various dis- 

 eases and their effects on the plants attacked. 



BLIGHT. 



This disease, also called wilt and leaf curl, is found only in Florida, 

 and so far as known at present is incurable. Nearly all citrus frai<i8 

 are liable to it, but in different digrees. Trees grown on light ham- 

 mock soil are most susceptible, but no locality in the State is entirely 

 exempt. The malady has been known for at least twenty and possibly 

 twenty-five years. The first reliable account of it, however was pub- 

 lished in 1891 (1) by Prof. L. M. Underwood. 



Blight never attacks trees until they have attained considerable size 

 and have begun to bear fruit. In any given grove usually only a small 

 per cent of new cases occur each year, but the fact that the disease is 

 apparently incurable and that it attacks the oldest and most vigorous 



(1 ) Journal of Mycology, Vol. VII, pp. 32-34. 



