4 BULLETIN 647, U. S. DEPARTMENT OF AGRICULTURE. 



characterizes the healthy orange tree, and production was far below 

 the standard for trees of their average age. During the blossoming 

 period the flowers were often somewhat too numerous and con- 

 spicuous, a condition which characterizes a " sick " tree, and dying 

 and dead trees were numerous throughout the district. 



The apparent cause of the diseased condition of the trees was 

 often traced to heavy infestations by scale insects and white flies, 

 but obviously, in some cases, other factors contributed to this condi- 

 tion. Many orchards not invaded by ants exhibited the same symp- 

 toms as those overrun by ants. Manifestly, the amount of injury 

 done by the ant must be distinguished from that due to other causes, 

 and this involves a knowledge of the general conditions characteriz- 

 ing citrus culture in Louisiana. 



The investigation therefore was planned to cover, first, a thor- 

 ough study of the habits of the Argentine ant in relation to orange 

 trees, and, second, a study of the cultural practices and other condi- 

 tions which might affect the successful raising of oranges in Lou- 

 isiana. An experiment in the reclamation of an ant-invaded and 

 practically abandoned orchard was conducted to determine what 

 might be done in the way of making such orchards profitable. The 

 problem of ant destruction and control in the orchards was taken 

 up at the beginning of the investigation and continued throughout 

 its course. 



GENERAL ACCOUNT OF ORANGE CULTURE IN LOUISIANA. 



Louisiana is, perhaps, the oldest citrus-producing State in the 

 Union. Orange trees have been cultivated there for at least 200 

 years and, perhaps, longer, at least one introduction having been 

 made from Cape Haitien (Cap Francois), Santo Domingo, by the 

 original French concessionaires, who arrived in Louisiana in 1718, 1 

 and it is probable that citrus trees had been grown there by the 

 Spanish colonists previous to this introduction. 



During the long period that has elapsed since this introduction 

 orange trees have suffered occasionally from severe freezes, and 

 several times have been killed to the ground. Freezes of this ex- 

 treme sort, occurring in the period from about 1718 to 1806, are 

 mentioned by Le Page du Pratz, 2 Robin, 3 and several other writers. 

 Similar killing freezes have occurred during the past century, one, in 

 1835, killing every orange tree from the shores of the Atlantic to the 

 Mississippi ; 4 others, the last one of which at least was equally diss 



1 Le Page du Pratz. The History of Louisiana. Translated from the French of M. 

 Le Page du Pratz, v. 2, p. 17-18. London, 1763. 



2 Op. cit., v. 2, p. 17. 

 *Op. cit., p. 474. 



* De Bow, J. D. B. In Review, v. 18, p. 609. New Orleans, 1855. 



