72 NATURAL CONTROL OF WHITE FLIES IN FLORIDA. 



SO reliable as the spore-spraj'ing method for the Aschersonias. The 

 infections secured by artificial means of introducing fungi, while 

 successful in introducing the fungi, have thus far proved of little 

 or no avail in increasing their efficacy after they have once be- 

 come generally established in a grove. Experiments by the 

 authors, and by citrus growers in cooperation with the authors, 

 mvolving the treatment of thousands of trees with suitable "checks" 

 or "controls" have shown that when fungus (red or yellow Ascher- 

 sonia) even in small quantities is present in a grove there is no cer- 

 tainty that from three to six applications of fungous spores in water 

 solution will result in an increased abundance of the infection on the 

 treated blocks of trees by the end of the season. In some of the 

 most important and carefully planned and executed experiments 

 the fungus has increased more rapidly in sections of the groves which 

 were not sprayed with spore solutions than in the experimental 

 blocks. In no case has practical benefit been observed to result 

 from efforts to increase the efficacy of the fungi in groves where 

 they previously occurred. The above remarks apply especially to 

 the Aschersonias. With the brown fungus, efforts to increase the 

 efficacy have been equally disappointing from a practical standpoint. 



As a result of the investigations reported herein and of observa- 

 tions and experience covering a period of four years the authors 

 conclude that there are at present no elements of natural control 

 herein dealt with which can be relied upon to give satisfactory re- 

 sults. Under present conditions it is unquestionably more profit- 

 able to depend upon artificial remedies.^ 



There are, however, certain circumstances under which fungous 

 parasites may be used to advantage. First may be mentioned the 

 comparatively few citrus groves located in hammocks, with trees 

 growing without regularity and with conditions such that fumiga- 

 tion or spraying with insecticides would be impracticable.^ Second 

 are those groves wiiich are so situated that .the failure to more 

 than partially control the white flies will not interfere with the con- 

 trol of the insects in other groves and which for any reason it is 

 impracticable to place on the most profitable basis of productiveness. 



Wliile it is recognized that everything possible should be done to 

 secure and to test every procurable and possible enemy of botli the 

 citrus white fly and the cloud}-- winged white fly, citrus growers in 

 Florida should not await the outcome of this work with inactivity 



1 See Bui. 76 and Circular 111, Bur. Ent., U. S. Dept. Agr. Fumigation has already been dealt with 

 in publications of the bureau. Spraying and other matters connected with artificial methods of control 

 will be treated in later publications. 



2 Since the above was written the brown fungus has been so effective in controlling the white fly ra 

 certain very low-lying hammock groves in Lee County that it must be conceded this fungus has made 

 artificial remedial measures unnecessary. Such groves, however, are an exception to the rule at the 

 present time. 



