40 NATURAL CONTEOL OF WHITE FLIES IN FLORIDA. 



control, bat due weight should be given to the avithoritativeness of 

 common reports. Otherwise the confusion which arises becomes a 

 decided hindrance to progress. 



OLDER ESTIMATES OF THE NATURAL EFFICACY OF FUNGOUS PARASITES. 



In some respects the subject of the natural efhcacy of the fungous 

 parasites of wliite flies is the most important subject dealt with in this 

 bulletin. Common reports concerning this matter are so frequently 

 erroneous or misleading, as has just been explained, that in addition 

 to the specific observations and records to be given under another 

 heading it is considered advisable to present here quotations from 

 previous publications showing the status of the fungous parasites at 

 different periods since their discovery and the views expressed by 

 various writers concerning their efficacy. 



In a publication previously referred to, submitted for publication 

 in March, 1897, Dr. H. J. Webber makes the following statement : * 



The writer believes it may safely be assumed that the spread of Aschersonia aleyrodis 

 and the brown 'mealy wing fungus will ultimately materially check the ravages of the 

 mealy wing (white fly) and sooty mold. 



According to the publication mentioned. Dr. Webber knew of two 

 instances of apparently satisfactory control resulting from the red 

 Aschersonia and one such instance resulting from the brown fungus. 

 Owing to the comparatively brief period of liis observations and to 

 the checldug of both the white fly and its -parasitic fungi by the 

 freezes of December, 1894, and February, 1895, the fact that the 

 parasites did not maintain a uniform state of control apparently 

 had not come under Dr. Webber's observation at the time of writ- 

 ing the report from which the quotation is taken. However, as a 

 prediction his statement was doubtless fully warranted by the 

 circumstances. 



The next investigator to give attention to the matter of the efficacy 

 of the fungous parasites was Prof. II. A. Gossard. After more than 

 four years of more or less continuous investigations and observations, 

 noting the fluctuations from year to year in the abundance of the 

 insects and of the parasites, he arrived (1903) at the following 

 conclusion : ^ 



I repeat emphatically that while I have no word of condemnation for the man who 

 with intelligence and skill directs nature's agencies so that he secures results from most 

 insects equal to the best (and Ave have some such in Florida), I believe that white fly 

 is an insect that should be fought by everybody by insecticides from the day it is dis- 

 covered in a grove. I admit that there is no spray that will kill white fly and not at 

 the same time inflict injury to the trees, but I am satisfied that the injury is far less 

 than white fly causes, except during exceptional periods when fungous diseases are 

 unusually active. Infested trees that are properly sprayed through many years and 



' Bui. 13, Div. Veg. Phys. and Path., U. S. Dept. Agr., p. 34, 1897. 

 2 Bui. 07, Fla. Agr. Exp. Sta., p. 620, 1903. 



