MTURAL CONTROL OF WHITE FLIES IN FLORIDA. 



INTRODUCTION. 



The control of the citrus white fly (Aleyrodes citri R. & H.) by 

 means of the natural enemies already established in Florida has 

 long been a subject concerning which there have been many diverse 

 opinions and insufficiently supported conclusions, but very little defi- 

 nite knowledge. Op})ortunities for extended investigations of the 

 subject were first ofl'ered in 1906 when tlio work was taken u{) inde- 

 pendently by the Bureau of Entomology — as one phase of the whiter 

 fly investigations begim in July of that year — and by the Florida 

 Agricultural Experiment Station. While the field work conducted 

 in the two investigations has been largely along somewhat parallel 

 lines, the duplication of work in the case of such a difficult and impor- 

 tant problem is of great advantage in advancing our knowledge upon 

 wliich final conclusions must be based. 



It is not feasible to present in this publication more than a small 

 selection from the large amount of data whicli have been secured in 

 connection with the investigations of natural control, but it has been 

 the purpose here to present such data as are necessary properly to 

 supj)ort iinportant conclusions. The nature of the more important 

 conclusions is such as to render unnecessary complete discussions of 

 minor topics, which would be necessary under other circumstances. 



The investigations of the parasitic fungi were conducted by the 

 senior author during the season of 1906; by the senior author, by 

 Mr. E. L. Worsham, now State entomologist of Georgia, and by the 

 junior author during the season of 1907; by the junior autlior during 

 1908, and by the senior and junior authors jointly during 1909. 

 Mr. W. W. Yothers has aided at various times in connection with 

 field work and has furnished certain data, as hereinafter specifically 

 credited, in connection with the "white-fringe fungus." Mr. Wor- 

 sham has been specifically credited where his results have been util- 

 ized. Practicall}'^ all of the experimental results included herein are 

 based on the work of the seasons of 1908 and 1909. 



Thanks are extended to Prof. P. II. Rolfs, Dr. E. W. Berger, and 

 Prof. II. S. Fawcett, of the Florida Agricultural Experimental Sta- 

 tion, for the many courtesies extended during these investigations. 

 Acknowledgment is also made of assistance i-endered by Mrs. Flora 

 W. Patterson, mycologist of the Bureau of Plant Industry, to whom 

 many specimens of fungi have been submitted for examination and 

 for information. The colored plate is the work of Mr. J. F. Strauss, 

 of the Bureau of Entomology. 



