FUNGI PARASITIC UPON ALEYRODES GITRI. 



BY 



HOWARD S. FAWCETT, 

 Plant Pathologist, Florida Agricultural Experiment Station. 



I. INTRODUCTION. 



Since taking up the investigation of Citrus diseases in the fall of 1905, 

 in connection with work in the Florida Experiment Station, the author has 

 given considerable attention to the study of the fungi parasitic on Aleyrodes 

 citri R. & H., and on scale insects. Since the beginning of the work three 

 species of fungi have been discovered to be parasitic upon the larvae and 

 pupae of Aleyrodes citri; two of these, Aschcrsonia flavo-citrina, and an 

 undetermined species of Microcera, were first noticed by Prof. P. H. Rolfs, 

 and the third, Vcrticillium hctcrocladum, by the author. With the addition 

 of these three, the number of known fungus parasites of this insect is in- 

 creased to six, namely: 



1. Aschcrsonia alcyrodis Webber, 



'2. Aschcrsonia flavo-citrina P. Henn., 



3. J^crticilliuni hctcrodadnin Penz., 



4. Spkaerostilbe coccophila Tul., 

 .">. Microcera sp., 



(>. The sterile Brown fungus of Webber. 



Cultures of all these fungi except the Brown fungus have been grown in 

 the laboratory by the author. One of these, Sphaerostilbe coccophila., had 

 been previously studied in pure cultures by P. H. Rolfs, who published his 

 results in Bulletin 41 of the Florida Experiment Station under the title of 

 "A Fungus Disease of the San Jose Scale". For this reason a further study 

 of this fungus in cultures was not undertaken, and it is, moreover, only 

 rarely parasitic upon Aleyrodes citri. 



It is the purpose of this thesis, after a brief review of previous investiga- 

 tions of the fungus parasites of insects, to describe the results of recent study 

 of the fungi that are parasitic upon Aleyrodes citri in Florida. With the 

 description of each fungus there is given its distribution and the names of 

 its insect hosts. A bibliography of the six fungi is added. The illustrations, 

 except Figs. 1, 2, and 42, are original. Technical descriptions and a general 

 review of previous literature, when any such has been published, are in- 

 cluded with the account of each fungus. 



ENTOMOGENOUS FUNGI. 



The fact that certain low forms of plant growth, such as fungi and 

 bacteria, are at times the cause of the destruction of great numbers of 

 insects, has created much popular as well as scientific interest for many 



