28 NATURAL CONTROL OF WHITE FLIES IN FLORIDA. 



Orlando liave demonstrated, however, that ordinarily the overrun- 

 ning of from 20 to 90 per cent of the pustules does not prevent the 

 fungus from spreading rapidly when the weather conditions are 

 favorable. The Cladosporium spreads most rapidly during dry 

 weather and upon leaves bearing many pustules of the Aschersonia. 



The yellow Aschersonia pustules in all ages and conditions are 

 subject to the attack of the Cladosporium. (See PI. VI.) The former 

 is frequently so closely followed by the latter that even when spread- 

 mg rapidly practically all of the Aschersonia pustules show the 

 beginning of the h3'perparasitic attack before they reach more than 

 one-fourth of their normal size. 



During 1907 and 1908 the Cladosporium v/as especially active in 

 August and October. In 1907 its spread was unusually rapid 

 between October 17 and 31, during very dry weather, and by Novem- 

 ber 15 of the same year had so overgrown the yellow fungus in one 

 nursery at Orlando that 92.6 per cent of the pustules were affected. 

 This estimate is based on the exammation of 50 leaves upon which 

 there were 3,110 pustules of the yellow Ascliersonia. Again, between 

 August 6 and 13, 1908, when no rain had fallen since July 28, it 

 spread with such rapidity as to render useless numerous experiments 

 started in July at Drennen. During the summer of 1909, when the 

 rain was more abundant than during 1907 or 1908, the Cladosporium 

 did not spread with such rapidit}^ in any of the groves at Orlando. 



THE BROWN FUNGUS. • 



{Mgerita wehberi Fawcett.) 



Dr. 11. J. Webber, then of the United States Department of Agri- 

 culture, first discovered the brown fungus, parasitic upon the immature 

 stage of the citrus white fly, in March, 1896, in the grove of J. H. 

 Viser, Manatee, Fla. Dr. Webber states that while the spread of the 

 fungus was phenomenal from March to December of tliat year and 

 killed so many larvsB and pupse that the fruit was clean, lie was 

 unable to discover it in any of the surrounding groves heavily infested 

 with the fly. Although a thorough study of the fungus was made by 

 its discoverer at several seasons of the year, no trace of fructification 

 was found; hence it was impossible to determine its relationship. 

 The fungus was, therefore, popularly named the browai mealywing 

 fungus, or, as it is now more commonly called, the brown fungus. 



During the past three years the authors have noted the frequency 

 of the occurrence of patclies of minute brownish spores on leaves 

 infected with this fungus, arising apparently from its ground myceUum 

 As these spore patches occurred only upon leaves infested with the 

 fungus and upon no otlier leaves no matter how heavily coated with 

 sooty mold, it was concluded that tliey must be the fruiting bodies of 

 the fungus. A specimen leaf was sent to Mrs. Patterson, the mycolo- 



