SUMMARY AND CONCLUSIONS. 71 



There is u wide margin in wliich iiatiinil enemies of the wliite 

 flies may act, a]i])arcntl3' with <?reat activity, but witli no ])ractical 

 benefit to the infested trees. Tlie deceptive appearances thus 

 explained Juive ]>roved a serious hindrance to progress in wlute-fly 

 controL 



It is Avlien several factors concerned in producing mortality among 

 the insects are combined that the most satisfactory results are 

 a})i)arent. 



Asichi from imexplained mortality, fungous diseases are the most 

 important agents of natural control. The brown fungus {JEgerita 

 wehheri Fawcett) and the red Ascliersonia (Aschersonia aleyrodis 

 Webber) are, in the order named, the most eflective parasites of the 

 citrus white fly. The yellow Aschersonia (Aschersonia Jlavo-citrina 

 P. Henn.)is the most effective parasite of the cloudy-winged white 

 fly. The cinnamon fungus ( Verticillium heterocladum Penz.) and 

 the Sporotricluun fimgus {SporotricJium sp.) are of comparatively 

 little importance. The red-headed scale fungus (SpJiserostilbe cocco- 

 phila Tul.) is rarely parasitic upon white flies, while the white-fringe 

 fungus {Microcera sp.) is with little doubt normally saprophytic. 



The fungous parasites thrive only under suitable weather condi- 

 tions during a period of about three months each year; generally 

 spealdng the summer months in the case of the two Aschersonias 

 and the fall months in the case of the brown fungus. 



Their eihcacy m destroying white flies under natural conditions 

 is dependent upon the abundance of the insects; a period of exces- 

 sive abundance always precedes effective temporary control. 



!Mucli damage has resulted in the past from ill-advised attempts 

 to check the spread of wliite flies in newly-infested localities by 

 means of fungous parasites. 



The control of destructive diseases affecting citrus trees and fruit 

 has been interfered with by fungous diseases and much preventable 

 loss tliereby incurred. This interference is due to the fear that the 

 fungicides recommended for the diseases referred to would, if applied 

 to the trees, check the wdiite-fly fungus parasites with injurious results. 



Under natural conditions, without artificial assistance in spreading, 

 the fungi iiave ordinarily, in favored localities, controlled the white 

 fly to the extent of about one-third of a complete remedy through a 

 series of 3'ears. 



The most successful method so far devised for introducing the 

 red and yellow Aschersonias into groves where they do not occur is 

 the spore-6pra\'ing method, first successfully employed and recom- 

 mended by Dr. E. W. Berger. For the introduction of the bro\\ii 

 fungus the brusliing or dipping and the rubbing methods first used 

 by the authors are as successful as any yet discovered, but are not 



