August, '11] MORRILL: WHITEFLY CONTROL 375 



The foregoing more or less generalized conclusions applied to the 

 present whitefly situation in Florida lead to the belief that even if 

 an effective natural enemy of the citrus whitefly were already suc- 

 cessfully established in that state and had shown its ability to thrive 

 there, whitefly losses would in all probability amount to three or four 

 million dollars before a condition of commercial control could be accom- 

 pUshed in the average grove. Florida citrus growers have no better 

 justification for inactivity in the control of the citrus and cloudy 

 wing whiteflies pending the results of foreign explorations than have 

 CaUfornia citrus growers for abandoning fumigation and spraying 

 for the control of the red scale {Chrysotnphalus aurantii), purple scale 

 (Lepidosaphes beckii), black scale (Saissetia olece) and the citrus mealy 

 bug {Pseudococcus citri) in view of the -efforts being made by the State 

 Commission of Horticulture to subdue these leading citrus pests by 

 importations of their natural enemies. 



Without going into the details of the history of the importation of 

 the many natural enemies of these scales into California during the past 

 twenty years, it is sufficient to say here that none of the species men- 

 tioned is at present controlled to a satisfactory degree by the intro- 

 duced natural enemies and that the expense of combating these pests 

 in California citrus groves is not materially affected by the introduc- 

 tions. The recognition of this fact does not detract from the true 

 benefits of the work, since the results cannot be measured at present 

 upon such a basis. It seems unlikely that there exists a single species 

 of insect enemy in the case of any of the four pests here referred to 

 which is capable of accomplishing complete and satisfactory control. 

 Combined, certain of the natural enemies may be sufficient but a single 

 minor omission may leave a broad gap between success and failure from 

 a commercial standpoint. It appears to be the present endeavor of 

 the California Commission of Horticulture to supply these omissions. 



During the next five years there is as much likelihood of the whitefly 

 problem in the Gulf Coast citrus regions being temporarily disposed of 

 by a freeze equally disastrous in its consequences to those of the winter 

 of 1894-95 as there is likehhood of a general condition of control by 

 natural agencies being brought about during that time. The citrus 

 growers of Florida, Louisiana and Texas have before them the oppor- 

 tunity to profit by the history of the efforts to control citrus pests in 

 California by means of natural enemies and while efforts to bring about 

 a condition of natural control of the whiteflies should be increased 

 rather than diminished, no time should be lost on account of such 

 efforts in placing the control of these insects upon an organized busi- 

 ness basis and in insuring against the further importation and estab- 

 lishment of undesirable insects. 



