122 ENTOMOLOGICAL SOCIETY 



orchards and had become rather widely scattered. Shortly 

 after the discovery of the white fly at Marysville it was found 

 also to have established itself locally near Bakersfield, in the 

 southern end of the San Joaquin Valley, and separated only by 

 a mountain range from the main citrus districts of southern 

 California. 



The work of the State Board of Horticulture looking to the 

 extermination of the white fly at these three points of infesta- 

 tion has been thoroughgoing and energetic, and if extermina- 

 tion be humanly possible, it will probably be effected, at least 

 at Marysville and Bakersfield. The wider and orchard infes- 

 tation at Oroville makes the problem here a more difficult one. 

 The principal measure adopted at Marysville has been to cut 

 the trees back to the trunk and strip the latter absolutely of 

 foliage. A careful search was later made of the new foliage, 

 and wherever the white fly reappeared, a second thorough 

 stripping of leaves was made. The white fly is limited to the 

 leaves of the plant, and this stripping, theoretically, should 

 result in extermination. At Bakersfield and Oroville fumiga- 

 tion is being chiefly relied upon, and in all of the places the 

 destruction of many possible host plants other than citrus has 

 been carried out, such as the Chinaberry tree, cape Jasmine, 

 Japanese persimmon, California privet, golden privet, mock 

 orange, Osage orange, and lilac. 



The belief hitherto held by the writer that the white fly could 

 not maintain itself in the comparatively arid climate of Cali- 

 fornia seems to be negatived, in a measure, by this recent expe- 

 rience. Nevertheless, the situation at Marysville is rather 

 exceptional. The city is surrounded on three sides by the 

 Yuba and Feather rivers and these have been so filled up as a 

 result of mining operations that the city, to protect itself from 

 overflow, is surrounded by high levees, and actually lies sev- 

 eral feet below the river level, and has in this way much 

 moister conditions than is normal for this section of the State. 

 Moreover, both Marysville and Oroville enjoy a much heavier 

 rainfall than occurs in the principal orange districts of south- 

 ern California. The infestation at Bakersfield is in a very 

 arid region, but occurs on the highly cultivated estate of Mr. 

 Trevis where, by copious irrigation, a tropical garden is main- 

 tained, and the normal arid conditions are very considerably 

 modified. Nevertheless, there is ample ground to fear an in- 

 vasion or spread of the white fly into the citrus regions of 

 southern California, and the effort to exterminate the pest at 

 the outset of its invasion of the State is thoroughly warranted. 

 That it probably will not be the same pest in California that 



