LOSSES FROM WHITE FLY PREVENTED. 59 



ECONOMY OF TREATMENT BY FUMIGATION. 

 LOSSES PREVENTED. 



-When once the white fly (figs. 8, 9) is 

 ((uantity in a grove, much benefit will 



Losses from the white fJy.— 

 reduced to an inconsiderable 

 result from careful inspec- 

 tions and fumigations of sin- 

 gle trees, or groups of trees, 

 from time to time wherever 

 the insects are found to be 

 multiplying. This will greatly 

 delay the time when the mul- 

 tiplication of the insects shall 

 have made a general treat- 

 ment again necessary. This 

 practice is followed in Califor- 

 nia in the control of various 

 scales. In well-cared-for 

 groves, or where the county 

 horticultural commissioners 

 require it, scales are kept in 

 complete subjection by fumi- 

 gation and the ai)pearance of 

 only a few live scales on a tree is considered a reason for fumigating 

 it and perhaps, also, surrounding trees as well, although these may 



The best results from fumiga- 

 tion are obtained when once the 



Fig. 8. —White fly {Aleyrodes citri) : a, Orange leaf, show- 

 ing infestation on under surface, natural size; b, egg 

 c, same, with young insect emerging; d, larval insect 

 e, foot of same; /, larval antenna; g, scale-like pupa 

 h, pupa about to disclose adult insect; i, insect escap- 

 ing from pupal shell; ;, leg of newly emerged insect, 

 not yet straightened and hardened. All figures ex- 

 cept a greatly enlarged (reengraved from Riley and 

 Howard). 



appear entirely free from the pest. 



various pests are brought under 

 control by continuing the prac- 

 tice as a preventive rather than 

 as a remedy. In other words, 

 when conditions for successful 

 fumigation for the white fly are 

 favorable or after they have 

 been made so,''' fumigation can 

 be practiced with such success 

 that all damage from tlie white 

 fly will be obviated. When once 

 the practice has been adopted a 

 grower should not wait until the 

 foliage is blackened by the in- 

 sects before fumigating the second time. It would be far more eco- 

 nomical to fumigate regularly once in two years, and prevent all 

 blackening of the foliage, than to fumigate once and wait until the fly 



Fig. 9.— White fly {Aleyrodes citri): a, AVinged male 

 insect, with enlarged view of terminal segments 

 at b: f , dorsal view of winged female, with enlarge- 

 ments of ovipositor, head, antenna, wing margin, 

 and leg at d, e,f, g, h, i. (Reduced from Riley and 

 Howard.) 



« See discussion of this subject, pp. 9-14. 



