304 



THE MONTHLY BULLETIN. 



What has been stated about spraying the common whitefly applies quite the same 

 for the cloudy-winged species, although the latter is a few weeks later in its develop- 

 ment. This rule for spraying applies equally well for the woolly whitefly, but, as 

 can be seen from the diagram (Fig. 100), the time for spraying does not coincide so 

 well with that of the other whiteflies. 



The oil emulsions used are made from paraffine oils testing 24-28 degrees Baurne. 

 Soap is the emulsifying agent, and the dilution used in spraying the trees is 1 per 

 cent oil in winter, to as low as i per cent in spring or summer. Several commercial 

 brands of oil emulsions, or miscible oils, are also used effectively. Fish-oil soap, or 

 other soaps, 1 pound to 5 or 6 gallons of water, are excellent when applied at the 

 light time, i. e., before the larvae reach the advanced fourth stage and pupal stage. 



FUMIGATION. 

 The practice of fumigating for insects has not become established in Florida, 

 although at least two apparently successful attempts to introduce it have been made. 

 The inherent difficulties are: the shortness of the season (December, January and 

 February) during which fumigation can be conducted; night work; heavy dews and 

 winds; greater skill required; greater overhead expense, etc. 



»■*•* 





m 



Fig 105 A. Fourth stage larva of the cloudy-winged whitefly, photographed by 

 transmitted light. Enlarged about 45 times. B. Fourth stage larva of the common 

 whitefly, photographed by transmitted light. 

 Exp. Station, Bui. 97.) 



Enlarged about 45 times. (Courtesy Fla. 



LIST OF CITRUS WHITEFLIES. 1 

 Introduced Species. 

 1. Common whitefly, Dialeurodcs oitri (Ashmead). Formerly Aleyrodes citri. 

 Introduced from Orient, probably India. Found in India, Ceylon, Japan, China and 

 United States Kirkaldy, according to Quaintance and Baker (reference in footnote), 

 reports it as present in' Mexico, Chile and Brazil. In the United States it is widely 

 present in the Gulf States, Georgia, South Carolina, and farther north on chinaberry, 

 cape jasmine and privet. It was discovered in 1!K)7 at Marysville. Sacramento and 

 Oroville, California, but is said to have been eradicated, except at Marysville. where 



■In the preparation of this list free use has been made of the paper • by A. L. 

 Quaintance and A. C. Baker, Jrnl. Agric. Research, Wash., D. C. Vol. VI, No. 12, 

 June 19, 1916, U. S. D. A. 



