614 INSECT PESTS OF FARM, GARDEN AND ORCHARD 



amount of agar improved the consistency of the cultures so that 

 they can be shipped without contents of the bottle becoming 

 mixed up, or disarranged. The presence of the agar, furthermore, 

 permitted allowing the contents of the bottles to cool and harden 

 in a sloping position, resulting in what has been called a 

 "Sweet potato-agar-slant" which has certain advantages for 

 manipulation in the laboratory 



Control of Scale Insects, Mealy-bugs and Whitefly. 



Three general methods for the control of the above insects are 

 used. They are, spraying, practiced in California and in Florida 

 with equal success; fumigating, practiced in California, but not 

 so successful under Florida conditions on account of the large 

 amount of rainfall; and control by the encouragement and dis- 

 tribution of fungi parasitic on the insects, this method being 

 adapted to Florida conditions rather than to those which obtain 

 in California, since these fungi usually are favored by excessive 

 amounts of moisture. 



Spraying. Spraying for the insects in question is rather 

 increasing in favor as new methods and materials are being per- 

 fected. Formerly it was considered impossible to do successful 

 spraying for these insects because of the close heads and dense 

 foliage of the citrus trees and their lack of a dormant period 

 which would permit the use of insecticides stronger than the 

 foliage could stand and would also permit more thorough treatment 

 of the trunk and branches than is possible where the tree retains 

 its foliage for the entire year. 



However, sprays have been developed which will kill the insects 

 without injury to the foliage and there are spraying machines with 

 which these sprays can be applied thoroughly with careful labor. 

 Lack of success is likely to be due to faults in the application of the 

 sprays rather than to the inefficiency of the method. 



In spraying for all the insects in this list several things must be 

 considered. First is the fact that these are all sucking insects 

 which must be hit by the spray to be killed; second is the fact 

 that there are several stages, some of which are more easily killed 

 by spray materials than are others so it is necessary to have a 

 reasonable knowledge of these stages in order to apply the sprays 

 when they will do the most good ; and third, the fact that they 



