16 BULLETIN 647, U. S. DEPARTMENT OF AGRICULTURE. 



on the trees it may be of great importance as a conveyor of citrus 

 diseases, but the actual extent to which it increases the spread of 

 diseases as yet remains to be determined. Since almost all the 

 damage so far caused by the ant has been through its relations with 

 the injurious citrus insects, this damage must be solely in the nature 

 of an intensification of the work of these insects. Only that portion 

 of such injury in excess of that normally caused by these insects can 

 be due to their relations with the ants. It is, therefore, necessary to 

 bear in mind that only a few of the citrus-infesting insects are of 

 importance, and they cause practically all of the insect injury. The 

 ant must be proved to enhance greatly the damage done by these major 

 pests before a case can be made against it as a destroyer of orange 

 trees. The major pests of citrus in Louisiana are four species of 

 armored scale insects, the citrus white fly, and the rust mite, any one 

 of which will cause more loss than all of the lesser pests, including 

 the soft scales and the aphids, together. 



RELATIONS WITH THE AR ORED SCALES. 



Status of the Armored Scales of Citrus in Louisiana. 



The four important armored scale insects of citrus in Louisiana 

 are, in the order of their importance, the purple scale (Lepidosaphes 

 bec7cii Newm.), the chaff scale (Parlatoria pergandei Comst.), the 

 long scale (Lepidosaphes gloverii Pack.), and the white scale (Chi- 

 onaspis citri Comst.). The purple scale is the most numerous and 

 destructive of the citrus scales, infesting fruit, leaves, branches, and 

 trunk, and generally incrusting the branches and trunk along with 

 the chaff and long scales. The chaff scale infests nearly every budded 

 bearing tree in the State, incrusting especially the trunk and larger 

 branches, and at times overflowing onto the fruit and leaves in con- 

 siderable numbers. The long and white scales also occur on most of 

 the trees, but do not become so numerous as the first two, either of 

 which would outrank them both as pests. The status of these scales 

 does not seem to have changed much, excepting perhaps that of the 

 white and chaff scales, in the last 12 or 15 years. The purple scale, 

 according to Morgan, 1 was considered one of the most dangerous 

 scales in the State at that time (1893). The white scale, however, 

 considered by Morgan 2 as one of the most destructive of the scales, 

 causing bursting of the bark, does not now get so numerous as the 

 others and causes little damage. The chaff scale, which Morgan 

 states was not recognized as very destructive, 3 now must be accorded 

 second place to the purple scale as a scale pest of citrus in the State. 

 Dr. Howard states that the chaff scale was the preponderating scale 

 of citrus at a certain plantation on Bayou Teche as early as 1830. 



1 See Stubbs and Morgan, op. cit., p. 57. 2 Ibid., p. 64. 8 Ibid., p. 62. 



