SCALE INSECTS AND MITES ON CITRUS TREES; 



INTRODUCTION. 



The scale insects, or bark-lice, are the most important insect enemies 

 of citrus, as they are also of most other subtropical plants. They are, 

 as a rule, small and inconspicuous singly, but they multiply so rapidly 

 that very soon an entire plant becomes infested — trunk, limbs, leaves, 

 and fruit. The attacked tree is rarely killed outright, but its growth 

 may be almost completely checked and its fruit rendered valueless. 



Next in importance to the scale insects are the mite enemies of the 

 orange and lemon, as represented b}^ the mite which causes the rusting 

 of the orange in Florida and the silvering of the lemon in California, 

 and also the leaf mite, known from its coloring as the six-spotted mite 

 of the orange. These mites occur with the scale insects, are subject 

 to similar remedies, and may properly be considered in the same 

 connection. 



Of very great importance to the" Florida grower of citrus fruits is 

 the so-called white fly, the latter not being a scale insect in the ordi- 

 nary acceptation, but in the essential features of life history and habits 

 coming in the same category, and hence properly considered with the 

 true scale insects. 



There are many insect enemies of citrus plants other than the scale 

 insects and mites, but, for this countrj^, at least, these others, in the 

 main, have no great economic importance, or are only very occasionally 

 abundant enough to be especially destructive. 



Occurring about the orange and other citrus trees will also be seen 

 many other insects which play a beneficial role, preying upon or para- 

 sitizing the scale insects living on these trees. It is very important to 

 make the acquaintance of these beneficial species, more particularly to 

 avoid, whenever possible, killing them in the warfare waged against 

 the injurious ones. 



« No one can discuss the insect enemies of citrus plants without acknowledging 

 indebtedness to the very comprehensive and valuable work , now long out of print, 

 prepared by the late H. G. Hubbard and published by this Department in 1885, 

 under the title "Insects affecting the orange." The practical side of Mr. Hubbard's 

 work is especially to be remembered, and particularly that he devised kerosene-soap 

 emulsion, which, with allied washes, has for many years been the leading means of 

 controlling scale insects. 



59729— Bull. 172—08 2 ^ 



