6 FARMERS' BULLETIN 928. 



years. During 1916, however, the insect was very scarce, even in the 

 worst ant-infested orchards of Los Angeles, Riverside, and Ventura 

 Counties, there seldom being more than one or two scales per tree. 

 The chief factor in their control in California seems to be insect 

 enemies, chiefly the Australian lady-beetle, 1 a parasitic fly, 2 and lace- 

 winged insects; 3 but there appears to bo some other unknown factor 

 assisting. 



Black scale* In California the black scale is rated as the most 

 important of all the citrus scales. It is generally hold in check by 

 annual or biennial fumigation. Whether ants are in- attendance or 

 not, infestation by this scale often becomes very severe and capable 

 of causing a heavy loss of crop after a single season in -which fumiga- 

 tion has been neglected. Sometimes infestation is greater in trees 

 where there are no ants than in others of the same age and condition 

 overrun by ants. The black scale has quite a number of natural 

 enemies, including one or two intermittently effective internal para- 

 sites, but these enemies do not seem capable of keeping it under con- 

 trol; hence interference by the ant with the work of these enemies 

 does not accelerate greatly the increase of the scale. 



Soft brown scale. 5 The soft brown scale is a favorite of the Ar- 

 gentine ant. In Riverside County, Cal., this scale appears to have 

 increased considerably in certain ant-infested groves, especially 

 where for a long time fumigation has been neglected. Ordinarily it 

 is controlled along with other scales by fumigation and no special 

 treatment for the ant is needed. In Los Angeles and Ventura Coun- 

 ties both the soft brown scale and the closely allied citricola scale 6 

 are scarce in ant-invaded as well as in ant-free orchards. On more 

 isolated ornamental trees, bordering some of the streets of Pasadena 

 where the ants have become numerous, the scales are much more 

 numerous than where there are no ants. 



The control of scales by fumigation in California makes it im- 

 probable that the ant will increase seriously the damage from the 

 black and soft brown scales in those orchards where fumigation is 

 conducted regularly, although annual fumigation may become neces- 

 sary in all groves invaded by the ants. The control of the mealy- 

 bugs will be facilitated greatly, and in many cases accomplished 

 fully, by the protection of the trees from ants. There are no present 

 indications that the ants will cause the fluted scale to become again 

 a menace to the State. 



cardinal! ft Muls. 



2 Cryptochaetum mcnophleM Skuso. (Identified by Frederick Knab.) 



3 Chryxopa calif orica Coq. and possibly others. 

 * Saissetia oleae (Bern.). 



c Coccus hesperidum L. 



6 Coccus citricola Campbell. 



