BUREAU OF ENTOMOLOGY AND PLANT QUARANTINE 9 
Expenditures by the Mexican Blackfly Committee in the States of 
Nuevo Leon, Tamaulipas, and San Luis Potosi are at the annual rate 
of $250,000. These funds are raised through direct taxation on citrus 
plantings and gasoline sales. 
When an infestation is found by a Mexican survey crew, the control 
and eradication activities are promptly taken over by the Mexican 
Department of Agriculture and the Mexican Blackfly Committee. 
As a result of this closely coordinated program several hundred in- 
cipient blackfly infestations have been found. All of them have been 
either eradicated or greatly reduced in numbers. 
It is anticipated that these intensive surveys of border areas in 
cooperation with the Mexican authorities will prove so effective in 
suppressing infestations that the fly's introduction into American 
citrus groves may be postponed indefinitely, at least until such time 
as well established parasites can effect practical control. 
Texas nursery inspectors are making detailed citrus blackfly in- 
spections along Avith their other duties. Inspectors of the California 
Department of Agriculture are also on the lookout for this pest. 
Sterilization of blackfly infested citrus studied in Mexico 
Dips to destroy the citrus blackfly in packed limes were tested in 
Mexico, in cooperation with the Mexican Secretaria de Agricultura y 
Ganaderia. Lime leaves infested by the citrus blackfly had been found 
in boxes of packed limes shipped to the United States. There is a 
considerable trade in limes. A dip with oils of high paraffinicity and 
viscosity (oils used for processing wool) gave complete mortality in 
tests using more than 100,000 blackfly pupae. It was necessary, how- 
ever, to develop a formula that would kill both the citrus blackfly and 
the Florida red scale. The oils used were not fully effective against 
the scale. Work was therefore shifted to red scale. Exploratory 
formulae look promising but no completely satisfactory dip for these 
two insects is yet available. 
Wild citrus may be significant item in citrus blackfly infestation in 
Mexico 
The relative abundance of blackfly infestation in wild land in 
Mexico has been shown to depend on wild citrus. In moist years the 
blackfly persists on noncitrus plants in the wild, but in drought years 
only on wild citrus. Fortunately, wild citrus has not been found in 
northern Mexico. In 1951, because of drought conditions, infesta- 
tion in wild areas disappeared unless maintained by wild citrus. This 
year with ample rains it has persisted. 
Citrus blackfly control treatments effective 
In the San Luis Potosi area of Mexico citrus blackfly infestation is 
general and heavy. Cleanup would be financially impossible. Ex- 
periments have been directed to commercial control, to tests of trees 
for tolerance to spray treatments, and to large-scale tests of promising 
insecticidal formulations. In one grove commercial control experi- 
ments involving two spray applications doubled production during 
the year. In another the crop was trebled by two applications. Com- 
mercial control has made crops profitable. 
In tests on large plots a new modified xylene-oil-DDT formula £ave 
