FUMIGATION" OF CITRUS TREES. 6 
from California. His efforts resulted in determining that the decay 
was almost entirely the outcome of mechanical injury to the skin of 
the fruit during its picking and handling in the packing house. 1 
Oranges are washed primarily to remove the sooty-mold fungus that 
grows in the so-called honeydew excreted by the black scale. Dr. 
Powell demonstrated that the decay in washed fruit is much greater 
than in unwashed fruit. This led the fruit growers to understand 
that the necessity of washing fruit should be avoided by controlling 
the scale in the orchard. 
As a direct result of Dr. Powell's investigations, and knowing from 
past experience that the distillate spray and the Scutellista parasite 
were inadequate to control the scale, fruit growers took a renewed 
interest in fumigation. This led to a demand for an investigation 
of this process, to be conductedby the United States Department of Agri- 
culture, and the following year, 1907, the writer was detailed to this 
field. The fumigation practice was then in a very chaotic condition 
as the outgrowth of years of use without any special effort to have 
the process standardized. Indeed, it was a favorite pose of many 
professional fumigators to veil their operations in mystery in order 
to secure the reputation of being authorities in a practice which they 
made to appear complicated and difficult "of understanding. Conse- 
quently the growers, for the most part, although arranging to have 
their orchards fumigated, took no interest in a procedure which they 
little understood. 
In the face of this situation the first reports of this investigation 
given out in 1908 attracted the immediate attention of the fruit 
growers. After gaining a general understanding of the process of 
orchard fumigation the growers in many localities have become much 
interested and subsequently have adopted or have caused to be 
adopted the more important recommendations of this investigation. 
This adoption of better methods has led to more satisfactory work 
generally. The grower has immediately seen the advantage of better 
methods, with the result that where formerly many were with diffi- 
culty induced to have their trees fumigated, to-day the successful 
orchardist needs no inducement whatever, but, on the contrary, re- 
quires that his trees be treated whenever their condition appears to 
demand it. This public interest in fumigation has made it one of 
the very live topics in the horticultural field in southern California 
to-day. 
EXTENT TO WHICH FUMIGATION IS PRACTICED IN CALIFORNIA. 
Commercial fumigation of citrus trees is confined to six counties 
of southern California, viz, Ventura, Los Angeles, Orange, Riverside, 
San Bernardino, and San Diego. In these counties about 85 different 
i Bui. 123, Bur. Plant Ind., U. S. Dept. Agr., 1908. 
