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 honey dew 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, tobe conductedby the LnitedStates 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 



1 Bui. 123, Bur. Plant Ind., U. S. Dept. Agr., 1908. 



