80 THE MONTHLY BULLETIN. 



CONCLUSION. 



No attempt has been made in this paper to give a full account of the 

 Mediterranean fruit fly. Only a few of many interesting phases of the 

 problem have been touched in an attempt to call attention, possibly in 

 a new manner, to the seriousness of the situation threatening the more 

 tropical portions of the mainland United States, and to indicate that 

 everything is being done that can be done by the federal and state 

 officials to prevent establishment in California. With the fruit fly 

 knocking continuously at the gates of San Francisco and Los Angeles, 

 it behooves all interested to inform his neighbor concerning the fruit 

 fly, for it is the unthinking and uninformed traveler returning from the 

 Islands — perhaps with a few exotic (and infested) fruits in his baggage 

 or pockets — that is most likely to introduce the pest to California. 



PRUNING FRUIT TREES. 

 "With Special Reference to the Apple. 



By W. H. Volck, County Horticultural Commissioner, Watsonville. 



For the past four years much of my time has been devoted to develop- 

 ing a satisfactory system of pruning for apple trees under California 

 conditions. Such pruning involves many difficulties, and not only must 

 the tree be kept properly thinned, but special care should be taken to 

 prevent infection by the wood-rot fungus. 1 Wood rot is one of the 

 principal enemies of California fruit trees, and is a factor which largely 

 determines the life of an orchard. 



Wood rot is especially in evidence in the Pajaro "Valley, the locality 

 where this experimental work has been conducted. 



These pruning experiments were started in connection with the 

 "Apple Powdery Mildew Investigations," conducted jointly by the 

 United States Department of Agriculture and the Santa Cruz County 

 Horticultural Commissioner. 2 As such, the pruning was especially 

 designed to remove mildew-infested twigs in order to facilitate the 

 control of this disease. 



From this beginning the work has been continued as a general study 

 of pruning methods, and we have been especially fortunate in securing 

 a plot of Yellow Newtowns on which these experiments could be con- 

 tinued from year to year. 3 



Considerable progress has been made towards a satisfactory solution 

 of the pruning problem, and while the investigation is by no means 

 complete, it appears advisable to make the findings public. In doing so 

 I am aware of the difficulty involved in description of these methods in 



•A species of Pohistictus most commonly found in the wood-rot cankers has been 

 described by C. J. Rodgers, University of California, 1314, in Studies on Sappy Bark 

 Disease of the Apple. This work is also referred to by W. T. Home, Circular No. 137. 

 California Agricultural Experiment Station. 



"The beginning of the pruning work was referred to in Bulletin 120, Bureau of 

 Plant Industry of U. S. Department of Agriculture, entitled Apple Powdery Mildew 

 and Its Control in the Pajaro Valley. 



'This experimental work has been conducted in a block of Yellow Newtown trees 

 located on the C. H. Rodgers estate near Watsonville, California. The work was 

 begun during the life of Mr. Rodgers, who extended every aid possible. This same 

 policy has been continued by his heirs, and has made possible such success as we 

 have attained. 



