268 



THE MONTHLY BULLETIN. 



which centers of infection have been cleaned up. The following figures show the 

 number of infected trees found each month in Florida, and furnish ample evidence 

 that the disease is decreasing rapidly : 



Number of Grove Trees Found Infected With Canker, Per Month, Since the Work 



Began in May of 1914. 



1915 



1917 



May 108 



June 160 



July 275 



Aug... 1,313 



Sept — 767 



Oct 565 



Nov — 773 



Dec 366 



Jan. 306 



Feb „ 165 



Mar 444 



April 408 



May 1,042 



June 772 



July 651 



Aug - — 1,345 



Sept. -- 618 



Oct. 214 



Nov 494 



Dec 256 



It is confidently anticipated that the continuation of the eradication work in 

 Florida for two more years upon the present scale will result in practical eradication 

 and that but few if any infections will be found at the end of that period. Owing 

 to the fact that the disease may under certain conditions remain dormant for several 

 months before becoming visible, the inspection of citrus properties in areas where 

 the disease has occurred will necessarily be continued for several years longer as a 

 precaution. In fact, it is a question whether inspection should ever be entirely 

 discontinued in the citrus-growing areas of the United States. 



Several important lessons have been taught us by the experience with citrus 

 canker. The first of these is the necessity for an efficient quarantine service against 

 all dangerous insect pests and diseases, unknown as well as known. California 

 growers may ascribe their good fortune in thus far escaping first-hand experience 

 with this dread disease to the excellent quarantine which has been maintained by 

 the California Commission of Horticulture. 



The second lesson is that sanitary methods and antiseptic precautions in dealing 

 with a disease of plants are as necessary as the use of these same measures by 

 physicians when dealing with infectious diseases of human beings. 



Finally, and perhaps the most important of all, is the demonstration of the possi- 

 bility and practicability of completely eradicating a plant disease over a considerable 

 area and that such eradication, even at the expenditure of comparatively huge sums 

 of money, is a good investment and much better than carrying on a partially-effective, 

 prolonged warfare by means of so-called "control" measures. 



THE WHITE PINE BLISTER RUST AND THE CHESTNUT 



BARK DISEASE. 



By E. P. Meinecke, Forest Pathologist, Office of Investigations In Forest Pathology, 

 Bureau of Plant Industry, San Francisco, Cal. 



One of the outstanding features of progress in the nineteenth century was the 

 tremendous impetus given to international commerce through means of rapid trans- 

 portation and a corresponding specialization of industries. In this give and take of 

 products man has not always been able to guard against the incidental movement 

 back and forth of undesirable or injurious organisms of the animal and vegetable 

 kingdom. Often he has become aware of the presence of the enemy only when it 

 was too late. Ignorance and negligence have in the past permitted the introduction 

 of the phylloxera into the vineyards of Europe, with its disastrous results, and the 

 invasion of the United States by a host of injurious parasites and pests. 



