February, '12] SPAULDING: DANGEROUS PLANT DISEASES 79 



all of them. The danger from importations then is not limited to the 

 eastern section of the country, but is more or less general throughout 

 the country. As has been stated in my pu])lications upon this disease, 

 several millions of young white pines which were affected with this 

 disease have been imported into the eastern part of this country. 

 Ninety-five per cent or more of the total number of diseased trees 

 which have been imported have come from a single German nursery. 

 The importations from this nursery have for the past two years been 

 reduced to almost nothing, that is there have been only one or two 

 importations each year from this nursery. The disease, however, 

 has been imported from a number of French nurseries. 



The great danger at present is in the continued irresponsible importa- 

 tion of diseased plants wdthout the horticultural inspectors being aware 

 of such importation. The disease is known to have been present in the 

 country since 1903 upon diseased trees, but in every instance where 

 these early importations have been found, Ribes have been absent 

 from the immediate vicinity of the affected trees, so that the disease 

 has not spread. This is entirely good luck, however. The speaker's 

 experience in making inspections has proved beyond any doubt that 

 a single inspection of a diseased lot of trees never can be expected" to 

 result in the removal of all affected trees, that is, repeated inspections 

 must be made. This soon costs more than the total value of the entire 

 shipment of seedlings. 



The second disease from which we are in great danger is that known 

 as the potato wart. This disease is already prevalent in Newfound- 

 land and one or two small adjacent islands. Canada has already 

 quarantined against the movement of potatoes from these islands to 

 the mainland. This means that the United States is bound to receive 

 all surplus potatoes from this district. This disease is characterized by 

 a transformation of the developing tubers into irregular warty black 

 masses which have no resemblance to the original potato. The value 

 of the tuber is entirely destroyed. The most serious feature of this dis- 

 ease is that the organism causing it may live in the soil of an infected 

 field for at least six years without a single crop of potatoes being grown 

 during that time. This practically means that a field once infected 

 will remain infected. Should this disease become established in this 

 country, the potato industry will ultimately be doomed so far as we 

 can judge at present. 



A second European blister rust has been imported into this country 

 already. This is the one occurring upon Scotch pine, known as 

 Peridermium pini. So far as we can judge, this is the most prevalent 

 of the European diseases of this character. It affects not so much the 

 younger trees as it does the older ones, although it is serious where it 



