WHITE-PINE BLISTER RUST. 83 
In 1909 it was learned that great quantities of infected young white 
pines had been imported from Europe in 1907, 1908, and 1909. 
(Fig. 1.) With conditions as they appeared to be, it was believed 
that eradication might be possible, and this was attempted. The 
disease was held in check in such shipments of diseased trees as 
could be located. But many could not be located. Moreover, for 
years before, as was subsequently learned, nurserymen and private 
individuals had imported from Europe many infected white pines. 
These we had no means of knowing about until too late, since the 
importers and planters did not inform us concerning them, even after 
the publication of warnings against the disease. Such diseased im- 
portations have been the center s from which most of our large out- 
breaks have started. So far as we can learn no Federal agency has 
imported white pines upon which this disease has been found. 
More complete knowledge of the life history of the fungus has shown 
that it is impossible to eradicate it where both Bibes and white pines 
are native and abundant, after the seciospores are once set free in 
quantity. If both pines and Kibes be removed from a given area 
the disease may be eradicated in that area but it will have escaped 
beyond that area by means of the seciospores. This happened in 
Minnesota and Wisconsin, where all the white pines and Bibes were 
removed from large infected areas. 
The removal of pines has been accomplished in a few cases. Entire 
plantings of imported pine stock were destroyed soon after they were 
found to be diseased, and in these cases Kibes were also removed or 
were absent from the area treated. The forestry officials of the State 
of New York took the lead in this work, destroying 1,200,000 imported 
trees in their nurseries in 1910 and 1911. A number of plantations 
were also destroyed in New York, New Jersey, and Vermont (131, 139). 
As early as 1912, the total destruction of diseased lots of imported 
white pines (133) was urged rather than weeding out only those 
which were visibly diseased. Public opinion would not permit this 
to be done in the wholesale manner that was necessary for efficiency. 
Yet this was the one efficient manner of handling such imported trees 
(136) before generally infected areas had developed. 
SEPARATION OF THE TWO HOSTS. 
The fact that each form of spore will infect but one of the hosts, at 
once indicates that a separation of these hosts will prevent the further 
progress of the parasite within the control area. If the pines only 
are removed, the disease will be likely to die out on the Kibes, since 
it apparently overwinters on them only infrequently; if the Kibes 
are removed, the disease is isolated on that particular lot of pines, 
where it overwinters (if the diseased trees are not also found and 
removed) and produces new crops of seciospores each spring. The 
