Plant Diseases of 1901 . 
19 
the diseased parts. These masses are sometimes mistaken for 
blossoms or fruit of the tree, and in some sections are known as 
cedar apples. They are moist and gelatinous in texture during 
damp weather, so that the first spores readily germinate where they 
are borne. These in turn give rise to minute secondary spores, which 
are readily blown about by the wind and which can only grow on 
some plant that is a member of the family to which the quince be¬ 
longs. When they chance to fall on a quince tree, and the condi¬ 
tions are suitable for germination, rust is produced. The cedar 
apples become dry and withered during sunny weather, consequently 
the dissemination of spores is stopped until another rain softens the 
mass. Thus it happens that the period of infection may extend 
over a considerable length of time. 
The spores that are borne on the quince trees can only grow 
when they in turn are carried to the cedars, thus starting new 
sources ot infection. 
There are a number of species of this fungus and all of them 
pass the second stage on some member of the same family of plants. 
The apple is sometimes attacked, and the service berry that grows 
in the foot hills and mountains is often badly diseased. Fig. 2, 
Plate VIII., is from a natural size photograph of a pear that was re¬ 
ceived from Glenwood Springs, Colo., August 29. A portion of its 
surface was covered with the spore bearing projections similar to 
those on the quince. It is an uncommon occurrence, however, for 
pears to be attacked by this fungus. 
Experimenters usually agree that spraying with Bordeaux mix¬ 
ture has little effect in preventing this fungus from attacking fruit 
trees. They all recommend that the cedar and juniper trees in the 
vicinity of an orchard be destroyed, which of course is a certain 
remedy. But since orchard trees have been known to be infected 
from cedars eight miles away,* this method w T ould not be practicable 
in Colorado. The quince growing sections of the State are mostly 
in close proximity to the foot hills and mountains, the sides of which 
are covered with extensive cedar forests. * Bailey cites an instance 
in New York, however, where the rust was much less abundant in 
sprayed portions of an orchard than it was on the unsprayed trees. 
There are no records of experiments on the treatment of this 
disease in the arid regions, but since the dissemination of spores 
from cedar trees is dependent on the rain fall, it is not probable that 
the fungus will be so difficult to control as it is in humid climates. 
For this reason, also, it is not probable that the disease will be so 
abundant every year as it was last, since it is likely that a rain 
came at the time which was most favorable for the development and 
spread of the spores. 
* Bailey, L. H., Cornell Univ. Ag’l. Expt. Sta., Bulletin 80. 
