activity. It is attractive to insects, and they by their fre- 
quent visits disseminates the organisms rapidly at a period 
when the opportunities for their easy access to healthy 
plants are best. 
HOW THE GERMS GET INTO THE TREE. 
Now as to the method of gaining access to the tree. 
The virus of the disease spread upon healthy bark will not 
communicate the disease; this has often been proved by ex- 
periment. The microbe is incapable of penetrating healthy 
bark; but prick the bark with a fine needle smeared with the 
virus and you can produce the disease. The puncture or 
wound, no matter how small, is large enough to afford ac- 
cess to the germs which at once find themselves under con- 
ditions that will promote their growth. Wounds in the 
bark then, afford one means of access to the disease. Most 
cases of blight on the body of the tree originate in this way, 
certainly all those that show only isolated diseased areas, 
and in many of these cases the fact that the disease has 
spread from a central point of infection is very apparent. 
Last season portions of the trunks of several trees, ranging 
from one and one-half inches to two and one-half inches in 
diameter were sent us from an orchard near Canon City. 
Each piece bore from one to four elliptical areas of bark 
dead from blight, and in each case it was very plain that the 
disease had spread from a center; the center being a point 
where a starting shoot had been rubbed off. This would 
point to a need for some application following the removal 
of adventitious shoots to prevent the access of the blight 
organisms. 
During the winter season, fully formed bark envelops 
the whole tree, forming an impervious protective against 
the disease, so at this season the only means of access would 
be by wounds. But as the buds push in spring we have pre- 
sented other vulnerable points. The young shoots are soft 
and succulent, they have no covering capable of resisting 
attack, as has been often demonstrated. When the flowers 
expand we find in the flower cup, parts that are even less 
protected than are the youngest shoots. The stigma and 
nectaries offer conditions most favorable to the develop- 
ment of the organism. 
Insects are no doubt responsible for the first infection, 
and in their busy flight from one flower to another during 
the whole period of flowering they disseminate the disease 
from one tree to another, and from orchard to orchard. It 
has always been observed of the disease that the twig-blight 
