22 
The Colorado Experiment Station 
the fact that, aside from this being poor farm practice, the dangers 
from disease are increased very greatly by such a procedure. 
Little if any attention has been given either to the planting 
or the selecting of disease-free seed, with the result that we have 
built up a big seed business in a phenomenally short time, but a 
business which is destined to fail, as has been the history else¬ 
where, unless we can establish a reputation for our seed with re¬ 
spect to quality, purity and freedom from disease. 
Now is the time to do this, before our fields become generally 
infected, and while the'prevalence of disease is so slight that it can 
be controlled for the most part by the means that we have at our 
disposal. 
For the present consideration, we shall confine the discussion 
of bean diseases to those which have been observed to occur in the 
State during the last two years, and which, if neglected, may 
prove a serious menace to the industry. 
DESCRIPTION OF DISEASES 
Bacteriosis or Bacterial Blight 
Without doubt, the greatest damage to our bean crop during 
1916 resulted from an attack of the bacterial blight. This is caused 
by a germ, Pseudomonas phrseoli, which enters the plants thru 
the breathing pores or stomata and thru wounds produced by me¬ 
chanical injury. 
The disease is common upon field, garden and lima beans and 
attacks leaves, pods, stems and seed. It is very conspicuous upon the 
pods and leaves and can be recognized most easily, perhaps, upon 
the former, particularly in the wax varieties. Here we find watery 
spots ranging in size from tiny specks to areas three-eighths of an 
inch and more in diamteer. They are usually irregular in outline 
and roughly circular in shape. On the wax varieties, the spots 
are translucent or watery, amber-yellow in color and frequently 
have a rosy-red margin. Their appearance, on the whole, is not 
unlike an ordinary blister, except that they are neither raised nor 
sunken. In the more advanced stages, they may be coated over 
with a thin, pale yellow or amber-colored crust which is composed 
largely of the bacteria which produce the disease. Ulcers in all 
stages of development can usually be found on a single pod. (See 
Fig. I.) When the lesions are numerous, they frequently coalesce, 
or run together, so that the whole side of the pod presents one 
continuous canker. 
The injury to the leaves is very marked. In the early stages, 
irregular, watery spots can be found scattered over the surface 
