26 
The Colorado Experiment Station 
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 pheseoli, which enters the plants thru the breath¬ 
ing pores or stomata and thru wounds produced by mechanical 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 diameter. 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, ex¬ 
cept 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. 1.) 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 which 
soon turn yellow and in a short time become frosty-brown in color. 
If the spots are numerous they will often coalesce and give the dry, 
brown leaf a peculiar blistered appearance. (See Fig. II.) The 
tissue in this condition is extremely brittle and is easily torn and broken, 
which accounts for the ragged condition of blighted leaves. The 
stems are affected in much the same way as the foliage. 
Badly diseased plants lose their leaves early and fail to mature 
their seed. Spotted pods are unfit for the market as green beans, and 
seed from them is very apt to be diseased as the infection is com¬ 
municated to the seed from the pod. 
Pod-Spot or Anthracnose 
Pod-spot or Anthrocnose has been of relatively little importance 
thus far in Colorado bean fields, but because of its ravages in other 
localities, it seems advisable to become acquainted with its symptoms 
in order that it may be recognized should it become serious. 
The disease makes its first appearance on the seed-leaves and 
stems of the seedling plants. Tt manifests its presence there by 
brown, discolored, sunken spots or ulcers, indicating rather clearly that 
