Diseases oe Beans 
25 
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 ma¬ 
ture their seed. Spotted pods are unfit for the market as green 
beans, and seed from them is very apt to be diseased as the in¬ 
fection is communicated to the seed from the pod. 
Pod-Spot or Anthracnose 
Pod-spot or Anthracnose has been of relatively little impor¬ 
tance 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. It manifests its presence there by 
brown, discolored, sunken spots or ulcers, indicating rather clearly 
that the causal fungus, Colletotrichum lindemuthianum, has been 
carried over winter in the seed. 
In due course of time, spores, by means of which the disease 
is spread, are produced in these early spots. Eventually they are 
blown, or otherwise carried, to the growing stems, leaves and pods, 
where they soon become established and begin their destruction. 
On die leaves we find reddish or blackened areas developing 
along the large veins on the under surface. The veins may be 
eaten thru by the fungus and destroyed, while the blade shows 
numerous cracks or holes with shriveled, blackened margins. 
Leaves in this condition are practically worthless as food-building 
organs, and as a result the nutrition of the plant is greatly im¬ 
paired; either the yield of seed is reduced appreciably or the seed 
fails to mature. 
Previous to the time of blossoming, the attack has been con¬ 
centrated against the leaves, and by the time the young pods make 
their appearance the fungus has become well established and is 
amply supplied with spores. These soon find their way to the 
young, tender pods where they produce rusty-brown or black 
sunken spots with reddish or yellowish margins. (See Fig. III.) 
These vary in size, much as the bacterial spots previously describ¬ 
ed. The spores of the fungus are produced in the center of the 
black ulcers and form little pink masses visible to the naked eye. 
