BEAN ANTHRACNOSE 
This is one of the most serious diseases with which the vegetable- 
gardener has tocontend. It occurs wherever beans are grown and, under 
conditions favorable for the fungus, will ruin an entire crop. 
SYMPTOMS 
Lesions are found on all parts of the plant above the root. 
On the seedlings provided, OBSERVE :— ; 
1. The elongated, blackened lesions on the stems, with the 
centers shrunken and in some cases the host-tissue cracked open. 
2. The lesions on the cotyledons which resemble very much 
those on the pods. Where do the lesions first appear, on the stem or on the 
cotyledon? Why? 
Make a DRAWING of a diseased seedling. 
On the leaves provided, OBSERVE :-— 
3. The browned or blackened lesion on the under side. The 
areas between the veins are seldom injured. On the young growing leaves 
the veins are often killed while the tissues between still continue to grow, 
so that the leaf becomes distorted. Do the lesions show on the upper side 
of the leaf? DRAW. 
On the pods provided, OBSERVE :— 
4. The distinct regularly outlined, much depressed spots on the 
pod; their shape and size. 
5. The margin of each, bordered with a red zone, and that 
where two spots are near together, the red zones coalesce. 
6. The blackened center and, occasionally in the larger lesions, 
the host-tissue so shrunken that it is cracked open. Are there any spots 
lacking the black centers? 
Make prawincs of several lesions on a pod to show the above points. 
On the seeds provided, OBSERVE :— 
7. The browned or blackened areas. Do they resemble in any 
way those on the pods? Are they depressed? Is the seed-coat ruptured 
at any point in the lesion? DRAW. 
Compare the symptoms of this disease with those of bean blight, shown 
in the illustration materials. 
ETIOLOGY 
The pathogene causing bean anthracnose is Colletotrichum Linde- 
muthtanum (Saccardo and Magnus) Briosi and Cavara. It is one of the 
Melanconiales, a group of the Fungi Imperfecti. Its perfect form is not 
known but is doubtless an ascomycete of the genus Glomerella. 
Life-history. ‘ 
The Primary Cycle is initiated by conidia from the lesions on the 
cotyledons. When diseased beans are planted they contain mycelium 
of the pathogene, which at the germination of the host also begins to grow 
and is ready to produce spores when the cotyledons push above the surface 
of the soil. ; 
Pathogenesis. Scrape some material from a lesion on the cotyledon 
of a seedling provided. Mount and examine. oBSERVE:— 
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