PLANT DISEASES DUE TO FUNGI. 



53 



BEAN ANTHRACNOSE. 



Colletotrichum lindetnuthianum (Sacc. and Mag.). 



During the past year very serious losses have 

 been occasioned to scarlet runners and French 

 beans by the disease known as Anthracnose, 

 Bean Pod Canker, and Pod Spot, and as no 

 adequate account has been given of the disease 

 in this country, it is here treated of at some 

 length. 



Whetzel 1 has shown that the disease is due 

 to a fungus which lives as a parasite in the 

 plant tissues. The first appearance of the fungus 

 is on the seedlings, and appears as brownish - 

 coloured spots or pit-like spots on both seed- 

 leaves and stem. In some cases the stem is so 

 badly attacked at its base with pitted spots, that 

 the young plants fall over and die. Later, on 

 each of these spots, spores are produced, and 

 these are carried on to the leaves and stems of 

 the plants. In bad attacks the leaves are eaten 

 through, and irregular cracks or holes, with 

 blackened margins, appear. 



At a still later date after the fungus has 

 established itself upon the stems and leaves, it 

 spreads to the pods. Each spore that falls upon 

 the pod, in the presence of moisture and a suit- 

 able temperature, develops a minute germ-tube, 

 which enters into the tissue of the pod (Fig. 

 26), and commences to branch and feed upon 

 the tissues of the plant. The characteristic 

 rusty brown spots now appear as pit -like 



spots, and here more spores are formed (Fig. 25). These are piled 



up in minute pinkish masses and held together by a sticky secretion. 



A drop of rain or dew is sufficient to dissolve this mucilage and set 



free the spores. 



As the pods develop the mycelium of the fungus penetrates deeper 



FIG. 23 BEAN 



ANTHRACNOSE. 



Pods shewing canker. 



1 Cornell Univ. Agric. Exp. Stat., Bull. 239, 1906. 



