20 MISC. PUBLICATION 440, U. S. DEPARTMENT OF AGRICULTURE 



leaves the vitality of the plants may be so reduced that few or no 

 marketable pods are produced. 



On the leaves small angular brown spots closely crowded to- 

 gether are produced; on the pods the spots vary greatly in size and 

 are characterized by two distinct zones of color, the reddish-brown 

 center of each spot being sharply separated from an outer black 

 zone, which in turn is clearly separated from the healtlry portions 

 of the pod. Black bundles of spore-bearing mycelium often cover 

 the surfaces of the lesions, giving a characteristic appearance to the 

 larger spots. 



No means of control are known. 



(See 93.) 



ANTHRACNOSE 



(Colletotrichum Hndemuthianum (Sacc. and Magn.) Briosi and Cav.) 



OCCURRENCE, SYMPTOMS, AND EFFECTS 



Anthracnose occurs in varying degrees on varieties of wax, green 

 pod, pole, navy, and kidney beans, and on some varieties of other 

 species, such as the scarlet runner and the lima bean. 6 



The disease is world-wide in its distribution. Whether or not it 

 will occur in a given locality or during a given season is determined 

 primarily by climatic conditions. Moderately cool, humid or rainy 

 weather during the early part of the growing season is essential 

 for the development of anthracnose in serious form. 



From the point of view of production, the losses are due to poor 

 germination of affected seed, to destruction of diseased seedlings, and 

 to low yields of affected plants. In marketing, the losses are due 

 to spotting of the pods, which renders them unsightly and unsalable 

 for table and canning purposes. The spotting may appear on the 

 pods before or after picking and frequently develops in transit on 

 pods that appeared healthy when packed. Sometimes the fungus 

 penetrates the pod to the seed and causes a spotting, which lowers 

 the selling price of the dry seed. 



On the pods, the first symptoms are minute oval or circular greenish- 

 brown specks, which later become brick or rust red to black around 

 the border as they enlarge (pi. 7, A). These spots may range in size 

 from mere specks to areas one-half inch in diameter. As the spots 

 enlarge their centers sink and become dark. Under moist condi- 

 tions, the center becomes covered with flesh-colored dots, which are 

 heaps of fungus spores, and these sometimes run together forming 

 a slimy layer. Under dry conditions, the spore masses dry down to 

 gray, brown, or even black granulations, or to small pimples. 



In the case of early infections, the fungus often grows from the 

 pod wall into the seed. When the attack is light, the seed shows only 

 yellowish spots, but when severe, the spots may have yellow, brown, 

 or even black centers with tawny-brown or tan-colored borders. The 

 lesions may occur anywhere on the seed. 



8 An anthracnose caused by Oolletotrichum truncatum (SHiw.) Andrus and Monro injures 

 i in- lima and garden beans to some extent in the Southeastern states. Small, red super 

 flclal blotches are the first symptom on the pods. Later the blotches may spread ami 

 become brown or grayish and show numerous black fruiting bodies that look like pycnidla. 

 This type of anthracnose apparently is not yet a market factor. 



