22 MISC. PUBLICATION 4 4 0, U. S. DEPARTMENT OF AGRICULTURE 



so numerous or severe that the plants wilt and collapse in 5 to 6 days 

 after inoculation. These phenomena are the basis for experimental 

 work in the development of resistant strains by selection and breeding 

 for the control of anthracnose. 



CONTROL MEASURES 



The use of disease-free seed is a most satisfactory means of con- 

 trol of anthracnose. In some localities hand selection of seeds from 

 pods or from plantings free of anthracnose may be possible. The 

 seed so selected will produce a disease-free crop* if it is planted in 

 clean soil. It is usually possible and highly desirable to procure 

 seed grown in sections where climatic factors are not favorable for 

 anthracnose, such as Colorado, Idaho, and California, where a com- 

 bination of high temperatures and semiaridity or aridity exists. 



The use of resistant varieties to control anthracnose is* complicated 

 by the fact that there are several forms of the causal organism, 

 and plants resistant to one form may not be resistant to another. 

 The growers in each locality should test suitable varieties for degree 

 of resistance under their conditions. 



Precooling and good refrigeration (38° to 44° F.) in transit will 

 check the development of anthracnose infections already present in 

 beans at the shipping point and will prevent the development of new 

 infections for approximately 2 weeks. 



(See 61, 63, 64, 72, 81, 8J+, 100, 116, 117, 118, 13 % 137, 15%.) 



BACTERIAL BLIGHT AND HALO BLIGHT 



(Phytomonas phaseoli (E. F. Smith) Bergey et al., P. medicaginis var. 

 phaseolicola Burk. ) 



OCCURRENCE, SYMPTOMS, AND EFFECTS 



Bacterial blights of beans are much more common and destructive 

 than was originally thought. They are now recognized as being 

 very serious in sections where weather conditions are favorable for 

 their development and spread. 



One or more forms of bacterial blight are found in practically 

 all important bean-producing sections of the United States and of 

 Europe. This type of disease affects garden, field, and lima beans 

 of many varieties, none apparently being entirely immune, although 

 some seem to show resistance. In addition to seriously interfering 

 with germination of the seed, bacterial blights hinder the growth 

 and development of the plant. A great reduction in yield may be 

 expected in fields of beans that are badly infected, and those pods 

 that do mature may become so spotted that they are worthless by the 

 time they reach the market. Small spots that are easily overlooked 

 at shipping point may enlarge during transit and either make the 

 product worthless or reduce its market value to such an extent as to 

 make the shipping of affected beans extremely unprofitable. 



On the pods the bacterial blight is indicated by small, watery spots 

 that gradually enlarge, forming irregular blotches varying in color 

 from amber yellow to almost brick red around the margin (pi. 7, B). 

 The bacteria often ooze out of the center of the spots and show as 



