Family Leguminosae 267 



DISEASES OF THE LIMA BEAN (Phaseolus 



lunatus var. macrocarpus) 



Lima beans, whether climbing or dwarf, are usually 

 considered hardy. This is generally true under 

 favorable weather conditions. But in hot moist 

 weather, truckers may lose heavily from various 

 diseases. 



BLIGHT, see BEAN, p. 260. 



DOWNY MILDEW 

 Caused by Phytophtora phaseoli Thax. 



Perhaps the greatest damage in wet seasons to 

 lima bean culture of both the pole and the dwarf 

 varieties is downy mildew. The damage from this 

 disease equals that from the anthracnose on snap and 

 other varieties of Phaseolus vulgaris. 



Symptoms. It is most conspicuous on the pods, 

 where it forms a dense, dirty white mycelial growth 

 (fig. 48 a-c). The trouble appears first on one side 

 of the pod, and then works its way through to the 

 other side. Infected pods wilt, shrink, and eventually 

 dry up and die. In early cases of infection, the dis- 

 eased area is separated from the healthy by a purplish 

 border. Occasionally the blossoms are affected, in 

 which case they wither and drop off. On the leaves 

 the disease is manifested as irregular purplish dis- 

 coloration, especially on the veins, but there seems 

 to be no evidence of the fungus growth on it . 



