ENEMIES OF THE BEAN 



3 1 5 



Figure 336. — Bean Plant 

 Injured by Bacteria. 



229. Enemies of the Bean. — Besides this struggle to gel 

 its share of light, food, and moisture, the bean plant has 



to contend with enemies. One 



enemy is a plant or bacterium 



(Chapter XXI II) which lives 



upon the tissues of the bean. 



This bacterium causes the dis- 

 ease known as bean blight, one of 



the most destructive diseases of 



beans, and one which scientists 



have been unable to prevent or 



cure. The plants having bean 



blight appear wilted, and have 



clear watery spots in the leaves 



which, after a time, turn brown, 



dry up, and drop out, leaving a hole in the leaf where 



each spot was. The bacteria which cause the disease 



enter through the stomata, appear first in the cotyledons, 



then work into the 

 stem, and finally kill 

 the plant by stopping 



up the sap tubes. The 

 bacteria arc carried by 

 insects from one plant 

 to another. 



Any insect which 

 carries these bacteria 

 is indirectly an enemy 

 of the bean plant, hut 

 bean weevils injure it 



directly ( Figure 337 >. 



The female weevil 

 gnaws holes through the young pod and pushes her eggs 

 into the pod or into the young beans. The eggs develop 



Figure 337. — Beans Damaged by Weevils. 



