DISEASES OF CROPS 241 



BEAN 



Anthracnose (Colletotrichum lindemuthianum [Sacc. and Magn.], B. 

 and C). — This disease is most severe on the wax beans. It occurs on 

 the pods, causing unsightly, dark-colored, sunken, canker-like spots. It 

 also attacks the leaves and stems, producing similar spots and frequently 

 causing the death of the plants. The fungus is carried in the seed and one 

 diseased seed in a thousand is enough to infect a large number of growing 

 plants. 



Treatment. — Select clean seed. 



Rust (Uromyces appendiculatus [Pers.], Link). — This fungus causes 

 minute rusty spots or blisters on the under surface of the leaves and 

 occasionally on the pods. These blisters break and set free great quan- 

 tities of the reddish or rust-colored spores. It is not so severe as the 

 anthracnose. 



Treatment. — Practice clean cultivation and burn all old vines in the 

 faU. 



Blight (Pseudomonas phaseoli, Smith). — This disease attacks leaves, 

 stems and pods, causing large watery areas, which later become dry, brown 

 and papery. It is carried from year to year in the seed. 



Treatment. — Use seed from healthy plants. 



Downy Mildew (Phytophthora phaseoli, Thaxt.). — This disease is 

 unlike the mildew on the fruits. It attacks the pods of lima beans, causing 

 irregular areas of dense, woolly-white growth. It also occurs on other 

 parts of the plant, causing dwarfing and irregular growths. 



Treatment. — Spray with Bordeaux mixture. 



Leaf Spot (Phyllosticta sp.). — This disease is most severe on the pole 

 lima beans. It causes an irregular spotting of the leaves and to some 

 extent of the pods. It is carried from season to season in the seed. 



Treatment. — Spray with Bordeaux mixture. 



PEA 



Spot (Ascochyta pisi, Lib.). — This disease causes spots on stems, 

 leaves and pods which are most conspicuous on the latter. On the pods 

 they are circular, sunken with dark borders and pale centers, becoming 

 pink when mature. The spots on the leaves are oval and usually show 

 concentric circles. When severe on the stems it causes wilting and death 

 of the plant. 



Treatment. — Select clean seed and rotate crops. 



BEET 

 Leaf Spot (Cercospora beticola, Sacc). — This fungus causes the very 

 common circular, brown, purple-bordered spots with ash-colored centers. 

 Treatment. — Spraying with Bordeaux mixture will control this dis- 



