862 
Journal of Agricultural Research 
Vol. XXXI, No. 9 
CONTROL 
Since the disease is seed borne in the case of cowpeas, prevention 
of it would primarily require the use of disease-free seed. Disease- 
free seed can be obtained in small quantities by seed selection from 
disease-free pods. The use of two or three year old seed should 
result in decreased primary infection. 
In 1924 the disease was found on volunteer plants in a plot that was 
in cowpeas the year before. Therefore crop rotation would seem 
advisable. 
SUMMARY 
Bacterial spot of cowpea is characterized by reddish-brown lesions 
on the leaves, stems, pods, and seeds. 
The hosts include all varieties of cowpea tested, catjang, hyacinth 
bean, asparagus bean, adsuki bean, velvet bean, lima bean, bush 
lima bean, dwarf sieva bean, and the common weed, tick trefoil. 
Henderson’s Bush Lima bean has shown some resistance. 
On cowpeas the young growing organs are most susceptible, and 
infection of such organs results in considerable distortion and shat¬ 
tering of the leaves, deformity of the pods, and discoloration and 
stunting of the seeds. In seedlings and young leaves localized 
vascular infection and localized wilting may occur. 
The causal organism is a motile rod bearing one to five flagella at 
one or both poles, first described as Bacterium vignae n. sp. It is 
identical with Bacterium viridifaciens n. sp. described by Tisdale and 
Williamson. 
The colonies on agar are grayish white and, in transmitted light, 
slightly fluorescent. Gelatin is liquefied. 
Acid is produced only with dextrose and saccharose. Greenish 
pigment formation occurs in milk, alkaline broth, and in Fermi’s and 
Uschinsky’s solutions. 
Atomizer inoculation without wounds is successful. The invasion 
in cowpea leaves is intercellular, and the mesophyll is most extensively 
involved. Vein tissues are preferred and vascular invasion may 
occur in seedlings and young leaves. Epicotyl lesions may be 
accompanied by hypertrophy and hyperplasia of the underlying 
cortical or pith cells. 
Cowpea-pod infection results in seed infection. Seeds from in¬ 
fected pods gave rise to infected seedlings when planted in sterilized 
soil. Commercial seed of a number of cowpea varieties planted in 
sterilized soil also gave rise to infected seedlings. Similar seed 
stored an extra year seemed to be comparatively free from infection. 
As control measures with cowpeas, the selection of seed from 
disease-free pods, or the use of seed two or three years old, and crop 
rotation are suggested. 
LITERATURE CITED 
(1) Bailey, L. H. 
1924. manual of cultiyated plants. 851 p., illus. New York and 
London. 
(2) Buchanan, R. E. 
1918. STUDIES IN THE NOMENCLATURE AND CLASSIFICATION OF THE BAC¬ 
TERIA. V. SUBGROUPS AND GENERA OF THE BACTERIACEAE. 
Jour. Bact. 3: 27-61. 
(3) Burkholder, W. H. 
1924. VARIETAL SUSCEPTIBILITY AMONG BEANS TO THE BACTERIAL BLIGHT. 
Phytopathology 14: 1-7, 
