Diseases of Sorghum 
(Sorghum bie%r (L.) 
Moench) 

___ BACTERIAL CAUSES __ _ 

Bacterial Leaf Spot 

This disease is also called bacterial spot. 

CAUSE: Pseudomonas syringae pv. syringae van Hall (syn. P. syringae 
van Hall) overwinters in soil and on seed. It probably also survives on 
infected residue, Johnsongrass, and on sorghum plants remaining after 
harvest. Bacteria are disseminated by wind, rain, and insects. Infection 
occurs through stomates and wounds. Disease development is favored by 
wet, cool weather (12°C optimum). 

DISTRIBUTION: Generally distributed wherever sorghum is grown. 

SYMPTOMS: Spots first appear on lower leaves with infection moving 
up the plants as they approach maturity. Spots are circular to elliptical 
and 1-10 mm in diameter. Initially spots are dark green and water­
soaked but soon become tan with a red border. Small lesions may be 
entirely red with somewhat sunken centers. Sometimes spots are so 
numerous that they coalesce to form large diseased areas, resulting in 
the death of the whole leaf. Lesions may also occur on leaf sheaths and 
seeds. 

CONTROL: 
1. Plant healthy seed that has been treated with a seed-protectant 

fungicide. 

465 R. F. Nyvall, Field Crop Diseases Handbook
© Springer Science+Business Media New York 1989



466 DISEASES OF SORGHUM (SORGHUM B/COLOR (L.) MOENCH) 

2. Rotate sorghum with non susceptible crops. 
3. Plow under infected residue where soil erosion is not a problem. 
4. Destroy Johnsongrass and any sorghum plants left after harvest. 

Bacterial Leaf Streak 

This disease is also called bacterial streak. 

CAUSE: Xanthomonas campestris pv. holcicola (Elliott) Dye (syn. 
x. holcicola (Elliott)) overwinters in residue and plants left standing 
after harvest. Bacteria are locally disseminated by water and wind. 
Dissemination over a long distance is by infected residue and seed. 
Disease development is favored by warm, wet weather. 

DISTRIBUTION: Argentina, Australia, India, Mexico, Nigeria, New 
Zealand, Philippines, South Africa, the United States, and the USSR. 

SYMPTOMS: Streaks occur on leaves of plants of all ages as water­
soaked and translucent, about 3 mm wide and 25-150 mm long. Initially 
only light yellow drops of bacterial exudate are present on the translu­
cent streaks. This will eventually dry to thin white or cream-colored 
scales. Later, red-brown blotches appear that eventually enlarge and 
become red throughout the streak, causing the water-soaked and translu­
cent areas to disappear. Portions of the streaks may broaden into elon­
gated oval spots with tan centers and narrow red margins. Numerous 
streaks may join to form long, irregular areas that cover a large area of 
the leaf with necrotic tissue bordered by dark narrow margins between 
the red-brown streaks. 

CONTROL: 
1. Rotate sorghum with other crops. 
2. Plow under infected residue where erosion is not a problem. 
3. Plant healthy seed that has been treated with a fungicide. 

Bacterial Leaf Stripe 

This disease is also called bacterial stripe. 

CAUSE: Pseudomonas andropogonis (Smith) Stapp is seedborne and 
survives in residue, soil, and on sorghum plants remaining in the field 
after harvest. Local dissemination is by wind, water, and insects. Long­
range dissemination is by infested seed or residue. Infection occurs 
through stomates and injuries caused by wind and insects. Disease devel­
opment is favored by warm (25-29°C), wet weather such as the cloudy, 
humid days following rain.