Bacterial blight of cotton (also called angular leaf spot) is an important and potentially destructive bacterial disease. The disease is caused by a bacterium, Xanthomonas campestris pv. malvacearum. Cotton yield losses in excess of 10% have been reported in the past, although significant losses to this disease in the United States have not been reported in many years. The disease has only been detected sporadically in North Carolina.
Bacterial blight starts out as angular leaf spot with a red to brown border (Figure 1). The angular appearance is due to restriction of the lesion by fine veins of the cotton leaf. Spots on infected leaves may spread along the major leaf veins. As disease progresses, leaf petioles and stems may become infected resulting in premature defoliation (cotton black leg, Figure 2). Black cankers may girdle the stem or branches causing the portions to die above the canker. A white waxy crust containing the bacterium may form on old leaf spots or cankers. Bolls may become infected causing boll rot which results in rotted seed and discolored lint. Infected bolls have round, rather than angular, lesions that initially may appear water-soaked. As infection proceeds, bolls lesions will be sunken and dark brown or black.
The extent to which bacterial blight will impact cotton yield in infested fields will depend on environmental conditions during the season. High rainfall, and humidity as well as warm temperatures favor disease development. Yield losses of greater than 10% have been reported.
in furtherance of the acts of Congress of May 8 and June 30, 1914.
North Carolina State University and North Carolina A&T State University
commit themselves to positive action to secure equal opportunity regardless
of race, color, creed, national origin, religion, sex, age, or disability.
In addition, the two Universities welcome all persons without regard
to sexual orientation. North Carolina State University, North Carolina
A&T State University, U.S. Department of Agriculture, and local