A disease of rice caused by the bacteria Xanthomonas campestris pv. oryzae. The leaf stage of BLB is the most widespread and, therefore, causes the most damage. The early symptoms include yellow, undulating lesions along the margins of the upper portion of the leaf blades. The lesions develop rapidly parallel to the veins and extend laterally to the healthy regions. In extreme cases, a large portion of the entire leaf blade becomes infected, turns yellow or dirty white, and finally dies.