Bacterial wilt of brome

The causal agent of this disease is the bacterium Xanthomonas bromi. It is a highly specialized phytopathogenic bacterium that targets the vascular system of grasses. As a result of infection, the plant experiences systemic symptoms, leading to tissue chlorosis and necrosis. This pathogen is categorized within the genus Xanthomonas, known for causing various bacterial wilts in cereal and forage crops.

The primary hosts of this pathogen are various species of the genus Bromus, commonly known as brome grasses. These plants are essential components of forage landscapes and seed production fields. When an infection occurs, the physiological integrity of the host is compromised, leading to substantial economic losses in biomass yield and overall pasture productivity.

Early symptoms include the appearance of longitudinal chlorotic streaks along the leaves. As the infection progresses, these streaks evolve into brown necrotic lesions, leading to leaf wilting and eventual plant decline. In humid environments, a bacterial ooze may be visible on the surface of the infected tissue, which serves as a secondary inoculum source for further spread.

The development and spread of Xanthomonas bromi are heavily influenced by environmental factors such as high humidity, frequent rainfall, and optimal temperatures. The bacteria enter the plant through natural openings like stomata or through wounds caused by mechanical damage, including grazing or harvesting activities. Once inside, the colonization of the vascular system prevents water uptake, resulting in rapid wilting.

Effective management strategies rely on a combination of cultural and sanitary practices. Key approaches include the selection of resistant cultivars and the implementation of strict field sanitation to prevent the carryover of inoculum from one season to the next. Ensuring adequate soil fertility and balanced fertilization can also help plants withstand the stress caused by the pathogen. Regular monitoring and timely harvesting are essential to minimize the spread of the disease within the stand.