Not known to transmit any human or animal pathogens.

No known vector.

Bacterial streaming from rice leaf tissue or germinated seedlings can be a preliminary indication of infection. However, bacterial streaming is not X. oryzae-specific and can be caused by saprophytic bacteria

Symptoms caused by Xanthomonas oryzae pv. oryzae (bacterial blight (BB)) and Xanthomonas oryzae pv. oryzicola (bacterial leaf streak (BLS)) are easily differentiated in the early stages of disease but can appear similar in later stages. For BB, look for symptoms in the tillering stage (the end of the seedling stage when the fourth true leaf emerges), and for BLS, symptoms can appear at any stage of growth.

X. oryzae pv. oryzae: Symptoms of BB include water-soaked spots at the leaf margins that increase in size, becoming elongated lesions that turn yellow and then necrotic. Leaf wilting and rolling may occur. Another symptom known as kresek occurs from the seedling to the early tillering stage, often 1 to 2 weeks after transplanting. Leaves of infected plants wilt, roll, and become grayish green in color. These leaves then turn yellow to straw-colored and wither. The entire plant generally dies, but plants that do survive are stunted and yellow in color. Total crop failure is not uncommon with kresek.

Signs of BB include drops of bacterial exudates (ooze) that may form on young lesions about 8 to 10 days after infection. This ooze may dry to form small, yellow beads. Bacteria may also ooze out from hydathodes (water pores). Rice seed may be discolored and poorly filled. 

X. oryzae pv. oryzicola: Symptoms of BLS initially appear as small, interveinal, water-soaked streaks. The streaks are dark green at first and later become translucent. Eventually, the entire leaf turns brown, then grayish-white and dies.

Signs of BLS include bacterial ooze that may develop on the surface of lesions. This ooze may dry to form small, yellow beads.

Survey throughout the growing season, based on the timing of external symptom appearance and the availability of resources. Bacterial blight appears only during the tillering stage, and bacterial leaf streak can infect rice at any stage but is most visible at maximum tillering.

Surveyors should visually examine rice plants for signs/symptoms and collect symptomatic (or asymptomatic, if necessary) leaf tissue samples for further diagnostic identification. 

Survey for X. oryzae in rice fields, especially those in areas of high rice production with climatic regions conducive to the establishment and spread of the pathogen. 

Collect symptomatic leaf tissue. Asymptomatic tissue can be sampled if symptomatic tissue is not found. Place samples from each plant in a plastic bag and seal. Do not add extra moisture to the bag. Label the sealed bag with the host species/cultivar and the symptoms observed during collection. Place the bag into a secondary plastic bag and seal. Keep double-bagged samples in a cooler with ice in the field and then refrigerate as soon as possible. 

Between sampling sites, wash off any dirt and debris, then sanitize all tools, equipment (vehicles/tires, bucket lifts, ladders, etc.), and footwear with a 10 percent bleach solution, 1-part bleach (any commercial bleach) to 9-parts water. Immerse the cutting portion of the tool(s) in bleach for at least 10 minutes and then allow to air-dry to prevent the spread of the pathogen. For tools and equipment that cannot be immersed, thoroughly spray with bleach and allow the bleach solution to remain wet on surfaces for at least 10 minutes. 

Identification based on morphology may not be reliable due to the prevalence of "look-alike" species on rice seed. Preliminary screening of Xanthomonas oryzae can be accomplished through semi-selective media followed by classical biochemical tests, serological tests, or PCR detection. Examples include:

• Lang et al. (2010) provides multiplex PCR primer sequences for X. oryzae pv. oryzae and X. oryzae pv. oryzicola. 
• Lang et al. (2014) provides primer sequences for detection of X. oryzae pv. oryzae and X. oryzae pv. oryzicola using Loop Mediated Isothermal Amplification (LAMP) technology. 
• An Enzyme Linked Immunosorbent Assay (ELISA) test kit for X. oryzae pv. oryzae is commercially available from Agdia, Inc. 
• Selective media and biochemical assay protocols for Xanthomonas oryzae can be found in Schaad (1981).

Bacterial leaf blight of rice caused by Pantoea agglomerans, P. ananatis, P. dispersa, P. stewartii, and P. wallisii cannot be differentiated from BB based on visible symptoms. Pantoea agglomerans, P. ananatis, and P. stewartia are present in the United States, but only P. ananatis has been found in rice.

Cercospora janseana, causal agent of narrow brown leaf spot, is a fungal pathogen found on rice in the United States that produces symptoms similar to BLS.