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This is a factsheet from IRRI http://www.knowledgebank.irri.org/decision-tools/rice-doctor/rice-doctor-fact-sheets/item/bacterial-blight. It was copied here on December 20th 2018
The content experts are CM Vera Cruz (email: firstname.lastname@example.org), I Ona, NP Castilla, and R Opulencia
Bacterial blight is caused by Xanthomonas oryzae pv. oryzae.
It causes wilting of seedlings and yellowing and drying of leaves.
The disease is most likely to develop in areas that have weeds and stubbles of infected plants. It can occur in both tropical and temperate environments, particularly in irrigated and rainfed lowland areas. In general, the disease favors temperatures at 25−34°C, with relative humidity above 70%.
It is commonly observed when strong winds and continuous heavy rains occur, allowing the disease-causing bacteria to easily spread through ooze droplets on lesions of infected plants.
Bacterial blight can be severe in susceptible rice varieties under high nitrogen fertilization.
Check for wilting and yellowing of leaves, or wilting of seedlings (also called kresek).
On seedlings, infected leaves turn grayish green and roll up. As the disease progresses, the leaves turn yellow to straw-colored and wilt, leading whole seedlings to dry up and die.
Kresek on seedlings may sometimes be confused with early rice stem borer damage.
To distinguish kresek symptoms from stem borer damage, squeeze the lower end of infected seedlings between the fingers. Kresek symptoms should show yellowish bacterial ooze coming out of the cut ends. Unlike plants infested with stem borer, rice plants with kresek are not easily pulled out from soil.
Check for lesions:
To quickly diagnose bacterial blight on leaf:
Bacterial blight is one of the most serious diseases of rice. The earlier the disease occurs, the higher the yield loss.
Yield loss due to bacterial blight can be as much as 70% when susceptible varieties are grown, in environments favorable to the disease.
When plants are infected at booting stage, bacterial blight does not affect yield but results in poor quality grains and a high proportion of broken kernels.
Planting resistant varieties has been proven to be the most efficient, most reliable, and cheapest way to control bacterial blight.
Other disease control options include: