Rice blast

Scientific name: Pyricularia grisea, Magnaporthe grisea
Causal organism: Fungus

Host plants

Specific to rice but also infects some rice field weeds

Affected plant stages

All growth stages but the severe damage occurs during the seedling stage

Affected plant parts

All above ground parts

Symptoms

Photo source: R.K. Webster, ARS-USDA


An infected leaf has diamond-shaped or elliptical or spindle-shaped spots with gray or white centers and brown margins. The spots may merge leading to a complete drying of the infected leaf. The infected panicle turns white, causing panicle blast, and dies before being filled with grain. The infected node rots causing all above parts to die.

Conditions that favor development

1. Infested or diseased seeds
2. Excessive use of nitrogen
3. Poor air flow and poor sunlight penetration
4. Rainy days with high humidity

Prevention and control

1. Use diseased-free seeds
2. Use resistant cultivars
3. Proper plant spacing, transplanting is advisable rather than broadcasting
4. Split applications of nitrogenous fertilizer
5. Apply compost
6. Avoid farm activities when plants are wet
7. Burn diseased-straw and stubble
8. Malabar nut extract

External links

• ARS-USDA. Bolstering rice against blast. http://www.ars.usda.gov/is/AR/archive/aug04/rice0804.htm
• Rice Knowledge Bank. Rice Doctor. Rice blast. http://www.knowledgebank.irri.org/RiceDoctor/index.php?option=com_content&view=article&id=562&Itemid=2767
• WARDA. Tracking down a notorious cereal killer. http://www.warda.cgiar.org/newsletter/no%203/trackingdown.htm

References

• IRRI & Queensland University. (2001): Rice IPM. An interactive information and identification system for integrated pest management in rice. University of Queensland and IRRI.
• Reissig, W.; Heinrichs, E.; Litsinger, J.; Moody, K.; Fiedler, L.; Mew, T.; Barrion, A. (1986): Illustrated guide to integrated pest management in rice in tropical Asia. IRRI. Los Banos, Laguna, Philippines.