Rice blast, caused by the fungus Magnaporthe oryzae, infects rice plants worldwide and can destroy enough rice to feed over 60 million people. It causes lesions on leaves, collars, and panicles. High humidity and temperatures between 77-82°F favor the disease. Biocontrol methods include the fungi Aspergillus niger and Trichoderma harzianum and bacteria like Streptomyces, which can inhibit the growth of M. oryzae. Management strategies involve using certified seed, crop rotation, resistant varieties, and maintaining proper flooding and nutrition levels for rice.

1. Rice Blast
Magnaporthe grisea

2. Pathogen
• Magnaporthe oryzae or rice blast fungus, causes rice blast
• Members of the Magnaporthe grisea complex also infect other
agriculturally important cereals
• Estimated to destroy enough rice to feed more than 60 million people
• The fungus is known to occur in 85 countries worldwide

3. Symptoms and Signs
• Symptoms can occur on different parts of the plant
• Leaf blast
• Diamond-shape lesions on the leaves
• Characteristic for the quick identification of the disease in the field

5. Cont.
• Collar rot
• Infection on the plant’s neck causes rot
• Can result in a lack of seed filling or collapse of the entire panicle
• The pedicels are infected, seeds may not be produced at all

6. Ecology and
Spread
Infected grasses
Crop residues
Infected seed can be
a source of inoculum

7. Disease cycle
Pathogen infects as a
spore that produces
lesions or spots on parts of
the rice plant such as the
leaf, leaf collar and panicle
Using a structure called
an appressorium, the
pathogen penetrates
Sporulates from the
diseased rice tissue to be
dispersed as
conidiophores
Cycle complete in a week
under favorable conditions
lesion can generate up to
thousands of spores in a
single night.

8. Environment
Long periods of free
moisture where leaf
wetness is required
for infection
High humidity is
high
High relative
humidity and at 77-
82 F
Excessive amount
of nitrogen
fertilization
Drought stress
increase rice
susceptibility to the
pathogen
Extended drain
periods also favor
infection

9. BioControl
• Aspergillus niger (Fungus)
• Trichoderma harzianum (Fungus)
• Streptomyces

10. Streptomyces
• S. vinaceusdrappus
• Inhibited the mycelial growth of M. oryzae by 53.5%
• Streptomyces philanthi
• In Southern Thailand exhibited significant antifungal activity
against M. oryzae (88.73% inhibition of mycelial growth)
Boukaew and Prasertsan (2014)

11. Aspergillus niger
• In the dual culture, 81.32% inhibition percentage of M. oryzae
• pH at level 5.0 and temperature between 21℃ to 29℃ is the optimum
condition for A. niger to produce efficient antifungal metabolites
• Antifungal Metabolites
Oleic Acid, n-Hexadecanoic acid, Hexose, Glycerol, Stearic acid,
Tetradecanoic acid, Dodecanoic acid
(Idan, A. , Sijam, K. , Kadir, J. , Rashid, T. , Awla, H. and Alsultan, W. (2017)

12. Trichoderma
harzianum
Treatment of cultivar with Trichoderma harzianum
Treated seed of rice showed range of mean performance
of seed germination from 86.67 to 96.67%
Trichoderma have positive response on the seed
germination
Reduce the intensity of blast disease of rice
It can be used as effective bio-control measure for rice
blast besides increasing the yield of rice crop
Mathivanan et. al.2006.

13. Management
• Certified seed
• pre-treat seed with hot water or fungicides
• Use of resistant varieties
• Susceptible variety once

14. Cont.
• Proper sanitation measures to reduce inoculum
• Carry out crop rotation, intercropping
• Modify plant density to avoid close spacing
• Provide a balanced nutrition to the rice crop
• Maintain proper flood level for rice to grow