BLAST DISEASE OF RICE

(1)

Common Name in the Philippines:

Rice Blast – English Mata-mata – Tagalog Agupaw – Waray Taya-taya – Cebuano

Causal Organism:

Pyricularia grisea

Synonyms: Pyricularia oryzae, Magnaporthe grisea, Magnaporthe poae and Trichothecium griseum

Economic Impact in the Philippines:

 Many thousand hectares of rice fields suffer more than 50% yield losses. A 10% neck rot causes yield loss of 6%

and 5% increase in chalky kernels.

Symptoms:

Leaf blast (Seedling to tillering stage)

 Small to spindle-shaped spots with brown border and gray center.

 Spots join resulting in drying and death of leaves.

Node blast/Collar blast (Tillering stage)

 Black, rotten node that later breaks.

Panicle blast (Booting to heading)

 Black and later breaks.

 Unfilled panicle.

Seeds (Maturity)

 Sterile lemma and rachilla discolored with fungal growth.

Mode of Transmission:

IRRI, (2003)

Factors of Development:

 Presence of the blast spores in the air throughout the year

 Upland rice environment

 Cloudy skies, frequent rain, and drizzles

 High nitrogen levels

 High relative humidity and wet leaves

 Growing rice in aerobic soil in wetlands where drought stress is prevalent

Management Options:

Cultural

 Planting resistant varieties.

 Early sowing of disease-free seeds after the onset of the rainy season. Water seeding is better than drill seeding.

 Proper plant spacing. Transplanting is advisable than broadcasting.

 Avoid excessive use of fertilizer. Nitrogen should be applied in small increments at any time. Nitrate nitrogen is more conducive to disease development than ammonium nitrogen.

 Water management practices in rainfed areas lessen the likelihood of stress.

 Avoid farm activities when plants are wet.

 Destruction of diseased crop residue by burning.

Chemical

 Fungicides such as benomyl, pyroquilon and tricyclazone are possible chemicals for controlling the disease. Two applications is recommended – one at early heading and a second a few days later when the heads are most of the way out of the boot.

International Rice Research Institute (IRRI). 2003. Rice Knowledge Bank Version 2.2., Los Baños, Laguna, Philippines.

Philippine Rice Research Institute (PhilRice). 2002. Field Manual on Major Disorders of Rice Plant in the Philippines (Pathological and Nutritional).

Science City of Muñoz, Nueva Ecija, Philippines.

Popular varieties susceptible…:Growers watch for blast in rice crop. 2002.

Delta Farm Press

SCScardaci, et al. 1997. Rice blast: A new disease in California. Agronomy fact sheet series. Dept of Agronomy and Range Science. University of California, Davis.

www.oisat.org and www.CNWInfo.com Node blast/Collar blast

Leaf blast Panicle blast

For further inquiries, please contact the Crop Protection Division, PhilRice, Maligaya, Science City of Munoz 3119, Nueva Ecija Tel. No. (044)456-0285, -0258, -0277 local 227