Rice Diseases in the Philippines: A Guide by Growth Stage

Farmers know many of these by local names. Blast is mata mata in Bisaya, agupaw in Waray and taya taya among Cebuano speakers in Mindanao. Sheath blight is masot in Pangasinan. Grassy stunt and ragged stunt share the Tagalog name burit.

Rice diseases by growth stage

Each disease has a stage when the crop is most at risk. Scout for the right one at the right time.

Not sure what you are looking at? Take a clear photo of the leaf in daylight and ask Anee, the smart farm technician in anee.io. She answers in Tagalog or English, and she checks your lot's growth stage before she replies.

The big rice diseases, one by one

Blast

Rice blast comes from the fungus Magnaporthe oryzae and can hit the leaf, collar, node and neck. Leaf spots are spindle shaped, with gray centers and brown borders. If the neck rots before the milky stage, no grain forms. High nitrogen, long dew, light rain and water stress all favor it. So put resistant varieties first, then moderate, split nitrogen and no water stress.

Bacterial leaf blight

Bacterial leaf blight comes from Xanthomonas oryzae pv. oryzae. On seedlings it causes kresek, a wilt that kills the whole plant. On older rice, yellow stripes with wavy edges run down from the leaf tip. Milky drops of ooze show in the early morning. Strong wind and heavy rain spread it, while excess nitrogen and a lack of phosphorus and potassium make it worse.

Tungro and the stunt viruses

Tungro is two viruses carried by the green leafhopper. Leaves turn yellow to orange from the tip down, plants stay short, and sick hills show up in clusters that grow. It does not travel in seed.

Grassy stunt and ragged stunt ride with the brown planthopper. Grassy stunt makes an upright, grassy tuft of many tillers. Ragged stunt leaves torn, twisted leaves on a plant that stays dark green. Once a rice plant has the virus, nothing can cure it yet.

Sheath blight

Sheath blight, from the fungus Rhizoctonia solani, starts as oval greenish gray spots on the sheath just above the water. In dense, heavily fertilized palay it climbs to the leaves and spreads to the next hill. Its hard resting bodies, the sclerotia, survive in the soil for months and float on the water. No resistant variety is available yet. So wider spacing, moderate nitrogen and a few days of draining at maximum tillering do the work.

Brown spot, false smut and bakanae

Brown spot makes round brown spots with gray centers. It is tied to poor, unflooded soil and to potassium deficiency, so fix the soil first.

False smut turns single grains into velvety balls, orange at first and greenish black later. Rain, high humidity and high nitrogen favor it. Bakanae is seedborne. Infected seedlings grow tall, thin and pale, then die or give empty grains.

Resistant varieties are the first defense

A resistant variety is the top choice against blast, bacterial leaf blight, tungro, grassy stunt and ragged stunt. It is the cheapest, most reliable control for bacterial leaf blight. Examples are PSB Rc10 for blast, Rc 242 for bacterial leaf blight and Rc 120 for tungro.

Resistance works disease by disease, though. In trials, the hybrid Mestiso 19 (NSIC Rc202H) withstood tungro, yet it was susceptible to bacterial leaf blight. So pick a variety that resists the diseases your farm had before. New ones come out every year, so ask your local agriculture office for the current list.

anee.io can help with that search. In Variety Ranking, Anee looks up the newest Philippine varieties of your crop and their resistance ratings. Then she compares them for your field and season.

Clean seed, balanced nitrogen and good water

Timing is everything here. The anee.io cropping calendar dates every task from each lot's own day zero. So the nitrogen splits, the drain and the scouting walks land on the right day. The growth stages view also lists what to watch for at each stage.

When a fungicide makes sense

A fungicide is the last step, never the first. It does nothing against tungro, grassy stunt or ragged stunt, because those are viruses. Chemicals against bacterial leaf blight are not economical or effective either. For the fungal diseases, spray only when scouting and the weather show real risk.

• Blast. Triazoles (FRAC group 3) and strobilurins (FRAC group 11) can be used with care. One spray at heading can pay where the risk of yield loss is high.
• Sheath blight. If you spray, aim at the leaf sheaths between stem elongation and booting.
• Brown spot and bakanae. Treat the seed, not the field. Propiconazole (group 3) and azoxystrobin (group 11) are among the brown spot seed treatments. The bakanae fungus also builds resistance to repeated benomyl (group 1).
• False smut. No spray is recommended. Keep the field clean, use moderate nitrogen and plant certified seed.

Rotate groups between sprays, because products with the same FRAC number share one weak point. Our fungicide guide explains the groups, and the overview of plant diseases in the Philippines lists the common ones.

Questions about rice diseases