Rice Farming Guide

What you will see

Diamond-shaped or spindle-shaped lesions on leaves with gray or white centers and brown borders. Severe leaf blast makes the field look "burned." Neck blast causes dark brown-black lesions at the panicle base, often breaking the neck and causing the panicle to droop (called "broken neck").

Conditions that favor it

Cool nights (20-25°C), high humidity above 90%, heavy dew, and excessive nitrogen fertilization. Upland rice and areas with intermittent flooding are most vulnerable.

What you will see

Wilting of seedlings (kresek phase) or yellow-to-white lesions starting from leaf tips and margins, spreading inward in wavy patterns. Infected leaves look like they have been dipped in bleach from the tip. Bacterial ooze (milky droplets) visible on leaf surface in early morning.

Conditions that favor it

Warm temperatures (25-34°C), high humidity, frequent rain, and strong winds that create wounds for bacterial entry. Spreads through irrigation water. Worst after typhoons and storms.

What you will see

Oval or irregularly shaped lesions on the leaf sheath near the waterline, initially green-gray then turning white with brown borders. Lesions enlarge and merge, spreading upward from tiller to tiller, eventually reaching leaves and causing entire tillers to collapse.

Conditions that favor it

High planting density, excessive nitrogen, warm temperatures (28-32°C), and high humidity. Dense canopy with poor air circulation. Favored by continuous flooding.

What you will see

Oval brown spots with gray centers on leaves, sometimes resembling sesame seeds scattered on the leaf. Spots also appear on glumes, causing grain discoloration and "dirty" looking harvested grain. Associated with nutrient-deficient and stressed plants.

Conditions that favor it

Nutrient-deficient soils, especially low potassium and silicon. Drought stress followed by rewetting. Often a sign of poor soil health rather than weather conditions alone.

What you will see

Stunted plants with yellow-orange leaves starting from older leaves. Discoloration appears interveinal — between the veins. Plants are significantly shorter than healthy neighbors. Grains are unfilled or poorly filled. Field shows scattered patches of discolored plants.

Conditions that favor it

Transmitted by green leafhopper (Nephotettix virescens). Both viruses must be present for full symptom expression. Most damaging in tropical lowland rice during wet season.

Damage

Larvae bore into stems, causing "deadhearts" during vegetative stage (central leaf dies and can be pulled out) and "whiteheads" during reproductive stage (panicle turns white and produces no grain). A single larva can destroy an entire tiller.

How to identify

Adult moths are straw-colored (yellow stem borer) or have a row of dark spots (striped stem borer). Check for small round holes in stems and frass (sawdust-like excrement). Pull tillers gently — deadhearts come out easily. Threshold: 5% deadhearts or 2% whiteheads.

Damage

Sucks sap from the base of rice plants, causing "hopper burn" — large circular patches in the field where plants turn brown and collapse. Massive outbreaks can destroy entire fields within days. Also transmits grassy stunt and ragged stunt viruses.

How to identify

Small (4-5mm), brown, wedge-shaped insects found at the base of tillers at or below the waterline. Part the tillers and check the stem base. Fields with hopper burn show a characteristic circular pattern spreading outward. Threshold: 10 BPH per hill.

Damage

Larvae fold leaves lengthwise by spinning silk threads, then feed inside the fold by scraping the green tissue, leaving transparent white streaks. Heavy infestations give the field a whitish, "scorched" appearance. Reduces photosynthetic area.

How to identify

Folded leaves with a green caterpillar inside. Adult moths are light brown with dark wavy lines on wings, often seen flying in zig-zag patterns at dusk. Unfold affected leaves to find larvae. Threshold: 15% folded leaves before flowering.

Damage

Adults and nymphs pierce developing grains and suck out the milky contents, leaving empty or partially filled grains with distinctive feeding punctures. The grain turns brown at the puncture point. Heavy damage makes the rice unmarketable due to grain discoloration.

How to identify

Slender green or brown bugs (15-17mm) with a characteristic foul smell when disturbed. Most active early morning and late evening. Found on panicles during grain fill. Listen for their distinctive "clicking" sound in the field at dawn. Threshold: 5 bugs per hill.

Damage

Feeds on young seedlings and transplants, cutting stems at the base and destroying entire hills. Can destroy 10-40% of a newly transplanted field within days. Most damaging in the first 10-14 days after transplanting when seedlings are tender.

How to identify

Large snails (up to 8cm) with bright pink egg masses laid above the waterline on stems, field bunds, and irrigation channels. Snails are most active at night. Look for cut seedling stumps at the water surface and pink egg clusters on any vertical surface.