Rice leaf folder (Cnaphalocrocis medinalis)

Cnaphalocrocis medinalis (Guenee), the rice leaf folder, is a widespread migratory crambid moth pest of paddy across Asia. Larvae stitch leaf edges together with silk and feed inside the fold, leaving longitudinal whitish translucent streaks of scraped epidermis.

Identification and symptoms

Diagnostic damage is the folded leaf with parallel white streaks visible when the fold is opened. Larvae are pale green, slender and active. Adults are small, ochreous-brown moths with a wavy dark transverse band on each forewing. The pest peaks at maximum tillering through booting.

Host crops and life cycle

The pest is monophagous on rice and breeds continuously through the cropping season. Adults migrate over short to medium distances; eggs are laid along the leaf midrib. Populations build under high nitrogen, high humidity and shaded canopies, and frequently co-occur with yellow stem borer (Yellow Stem Borer Paddy) - prompting joint management strategies.

Damage and economic impact

By reducing functional leaf area at boot and panicle stages, heavy folder infestations lower grain filling and final yield. Routine pest surveys across Asian rice systems track leaf folder alongside stem borer and brown planthopper as the core foliage-feeding pest complex.

Management

Cultural: maintain open canopies; split nitrogen rather than over-applying basal N; protect Trichogramma and braconid parasitoids by minimising broad-spectrum sprays.
Chemical: ICAR-supported trials confirm chlorantraniliprole 0.4% GR broadcast at tillering (Paddy Tillering Spray 25 50 Dat) is effective; lambda-cyhalothrin, fipronil, acetamiprid and cartap are alternative actives. Co-management with stem borer chemistries is standard because the life stages overlap.

References

Rice leaffolder. IRRI Rice Knowledge Bank.
Bio-efficacy of chlorantraniliprole 0.4% GR against rice leaf folder and yellow stem borer. ICAR Indian Journal of Agricultural Sciences.