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Rice leaf folder (aaku mudata)

The rice leaf folder, Cnaphalocrocis medinalis (Crambidae), known in Telugu as aaku mudata, is a migratory Asian defoliator and one of the principal foliage-feeding pests of paddy. Larvae stitch leaf margins together with silk and feed inside the resulting fold.

Identification and symptoms

Affected leaves carry longitudinal whitish translucent streaks where the larva has scraped the epidermis, and the leaves are visibly folded along the long axis. Heavy infestations reduce the photosynthetic area at the upper canopy, with the flag leaf and adjacent leaves most affected during the boot and panicle stages.

Host crops and life cycle

The pest is essentially monophagous on rice. Adults are weakly migratory greyish-brown moths with a dark transverse band on the wings. Eggs are laid singly or in pairs along the midrib of young leaves. Outbreaks are favoured by high nitrogen rates, high humidity and shaded fields, conditions that also predispose crops to brown planthopper (Brown Planthopper Paddy) and yellow stem borer (Yellow Stem Borer Paddy).

Damage and economic impact

Heavy defoliation at boot to milk stages reduces grain filling and 1000-grain weight. Pest pressure varies by year and region, and IRRI long-term data sets show that yield losses from leaf folder are often modest at moderate infestations, but can be substantial when boot-stage flag leaves are stripped.

Management

  • Cultural: avoid excess nitrogen; maintain open canopies; conserve egg parasitoids (Trichogramma spp.) and larval parasitoids by limiting broad-spectrum sprays.
  • Chemical: lambda-cyhalothrin, fipronil, acetamiprid, imidacloprid, cartap and chlorantraniliprole are effective actives. ICAR trials show that broadcast chlorantraniliprole 0.4% GR at tillering (Paddy Tillering Spray 25 50 Dat) suppresses both leaf folder and yellow stem borer, with grain residues below 0.01 ppm.

See also: Leaf Folder Paddy 2, Yellow Stem Borer Paddy, Stem Borer Paddy, Brown Planthopper Paddy, Paddy Tillering Spray 25 50 Dat.

References

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