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Rice Case Worm

Rice Case Worm

Parapoynx stagnalis


In a Nutshell

    damage is characterized by leaves cut at right angles as with a pair of scissorsLeaf cases enclosing the larvae are floating on waterLarvae feed by scraping the leaf tissue, leaving ladder-like structures of hard fibers

Hosts: %1$s

· Rice


The young P. stagnalis larva causes linear grazing of leaves. Rice case worms cut off rice leaves tips at right angles to make leaf cases. Caseworm damage is characterized by leaves cut at right angles as with a pair of scissors and leaf cases floating on water. Larvae feed by scraping the leaf tissue, leaving the papery upper layer of the leaf. Leaves that were fed upon are also left with a ladder-like structures of hard fibers. Damage symptoms can be confused with other defoliating insect pests. To confirm caseworm, visually inspect 1-the ladder-like leaf tissues, 2-cut leaves, and 3-the presence of leaf cases attached onto leaf sheaths and floating in the water.


The insect is most likely to be found in rice fields with standing water, in both wetland and irrigated environments. Transplanting young seedlings also favors the development of the insect. The insect is commonly found in rice fields in low populations.

Biological Control

Encourage biological control agents such as snails (feed on eggs), hydrophilid and dytiscid water beetles (feed on larvae), spiders, dragonflies, and birds (feed on adults). Apply ash or spray neem leaf extracts to the place where insects are found.

Chemical Control

Always consider an integrated approach with preventive measures together with biological treatments if available. Use foliar treatments of carbamate insecticides and fipronil and avoid pyrethroids, to which the pest has become tolerant.

Preventive Measures

    Early planting reduce the incidenceUse wider spacing (30 × 20 cm) when plantingTransplant older seedlings and destroy possible remaining eggsDrain the field and use filters to catch worms when re-irrigating after 2-3 daysUse recommended fertilizer applications