Caseworm damage in rice
RICE CASEWORM (Nymphula depunctalis) causes severe damage in current season in many rice-growing areas.
Nature of damage
The light greenish larva cuts the leaf blade into small bits and constructs tubular cases. The larva remains inside a constructed tubular case and feeds by scraping the under surface of the leaf blade leaving the upper epidermis intact. Affected plants show characteristic white patches on the leaf blades. As a result, the plants become stunted and lose vigour. Finally the severely affected plants get killed. Affected rice fields will have large number of leaf cases floating on the standing water.
Pest biology
The adult moth is small with pale brown markings on the wings. Eggs are laid singly on the leaves and the incubation period is 3-5 days.
The larva is light green in colour after constructing the leaf case starts feeding on the leaf tissues.
It is semi aquatic in habitat and with the help of filamentous gills on the larval body it derives oxygen from the little water inside the leaf case. Larval period lasts for 15-20 days. Grown up larvae pupate at the base of tillers and whitish adult moths emerge in 5-7 days.
Management practices
- The larval cases may be made to fall down in the standing water in the field by passing a long rope across the field and then they may be collected by draining the field.
- Draining and drying of the field at least for 1-2 days.
- Setting up of light traps to capture the adult moths.
- Mixing 1-2 litres of kerosene with rice bran (or) farmyard manure and sprinkling them on the standing water in an acre field. (or)
- Spraying quinalphos (or) endosulfan at 400-500 ml/acre in the early morning or late evening hours.
T. ABDUL RAZAK
M. ANANTHAN& G. SRINIVASAN
Coastal Saline Research Centre, Tamil Nadu Agricultural University
Ramanathapuram
Tamil Nadu
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