| [Image: RWW adult on rice leaf] |
| [Image: rice water weevil feeding scars] |
| [Image: rww puparia on roots] |
Overview:
Rice water weevil (RWW) adults are grayish-brown weevils (1/8 inch long). Adults leave overwintering sites, invade rice fields and begin feeding on the leaves of rice plants. Females deposit eggs in the leaf sheath at or below the waterline. White larvae emerge from eggs in about one week and develop through four instars while feeding on the roots of rice plants. Larvae pupate in cocoons that are covered with a compact layer of mud and are attached to rice roots. The life cycle from egg to adult takes about one month.
Facts:
- Application of the permanent flood triggers females to lay eggs in rice leaf sheaths.
- Economic damage caused by larval root pruning reduces the number of tillers produced by the damaged plant.
What should you look for:
- Elongate feeding scars caused by adult feeding.
- Infested stands may be thin in appearance and contain yellow plants.
How you can manage rice water weevils:
- Avoid late planting of rice.
- Delay the application of permanent flood.
- Apply a pesticide to control rice water weevils at the correct time. Adults must be controlled before egg-laying occurs. Sample larvae by taking core samples.