Field Identification
Small gray weevils that dive rice paddies to lay eggs in leaf sheaths; larvae mine roots and cut nutrient uptake so plants yellow in arcs—classic rice water weevil signature across flooded production.
Adults swim and fly between fields; semiaquatic larvae with hooks attach to roots underwater. Damage shows as stunted tillers and reduced yields, worst where permanent flood comes early.
How to Deal With It
Organic Control Methods
Limited organic options in flooded rice; neem-based materials may be used on labels for nursery or aerobic systems—check certifier before treating aquatic production.
Beauveria bassiana can infect overwintering adults and larvae in some studies; mermithid nematodes have been evaluated against larvae. Wolf spiders (e.g., Pardosa spp.) and other generalist predators take adults and larvae at field margins.
Delay permanent flood to let plants outgrow vulnerable stages; drill-seeded delayed flood reduces injury; destroy volunteer rice and weed grasses that bridge populations.
Maintain levees to prevent stray water that spreads adults; flush fields briefly in some systems to move larvae—extension-specific.
Monitor with floating traps or sweep nets along levees at establishment; rotate to soybeans or other non-hosts.
Let Nature Handle It
Natural Enemies
- Wolf Spiders (Lycosidae)
- Ground Beetles (Carabidae)
- Spiders
- Entomopathogenic Fungi
Threat Map