Original illustration by PestControlBasics.com. Use the labeled features above to confirm your identification.
🔍 Identification
Rice Weevil (S. oryzae): 2-3mm; reddish-brown with 4 pale spots on wing covers; can fly; infests rice, corn, wheat. Granary Weevil (S. granarius): 2-4mm; darker brown; no spots; cannot fly; infests wheat, rye, oats, barley. Both have the distinctive snout (rostrum) of all weevils — the definitive ID feature that distinguishes them from flour beetles.
🧬 Biology & Behavior
Females drill into grain kernels with their rostrum, deposit one egg, and seal the hole. Larvae develop entirely inside — egg, larval, and pupal stages all occur inside the kernel. Adults emerge by chewing through the kernel wall. You can spot early infestation by floating grain — hollowed kernels float.
⚠️ Damage & Health Risk
Hollow, ruined grain kernels; significant economic losses in stored grain; musty grain odor; flour from infested grain has reduced quality and baking properties. Adults of flying species (rice weevil) spread rapidly to new grain supplies.
🔧 DIY Treatment
Find and discard all infested grain. Freeze clean grain at 0°F for 72 hours to kill any undetected eggs or larvae. Transfer ALL grain products to sealed, airtight glass or hard plastic containers. Inspect regularly. Clean shelves thoroughly with white vinegar between uses. For large bulk storage, food-grade diatomaceous earth mixed into grain prevents establishment.
👷 When to Call a Pro
For grain elevator or commercial storage operations, phosphine fumigation and heat treatment are standard professional options.