The adults of red sunflower seed weevil are 12.5 to 3 mm long and are reddish-brown. The adults of gray sunflower seed weevil are slightly larger and gray in color. The larvae of both species are small, cream-colored, legless and C-shaped in appearance.The red seed weevil is the more common of the two weevils.
Newly emerged adults feed on the bracts of sunflower buds. When the sunflower head begins to bloom, the adults feed on the pollen, and as the seeds begin to fill, lay eggs within the seed.
The small, white, oval-shaped eggs hatch in approximately one week. Larvae consume the meat of the seed, causing the economic loss. Most seeds are only partially consumed or destroyed by the larvae and the damaged seeds have lower oil content than the undamaged seeds. The economic loss caused by the larval feeding includes the loss of both seed weight and oil content.
Larvae normally drop from the head to the soil after completing their development, but a small percentage may remain in the seed and be present in the harvested seed. If larvae drop from the seed, an exit hole is present on the side of the seed. The insect cannot survive in storage, and is not a stored product pest.