Gray Sunflower Seed Weevil: Appearance, Territory, Damage and Life Cycle

Latin Name: Smicronyx Sordidus

Appearance: The gray sunflower seed weevil Smicronyx sordidus belongs to the Curculionidae family of weevils. The pale gray seed weevil is around 8 mm (1/4 inch) length, with a gently curving nose nearly half as long as the body. Adults can often be discovered hidden between the bracts of sunflower buds before or during bloom. Larvae feed on growing seeds, causing a galling reaction that leaves the damaged seeds bloated but empty.

Hosts Plants: Sunflower

Territory: America and Europe

Damage Insect Cause: The gray seed weevil has no economic barrier, and it is typically regarded a less problematic pest than its relative, the red seed weevil. Female fecundity is decreased, which means that each female lays fewer eggs and destroys fewer seeds. Another explanation is that gray seed weevil infestation has a lower risk of postharvest degradation since galled seeds are normally eliminated during most conventional seed threshing and cleaning operations, whereas this is not true for red seed weevil-infested seeds. As a result, gray seed weevil-caused production losses are difficult to measure and sometimes go unrecognized.

Life History and Habits: The species’ life cycle lasts barely a year. Sunflower buds are eaten by both sexes, and frequently before they open. Adults emerge in late spring and generally invade sunflower fields as the plants near reproductive stages. Adults of both sexes are frequently seen on sunflower buds before they open, feasting on plant tissues behind the bracts while inflicting no harm. Females prefer late-bud flowers for oviposition, placing their eggs singly at the base of growing seeds. When larvae hatch, they burrow into the seeds at their base, killing the ovaries. When the larvae reach adulthood, they depart the seeds and fall to the ground, where they look for overwintering locations in the soil. Pupation happens in June of the next year.