Sternechus

Schoenherr, C.J., 1826

true weevils

Sternechus is a of true ( ) containing more than 50 described . The genus is best known for Sternechus subsignatus, a significant agricultural pest of soybean in South America known locally as 'picudo grande' (big weevil). This species was first detected in southern Brazil in the 1970s and has since spread to northern Brazil and Argentina, where it causes through stem boring that can result in stand loss. Some species in the genus have been treated as distinct species in certain regions; for example, S. subsignatus in northern Argentina is sometimes considered S. pinguis. The genus is part of the extraordinarily diverse Curculionidae, which with approximately 60,000 species represents one of the largest families in the animal .

Sternechus paludatus by (c) Sue Carnahan, some rights reserved (CC BY), uploaded by Sue Carnahan. Used under a CC-BY license.

Pronunciation

How to pronounce Sternechus: /ˈstɛrnɛkʊs/

These audio files are automatically generated. While they are not always 100% accurate, they are a good starting point.

Images

Habitat

Agricultural systems, specifically soybean commercial fields under no-till systems. conceal themselves in soil or under during daylight hours to avoid sunlight.

Distribution

South America, with confirmed records from Brazil (southern and northern regions), Argentina (Salta and Tucumán Provinces), and Uruguay. The has a Neotropical distribution.

Seasonality

exhibit peak activity at dawn (6–8 a.m.) and dusk (6–8 p.m.). Mating occurs primarily at night (12 a.m.–2 a.m.), and peaks at dawn (4–6 a.m.). Adults are active during most of the day except for reduced activity between 10 a.m. and 2 p.m.

Host Associations

Glycine max - pestsoybean

Life Cycle

are laid in ring-shaped cuts prepared by females in the epidermal tissue of stems, predominantly in main stems (87%) and plant sections. hatch and bore into stems at the site, remaining inside throughout their development without vertical movement. Larvae feed on stem medulla tissue, causing localized swelling with dried tissue. emerge and exhibit diel vertical patterns.

Behavior

display pronounced diel vertical : moving to the upper third of plants at night, then descending to the lower third of plants and soil during daylight hours. They exhibit negative , concealing themselves under or burying in soil to avoid sunlight. Both sexes produce and respond to , with release peaking during photophase (4–6 hours after light onset).

Ecological Role

Agricultural pest causing damage during early vegetative stages of soybean; formation on stems affects growth and can lead to stand loss. Considered the main pest of soybean in southern Brazil.

Human Relevance

Significant economic pest of soybean production in South America. Management strategies include with grass , for control during early vegetative stages, and foliar . Research is ongoing to identify and synthesize components for potential and control applications.

Similar Taxa

Promecops carinicollisAlso a pest of soybean in the same region (Tucumán Province, Argentina), but distinguished by smaller size (3–4 mm vs. larger S. subsignatus), mottled appearance with elytral blotches, and feeding limited to leaf margins causing scalloped edges rather than stem boring.
Rhyssomatus subtilisAnother pest of soybean in Tucumán Province, Argentina, but distinguished by larval feeding within developing pods rather than stem boring, and feeding that clips leaf .

More Details

Pheromone biology

S. subsignatus produces an with at least five male-specific compounds. release is dependent on presence of food, and release peaks during photophase coincide with peak field activity.

Taxonomic note

S. subsignatus in northern Argentina (Salta and Tucumán Provinces) is sometimes treated as a distinct , S. pinguis, though this distinction requires further clarification.