Trichobaris trinotata

Adults measure approximately 4.4 mm in length and 1.7 mm in width. The body is black but appears gray due to dense minute scales covering most of the surface. Three bare, dark spots at the base of the elytra—one anterior and two lateral—are diagnostic and give the species its name. The rostrum bends sharply downward at its base. The head lacks scales. These features distinguish it from other small, dark weevils in the genus and family.

Associated with plants in the family Solanaceae. Native populations occur on Carolina horsenettle (Solanum carolinense). Agricultural populations found on cultivated potato crops. Adults overwinter in dead potato haulms or stems of other Solanaceae.

North America. Recorded from Canada (Ontario, Québec) and the United States.

Adults emerge from reproductive diapause in spring. Egg laying begins in May. Larval development spans up to 106 days. Adults emerge from pupation approximately 12 days later. Single generation per year.

Herbivorous, feeding on Solanaceae. Larvae develop inside stems of host plants. Adults feed on leaves, producing ragged holes. Documented hosts include potato (Solanum tuberosum), eggplant (Solanum melongena), Carolina horsenettle (Solanum carolinense), buffalo bur (Solanum rostratum), European black nightshade (Solanum nigrum), and groundcherry species (Physalis).

• Solanum tuberosum - primary agricultural hostlarvae cause significant damage through stem tunneling
• Solanum carolinense - native hostweed reservoir; plant shows high tolerance with negligible impact from herbivory
• Solanum melongena - occasional host
• Solanum rostratum - occasional host
• Solanum nigrum - occasional host
• Physalis spp. - occasional hostseveral species of groundcherry

Eggs are deposited singly in holes chewed by the rostrum into stems, leaf stalks, or leaf axils. Eggs hatch in approximately one week. Larvae are white, legless, and create tunnels up to 30 cm long through stem tissues over five to six instars. Pupation occurs within the stem. Adults emerge after about 12 days. One generation per year. Adults overwinter in dead host plant material.

Females preferentially oviposit on larger, healthier plants, likely because these provide better larval resources. Larval feeding is endophytic, occurring entirely within host stems.

Carolina horsenettle serves as a reservoir host, maintaining populations that can switch to cultivated potato. The native host's high tolerance to herbivory enables persistent weevil populations without controlling the weed. Parasitoids include the braconid wasp Nealiolus curculionis and less frequently the eurytomid wasp Eurytoma tylodermatis.

Economic pest of potato crops. Larval stem tunneling causes primary damage; adult leaf feeding is secondary. Formerly considered a serious pest, but modern management practices—particularly burning or removal of crop residues to destroy overwintering adults—have reduced its impact.

• Other Trichobaris speciescongeneric weevils lack the three distinctive dark elytral spots and specific rostral curvature of T. trinotata
• Other small black CurculionidaeT. trinotata distinguished by combination of small size (~4.4 mm), gray-scaled appearance with three bare dark spots on elytra, and sharply downcurved rostrum

• BugGuide
• Wikipedia
• GBIF taxonomy match
• iNaturalist taxon
• NCBI Taxonomy
• Catalogue of Life
• The notoriously destructive potato stalk borer (Trichobaris trinotata) has negligible impact on its native host, Solanum carolinense (horsenettle)