Cylindrocopturus adspersus

LeConte, 1876

sunflower stem weevil

Cylindrocopturus adspersus, commonly known as the sunflower stem , is a true weevil in the . are small, grayish- with irregular whitish markings, approximately 5 mm in length. The has a single per year, with developing inside sunflower stems and in chambers hollowed out at the base of the . It is recognized as an occasional but potentially serious pest of cultivated sunflowers in North America, capable of reducing yields by up to 50% in heavily infested fields.

Cylindrocopturus adspersus by (c) Catherine C. Galley, some rights reserved (CC BY), uploaded by Catherine C. Galley. Used under a CC-BY license.

Conoderinae (10.3897-zookeys.683.12080) Figures 19–36 by Anzaldo SS (2017) Review of the genera of Conoderinae (Coleoptera, Curculionidae) from North America, Central America, and the Caribbean. ZooKeys 683: 51-138. https://doi.org/10.3897/zookeys.683.12080. Used under a CC BY 4.0 license.

Pronunciation

How to pronounce Cylindrocopturus adspersus: /sɪˌlɪndroʊˈkɒptərəs ædˈspɜːrsəs/

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Identification

are distinguished from similar stem by their small size (approximately 5 mm), grayish- coloration with irregular whitish markings, and mottled appearance. The black sunflower stem weevil (Apion occidentale) is smaller (approximately 3 mm), entirely black, and belongs to the Brentidae. The sunflower -clipping weevil (Haplorhynchites aeneus) is larger (approximately 8 mm), metallic black, and belongs to the family . of C. adspersus are creamy with brown heads and found tunneling in sunflower stem pith, whereas larvae of the cocklebur weevil (Rhodabaenus quinquepunctatus) are larger and leave more conspicuous tunnels.

Images

Habitat

Agricultural fields and natural areas supporting sunflower plants; specifically associated with cultivated sunflower (Helianthus annuus) and wild sunflower . are found on sunflower stems and foliage. develop within the pith of sunflower stems. chambers are located in the woody tissue of old sunflower stalks.

Distribution

North America: recorded in the United States from Colorado, Texas, North Dakota, South Dakota, and Minnesota; present in the Canadian Prairie Provinces including Saskatchewan (first recorded 1984 near Carnduff, with subsequent establishment in the Carnduff, Estevan, and Weyburn areas). Distribution corresponds to major sunflower-growing regions of the northern Great Plains.

Seasonality

emerge from chambers in May or June. occurs over a 2- to 5-week period following adult . develop through summer, descending to stem bases in late summer or fall. Single per year; adults and larvae enter through winter, resuming activity in spring.

Diet

feed on sunflower leaves and stems without causing significant . feed internally on sunflower stem pith, destroying vascular tissue and weakening structure.

Host Associations

Helianthus annuus - primary cultivated and wild sunflower; tunnel in stems, feed on foliage
Helianthus spp. - wild sunflower

Life Cycle

: deposited singly in holes chewed at the base of sunflower stems by females, protected with . : hatches and feeds internally within the stem, burrowing downward through the pith; multiple larvae may occupy a single stem (up to 100 reported). Mature larva: descends to base of and hollows out an chamber in woody tissue. : develops within the overwintering chamber in spring. : emerges from chamber, feeds briefly on foliage, mates, and oviposits. Single per year with overwintering larval .

Behavior

females exhibit specific site selection , chewing holes in sunflower stem bases and depositing single protected by . exhibit negative , burrowing downward through stem pith toward the base. Mature larvae construct chambers by excavating woody tissue at the stem base. Adults are cryptic and easily overlooked due to resemblance to debris when resting on stems.

Ecological Role

Primary consumer of sunflower stem tissue; significant pest of cultivated sunflower. Larval tunneling predisposes plants to (stem breakage) under wind stress. Stem damage has been associated with increased susceptibility to charcoal rot (Macrophomina phaseolina) and Fusarium solani collar rot. Serves as for , particularly Nealiolus curculionis (), which provides . rates and parasitoid composition vary regionally in the northern Great Plains.

Human Relevance

Agricultural pest of sunflower, an important oilseed in North America. Yield losses up to 50% documented in heavily infested, non-rotated, early-planted fields. results from stem prior to harvest and predisposition to fungal . Management strategies include crop , delayed planting (after mid-June in Texas High Plains), tillage to destroy stalks, and when are exceeded (two or more per from third alternate leaf stage to early stage; or one per three plants in North Dakota). including carbofuran and acephate are effective but also toxic to , potentially disrupting .

Similar Taxa

Apion occidentaleAlso called black sunflower stem ; smaller (3 mm), entirely black, Brentidae; causes minimal damage; and found among C. adspersus larvae
Haplorhynchites aeneusSunflower -clipping ; larger (8 mm), metallic black, ; stems below flower heads causing them to fall, rather than tunneling in stems
Rhodabaenus quinquepunctatusCocklebur ; larger (6–10 mm), red with black spots; larger and leave conspicuous tunnels in stem pith; associated with cocklebur and sunflower

More Details

Parasitoid relationships

The Nealiolus curculionis is the ; females lay in first- . The wasp larva enters within the weevil larva, resuming development in spring and killing the approximately 20 days after activity resumes. Both host and have single with synchronized .

Management considerations

Double- or late-planted sunflowers rarely develop severe . Non-rotated, early-planted fields in continuous sunflower production are at highest risk. Cultural control through stalk destruction and crop is emphasized in programs.