Sitona cylindricollis

Fåhraeus, 1840

sweetclover weevil

Sitona cylindricollis, the sweetclover weevil, is a broad-nosed weevil in the Curculionidae. It is a documented agricultural pest of sweet clover (Melilotus officinalis) and alfalfa/lucerne (Medicago sativa). feed on above-ground foliage, causing defoliation damage that is most severe during late summer . Larvae feed on root nodules and root tissue underground. The exhibits temperature- and light-dependent , with peak flight activity occurring in morning hours when ambient temperatures reach threshold levels.

Sitona cylindricollis by (c) Renee MacQuarrie, some rights reserved (CC BY), uploaded by Renee MacQuarrie. Used under a CC-BY license.

Sitona-cylindricollis-01-fws by Francisco Welter-Schultes. Used under a CC0 license.

Sitona-cylindricollis-11-fws by Francisco Welter-Schultes. Used under a CC0 license.

Pronunciation

How to pronounce Sitona cylindricollis: /sɪˈtoʊnə sɪˌlɪndrɪˈkoʊlɪs/

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

Identification

As a member of the broad-nosed weevil Entiminae, distinguished from other weevil groups by the short, broad rostrum. Differentiation from other Sitona requires examination of minute morphological characters not detailed in available sources. are associated with sweet clover and alfalfa fields, which may aid in field recognition.

Images

Habitat

Agricultural fields, specifically those cultivated for sweet clover (Melilotus officinalis) and alfalfa/lucerne (Medicago sativa). Associated with open, sunlit environments where plants grow.

Distribution

North America, with documented occurrence in the Canadian prairies and mid-western United States. Also recorded from Europe (Austria, Bulgaria, Czechoslovakia, Denmark, Finland, France, Germany, Hungary, Italy, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland, Yugoslavia) and Asia (Afghanistan, China, Iran, Israel, Tibet, former U.S.S.R.) per distribution map records.

Seasonality

are active during growing season of plants. occur primarily during a short period in May, with peak flight activity between 09:00-11:00 hours. Defoliation damage is most severe when feeding occurs during the from 15 August to 20 September.

Diet

feed on foliage of sweet clover (Melilotus officinalis) and alfalfa/lucerne (Medicago sativa). Larvae feed on root nodules and root cortex tissue of these plants.

Host Associations

Melilotus officinalis - primary plantsweet clover; feed on foliage, larvae feed on root nodules and roots
Medicago sativa - primary plantalfalfa/lucerne; feed on foliage, larvae feed on root nodules and roots

Life Cycle

Complete with , larval, pupal, and stages. Larvae develop underground, feeding on root nodules and root tissue of plants. occurs near the soil surface. Specific timing of developmental stages not documented in available sources.

Behavior

exhibit pre- warming posture before takeoff. flights are induced by rising temperature and light intensity, with an ambient temperature threshold of approximately 25°C in bright sunshine (corresponding to body temperature of ~35°C). Flight activity decreases at wind speeds above 0.1 m/sec and ceases at 0.6 m/sec. Feeding and temperature increase the threshold for flight activity. Young adults typically do not fly. plant odor, specifically coumarin, serves as a significant olfactory stimulus for terminating flight and facilitating landing. Strong anemotactic response to host plant odor enables colony establishment.

Ecological Role

Agricultural pest of sweet clover and alfalfa. defoliation and larval root feeding reduce stand establishment, , and forage yield. In the Canadian prairies, typically remain below economic damage thresholds. Contributes to as prey for predatory including Cerceris weevil wasps.

Human Relevance

Economic pest in forage crop production. Damage potential includes seedling mortality at high weevil densities (1 weevil per seedling), reduced second-year forage yield from defoliation during critical late-summer period, and chronic stand decline from larval root feeding. Currently not considered a major deterrent to sweet clover production in western Canada due to typically sub-threshold levels.

Similar Taxa

Sitona hispidulusclover root curculio; also a pest of alfalfa and clovers with similar larval root-feeding habit, but differs in specific associations and damage patterns
Hypera posticaalfalfa weevil; another curculionid pest of alfalfa, but with different and

More Details

Flight behavior research

Laboratory and field studies demonstrate that temperature preference is plastic based on prior thermal experience: weevils emerging from hibernation have lower temperature preferences than those collected during summer months. High humidity inactivates weevils at all temperatures. Light does not alter temperature responses, but high temperature reverses negative phototactic .

Damage thresholds

Field cage experiments in the Canadian prairies established -dependent damage relationships: 1 weevil per 7 seedlings destroyed less than 5% of seedlings, while 1:1 ratio caused 100% mortality. For second-year plants, 4.5-9 weevils per plant caused significant yield reduction, and 18 weevils per plant caused near-total destruction of forage yield.