Biology, chemical ecology, and sexual dimorphism of the weevil Myllocerus undecimpustulatus undatus (Coleoptera: Curculionidae)

Authors: JUSTIN, GEORGE - UNIVERSITY OF FLORIDA; SHAREEF, SANA - HARVARD UNIVERSITY; LAPOINTE, STEPHEN

Submitted to: Florida Entomologist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/25/2019
Publication Date: 9/26/2019
Citation: Justin, G., Shareef, S., Lapointe, S.L. 2019. Biology, chemical ecology, and sexual dimorphism of the weevil Myllocerus undecimpustulatus undatus (Coleoptera: Curculionidae). Florida Entomologist. 102(3):464-468. https://doi.org/10.1653/024.102.0305.
DOI: https://doi.org/10.1653/024.102.0305

Interpretive Summary: The Sri Lankan weevil (SLW) is becoming a major pest of ornamentals and tropical fruit trees in the southern United States including Florida. Recent findings of this species in Florida citrus groves justify research into its biology and ecology. Identification of odors used by the weevil to find its food plants will help to develop insect control strategies. Female weevils collected in southeastern Florida were larger than males in length of head, abdomen and overall. Females, but not males, have a characteristic marking underneath extending from the thorax to the abdomen. Scanning electron microscopic images revealed that females had fewer egg-shaped scales in this region of characteristic black-gray marking, and more plumose (feathery) scales compared with males. SLW preferred peach plants over weeds or grasses in peach orchards. We identified peach odors that stimulate antennal responses from both males and females. Behavioral assays are underway to identify those odors that could be used to attract or disrupt these weevils.

Technical Abstract: Myllocerus undecimpustulatus undatus Marshall (Coleoptera: Curculionidae), also known as the Sri Lankan weevil (SLW), is becoming a major pest of ornamentals and tropical fruit trees in the southern United States including Florida. Recent findings of this species in Florida citrus groves justify research into its biology and ecology. Identification of semiochemicals involved in their behavioral and chemical communication will help to develop insect control strategies. We studied morphological and sexually dimorphic characters of this species as an aid to rapid separation of sexes for studies aiming to identify semiochemicals that may be of value in management. Female weevils collected from the field in southeastern Florida were significantly larger than males in length of head, abdomen and overall length. Females, but not males, have a characteristic black-gray marking extending from the ventral mesosternum to the second abdominal segment. Scanning electron microscopic images revealed that females had fewer ovate-to-obovate scales in this region of characteristic black-gray marking, and more plumose scales compared with males. Host choice and oviposition studies showed that SLW prefer peach plants over weeds or grasses in peach orchards. Electroantennogram recordings using different peach volatiles identified peach odorants that can elicit significantly higher antennal responses. Both male and female SLW antennae were highly responsive to these volatiles. Behavioral assays in olfactometers are underway to identify those semiochemicals that could be used as attractants or disruptants.