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ARS Home » Pacific West Area » Albany, California » Western Regional Research Center » Invasive Species and Pollinator Health » Research » Publications at this Location » Publication #418735
Research Project: Biological Control of Invasive Pests in Agroecosystems and Wetland, Forest and Rangeland Ecosystems in the Far Western U.S.

Location: Invasive Species and Pollinator Health

Title: Sex-ratio distortion in a weed biological control agent, Ceratapion basicorne (Coleoptera: Brentidae), associated with a species of Rickettsia

Author
item GLADEM, KRISTI - Colorado Department Of Agriculture
item RUGMAN-JONES, PAUL - University Of California, Riverside
item SHELTON, EMMA - Colorado Mesa University
item HANRAHAN, KELLY - Colorado Department Of Agriculture
item BEAN, DAN - Colorado Department Of Agriculture
item Rector, Brian

Submitted to: Environmental Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/29/2024
Publication Date: 1/1/2025
Citation: Gladem, K.B., Rugman-Jones, P.F., Shelton, E.K., Hanrahan, K.S., Bean, D.W., Rector, B.G. 2025. Sex-ratio distortion in a weed biological control agent, Ceratapion basicorne (Coleoptera: Brentidae), associated with a species of Rickettsia. Environmental Entomology. 54(1):109-118. https://doi.org/10.1093/ee/nvae115.
DOI: https://doi.org/10.1093/ee/nvae115

Interpretive Summary: The primary American rearing colony of an imported weevil that was recently approved as a biocontrol agent of the noxious weed yellow starthistle (YST) became infected with a bacterium that causes infected females to only produce female offspring, threatening to crash the colony, as well as field populations of weevils that have been released to control YST. Genetic studies were undertaken to identify the causal agent of the male-preventing disease and antibiotic treatments were tested to attempt to cure the weevil colony of the infection. A species of Rickettsia was determined to be associated with male-prevention and treatment of weevils with tetracycline was shown to effectively remove the rickettsia and restore a normal ratio of half-male, half-female in the project of treated mothers. Millions of dollars are lost annually to management of YST and reduced utility of YST-infested lands. The work presented here will ensure that the weevil biocontrol agent will remain available for control of YST.

Technical Abstract: Many endosymbionts of insects have been shown to manipulate and alter their hosts’ reproduction with implications for agriculture, disease transmission, and ecological systems. Less studied are the microbiota of classical biological control agents and the implications of unintended endosymbionts in laboratory colonies for field establishment and target pests or non-target organisms. While native-range field populations of agents may have a low incidence of vertically transmitted endosymbionts, quarantine and laboratory rearing of inbred populations may increase this low prevalence to fixation in relatively few generations. Fixation of detrimental endosymbionts in founding biological control agent populations prior to release may have far-reaching effects. Significant female-biased sex-ratio distortion was found within laboratory populations of the weevil Ceratapion basicorne, a classical biological control agent that was recently approved for use against yellow starthistle, Centaurea solstitialis. This sex ratio distortion was observed to be maternally inherited and reversible through antibiotic treatment of the host insect. Molecular diagnostics identified a Rickettsia sp., as the only bacterial endosymbiont present in breeding lines with distorted sex-ratios and implicated this as the first reported Rickettsia associated with sex-ratio distortion within the superfamily Curculionoidea.