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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 #402999
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: Galls formed by Aceria genistae (Acari: Eriophyidae) alter resource allocation of the invasive weed Scotch broom (Cytisus scoparius)

Author
item Sarratt, Jacqueline
item PERRYMAN, MATTHEW - Solano County Department Of Agriculture
item Pratt, Paul

Submitted to: Biocontrol Science and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/7/2023
Publication Date: 8/10/2023
Citation: Sarratt, J.V., Perryman, M., Pratt, P.D. 2023. Galls formed by Aceria genistae (Acari: Eriophyidae) alter resource allocation of the invasive weed Scotch broom (Cytisus scoparius). Biocontrol Science and Technology. 10.1080/09583157.2023.2245984.
DOI: https://doi.org/10.1080/09583157.2023.2245984

Interpretive Summary: Ideally, weed biological control agents only attack the target pest and suppress the weed to a point that it is no longer considered invasive. A new gall-forming mite recently arrived in the western US and attacks Scotch broom, an invasive shrub in California, USA. Although feeding by these mites clearly induces galls on the weed, the effect of the mite on overall plant vigor and reproduction is unclear. We compared the weight of several Scotch broom plant parts (like leaves, stems, seed pods, etc.) between two groups:heavily or lightly galled plants at three northern California sites. Most structural components, including plant height, stem biomass, and leaf biomass, were similar regardless of galling intensity. However, both the number of seeds per plant as well as canopy volume were reduced in heavily versus lightly galled plants. This suggests that the gall mites reduce seed production, which is helpful in the management of this weed. The gall mite is a relatively new arrival in California but is already causing measurable impacts to plant performance, which are expected to increase locally and regionally over time.

Technical Abstract: An ideal biological control agent is both host-specific and reduces the invasive potential of the target. The Scotch broom gall mite, Aceria genistae, is a highly specialized herbivore of Cytisus scoparius (Scotch broom), an invasive shrub in California, USA. Although feeding by these mites clearly induces localized tissue distortion, the effect of A. genistae on overall host vigour and reproduction has not been assessed. Here we compare biomass allocation across various tissue types between two groups, heavily or lightly galled plants, at three northern California sites. Most structural components, including plant height, stem biomass, and leaf biomass, were similar regardless of galling intensity. However, both the number of seeds per plant as well as canopy volume were reduced in heavily versus lightly galled plants. This suggests A. genistae galls induce a reallocation of resources from seed production to the maintenance of foliage and stems. Aceria genistae is a relatively new arrival in California but is already causing measurable impacts to plant performance, which are expected to increase locally and regionally over time.