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ARS Home » Plains Area » Fort Collins, Colorado » Center for Agricultural Resources Research » Rangeland Resources & Systems Research » Research » Publications at this Location » Publication #415022
Research Project: Developing Precision Management Strategies to Enhance Productivity, Biodiversity, and Climate Resilience in Rangeland Social-ecological Systems

Location: Rangeland Resources & Systems Research

Title: Managing European elm scale in the period of neonicotinoid insecticide resistance

Author
item SITS, RACHEL - Davey
item Peirce, Erika
item AL-AKEEL, RASHA - King Saud University
item SCHREINER, MELISSA - Colorado State University
item BURNS, WENDLIN - Colorado State University
item CRANSHAW, WHITNEY - Colorado State University

Submitted to: ARBORICULTURE AND URBAN FORESTRY
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/20/2024
Publication Date: 2/25/2025
Citation: Sits, R.A., Peirce, E.S., Al-Akeel, R., Schreiner, M., Burns, W., Cranshaw, W.S. 2025. Managing European elm scale in the period of neonicotinoid insecticide resistance. ARBORICULTURE AND URBAN FORESTRY. Volume 51(2):1-12. https://doi.org/10.48044/jauf.2025.004.
DOI: https://doi.org/10.48044/jauf.2025.004

Interpretive Summary: The European elm scale, Gossyparia spuria (Modeer) (Hemiptera: Eriococcidae) has been a marked pest on American elm (Ulmus americana) in western states since its invasion. Tactics to control this insect pest have been largely based on chemical controls; first insecticidal sprays and then systemic applications. However, the emergence of insecticide-resistant scales in recent years has posed a notable challenge. Through experiments, we were able to conclude there is European elm scale resistance to neonicinoids. Since this is the main pesticide used to manage this insect, we also explored alternative insecticides. Based on our findings, the current recommendation for control of neonicotinoid resistant European elm scale is using the insect growth regulator pyriproxyfen (Distance), which is applied as a spray. In addition to pesticides, we found several natural insect enemies that attacked the European elm scale in Colorado. We captured 11 species of wasps that parasitize the European elm scale. Additionally, through cultivar resistance experiments, we have identified several elm varieties that show promise in reducing European elm scale damage, suggesting their suitability for planting in urban landscapes.

Technical Abstract: The European elm scale, Gossyparia spuria (Modeer) (Hemiptera: Eriococcidae) has been a marked pest on American elm (Ulmus americana) in western states since its invasion. Tactics to control this insect pest have been largely based on chemical controls; first insecticidal sprays and then systemic applications, but in recent years insecticide resistant scales have become an apparent problem. This paper (1) outlines how insecticide resistance was likely established in Colorado, (2) documents neonicotinoid resistance in this plant parasite by showing scale insects feeding on trees with high levels of imidacloprid insecticides, and (3) explores alternative control options that will be integral to maintaining American elms as part of the urban landscape in western states. Trials were set up to explore alternative insecticides that could be used to manage European elm scale, controls include non-neonicotinoid insecticides where resistance is established, surveys for predator and parasitoid biological control agents, and resistant hosts.