Does spruce aphid defoliation alter Engelmann spruce resistance to spruce beetle?

Abstract

The spruce beetle has been observed attacking spruce aphid-defoliated trees, although whether spruce beetle attacks are facilitated by spruce aphid defoliation is uncertain. The potential for spruce aphid to incite spruce beetle outbreaks is of great concern for managers as spruce populations are already declining across the West and spruce aphid outbreaks may increase with warmer winters. No previous studies have investigated impacts of spruce aphid defoliation on spruce beetle performance or defenses of Engelmann spruce. This project addressed impacts of spruce aphid defoliation on spruce beetle performance and tree defenses with a novel experiment during an exceptional multidecadal megadrought (2000–2021).

Parent Publication

• Forest Health Monitoring: Evaluation Monitoring project summaries 2023

Citation

Kolb, Thomas; Gaylord, Monica; Grady, Amanda; Hansen, Matt; Lynch, Ann; McMillin, Joel; Runyon, Justin. 2025. Does spruce aphid defoliation alter Engelmann spruce resistance to spruce beetle? In: Conkling, B.L.; Pandit, K., eds. Forest Health Monitoring: Evaluation Monitoring project summaries 2023. Gen. Tech. Rep. WO-105a. Washington, DC: U.S. Department of Agriculture, Forest Service. 81–87: Chapter 10. https://doi.org/10.2737/WO-GTR-105a-Chap10.