applyparastyle "fig//caption/p[1]" parastyle "FigCapt" Copyedited by: OUP F&R "All rights reserved. For permissions, please e-mail" (CopyrightLine) "^nAll rights reserved. For permissions, please e-mail" (CopyrightLine) Journal of Economic Entomology, XX(XX), 2021, 1–6 https://doi.org/10.1093/jee/toab142 Research Forest Entomology Wild Bee Response to Application of the Douglas-fir Beetle Anti-Aggregation Pheromone, 3-Methylcyclohex-2-En-1-One Gabriel G. Foote,1,6,7, Justin B. Runyon,2 Christopher J. Fettig,3 Nathaniel E. Foote,4 and Darrell W. Ross1,5 1Department of Forest Ecosystems and Society, Oregon State University, Corvallis, OR 97331, USA, 2Rocky Mountain Research Station, USDA Forest Service, 1648 South 7th Street, Bozeman, MT 59717, USA, 3Pacific Southwest Research Station, USDA Forest Service, 1731 Research Park Drive, Davis, CA 95618, USA, 4Forest and Rangeland Stewardship, Colorado State University, Fort Collins, CO 80523, USA, 5Present address: Department of Entomology, School of Natural Resource Sciences, College of Agriculture, Food Systems and Natural Resources, North Dakota State University, Fargo, ND 58108, USA, 6Present address: Department of Entomology and Nematology, College of Agricultural and Environmental Sciences, University of California, Davis, Davis, CA 95616, USA, and 7Corresponding author, e-mail: [email protected] Subject Editor: Kamal Gandhi Received 12 February 2021; Editorial decision 15 June 2021 Abstract Douglas-fir beetle,Dendroctonus pseudotsugae Hopkins (DFB), is the most damaging insect pest of Douglas- fir, Pseudotsuga menziesii (Mirb.) Franco, in western North America. Individual high-value trees and stands can be protected during DFB outbreaks using the beetle's anti-aggregation pheromone, 3-methylcyclohex-2- en-1-one (MCH), which is available in several commercial formulations. However, other methylcyclohexanones similar in molecular structure to MCH have been shown to repel bees from agricultural areas. In forest systems, wild bees (Hymenoptera: Apiformes) provide essential pollination services to many forb and shrub species. Therefore, it is important to determine whether resident wild bee communities are affected in forests treated with MCH. To address this, the bee community was sampled within experimental sites located in Idaho and Montana, USA in 2016. At both sites, there was no significant difference in overall bee abundance, species rich- ness, or diversity between MCH-treated plots and untreated control plots. Overall, these results indicate that treatment of Douglas-fir with MCH does not negatively impact the resident wild bee community. Key words: bee conservation, Dendroctonus pseudotsugae, forest health, forest pollinators, 3-methylcyclohex-2-en-1-one Many flowering plants are dependent on pollination by wild bees use (Potts et al. 2010, Cameron et al. 2011, Burkle et al. 2013, Koh (Hymenoptera: Apiformes) for reproduction and persistence in tem- et al. 2016, Woodcock et al. 2017). The nontarget detrimental effects perate forests (Fontaine et al. 2005, Kremen et al. 2007, Winfree of agricultural pesticides on pollinators, especially honeybees, have et al. 2007, 2009; Hanula et al. 2015, 2016). These plants protect been recognized for decades (Anderson and Atkins 1968, Solomon water quality, prevent soil erosion, and provide food for humans and Hooker 1989) and have become increasingly apparent in recent and wildlife (Wratten et al. 2012). Additionally, forest-dwelling bee years (Kessler et al. 2015, Woodcock et al. 2017, Kopit and Pitts- species can contribute to pollination services in nearby agricultural Singer 2018). lands (Garibaldi et al. 2013, Morandin and Kremen 2013), and on a Previous studies using field and laboratory tests have identified per flower basis, wild native bees can be more effective crop pollin- chemical repellents capable of deterring honeybees from entering ators than managed honeybees (Garibaldi et al. 2013). Despite the pesticide-treated agricultural fields (e.g.,Atkins et al. 1975, Solomon ecologic and economic importance of wild bees, their populations and Hooker 1989, Mishra and Sihag 2009). Among these repellents are are facing declines from a variety of factors, including increasing cyclic ketones similar in molecular structure to 3-methylcyclohex-2- rates of habitat fragmentation, intensified agriculture, and pesticide en-1-one (MCH), the anti-aggregation pheromone of the Douglas-fir © The Author(s) 2021. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. 1 For permissions, please e-mail: [email protected]. Copyedited by: OUP 2 Journal of Economic Entomology, 2021, Vol. XX, No. XX beetle (DFB), Dendroctonus pseudotsugae Hopkins (Coleoptera: with three treatments and six replications (n = 18). Treatments in- Curculionidae) (Kinzer et al. 1971, SERA 1999), which is the most cluded: 1) MCH bubble capsules (Synergy Shield MCH, Product damaging insect pest of Douglas-fir, Pseudotsuga menziesii (Mirb.) #3311, Synergy Semiochemicals Corp., Burnaby, BC) applied at 30 Franco (Pinales: Pinaceae), in western North America (Furniss and per plot spaced on approximately a 12 × 12 m grid; 2) SPLAT MCH Carolin 1977, Furniss 2014a,b). Population densities of DFB are (ISCA Technologies Inc., Riverside, CA, USA) applied at 15 g per plot limited by the availability of optimal host material (recently dead (15 dollops spaced on a 13 × 21 m grid); and 3) untreated controls. or stressed Douglas-firs), but often increase following disturbances On each plot, one blue vane trap (SpringStar Inc., Woodinville, such as wildfires, windstorms, or defoliator outbreaks (Furniss and WA) was placed at plot center along with two yellow pan traps de- Carolin 1977). Under these conditions, DFB populations may reach ployed at 10.5 m intervals in each cardinal direction radiating from high enough densities to successfully colonize and kill large numbers plot center, for a total of eight yellow pan traps per plot. Yellow of healthy trees across a landscape for several years. The DFB anti- pan traps were 3.25 oz plastic bowls painted yellow (New Horizons aggregation pheromone, 3-methylcyclohex-2-en-1-one (MCH), sig- Supported Services, Upper Marlboro, MD) and filled to 75% cap- nals to late-arriving beetles that a tree is fully occupied, causing them acity with approx. 60 ml of water mixed with <1 ml of liquid de- to search for uncolonized or less densely populated hosts (McMullen tergent soap to reduce surface tension. Previous studies have shown and Atkins 1961, Pitman and Vité 1974, Hedden and Gara 1976). these traps to be effective in sampling bee populations in variable Commercial formulations of MCH are available for reducing un- forest habitats for direct comparison (Campbell and Hanula 2007, desirable levels of DFB-caused tree mortality. MCH bubble capsules Westphal et al. 2008, Hanula et al. 2015). Blue vane traps were were registered with the United States Environmental Protection present 10 June–27 July 2016, and catches were retrieved biweekly. Agency (USEPA) in 1999 and have been used operationally since Pan traps were deployed during four separate periods throughout 2000 (Ross et al. 2015, Ross 2021). A biodegradable formulation, the summer: 20–24 June, 27 June–1 July, 11–15 July, and 25–29 July SPLAT MCH, was developed and recently evaluated in field tests 2016. Pan traps were operated for 24 h intervals during the June (Foote et al. 2020a). Unlike the plastic used for MCH bubble cap- sampling periods, and for 48 h intervals during the July sampling sules, the inert ingredients of SPLAT MCH biodegrade in one–two periods. Every plot was sampled during each interval, but due to years. Therefore, SPLAT MCH may be a preferable treatment in lo- logistical constraints, all plots were not sampled on the same days. cations where remnant MCH bubble capsule plastic is undesirable, and their retrieval is unfeasible. Bee Response to MCH in a Northern Rocky The potential for MCH treatments to repel forest pollinators Mountain Meadow Community was documented in the Syracuse Environmental Research Associates This experiment was conducted to directly assess any repellency ef- Risk Assessment submitted by the USDA Forest Service to the USEPA fects of MCH in the absence of potentially confounding factors asso- during registration of MCH, citing similarities in chemical structure ciated with variation in forest structure and composition within the between MCH and known chemical repellents of bees (Gupta et al. Douglas-fir forest experiment. The study site was located near the base 1989a, b; SERA 1999). However, no studies have tested for these of Mt. Ellis (45.629° N, 110.960° W; 1600–1700 m elevation) roughly potential interactions between MCH and wild bees. To determine 5 km southeast of Bozeman, Montana, USA. Experimental plots were any significant difference in overall bee abundance, species richness, in a large and diverse meadow community containing approximately or diversity between MCH-treated versus untreated areas, bees were 50 flowering plant species and more than 70 native bee species (Burkle sampled in summer 2016 on research plots comparing bubble cap- and Runyon 2016). The experimental design was completely random- sule and SPLAT formulations of MCH in a Douglas-fir forest in ized with three treatments and 10 replicates per treatment, randomly Idaho, USA. During the same summer in a companion experiment, assigned to stakes in two parallel N–S transects spaced 300 m apart, bee response to MCH was evaluated in a Northern Rocky Mountain each with 15 stakes spaced 50 m apart. Treatments assigned to the meadow community in Montana, USA, where the pollinator com- stakes were a blank bubble capsule (no MCH), one MCH bubble munity had been previously documented (Burkle and Runyon 2016). capsule (same product as described above), and one 10-g dollop of Sampling at this site allowed for detection of any changes in the bee SPLAT MCH. Blank bubble capsules were used as negative controls community directly due to the presence of MCH, without the poten- to account for any effects the plastic used to contain MCH may have tial confounding factors associated with variable forest stand struc- had on local bees.