Climate Risk Modelling of Balsam Woolly Adelgid Damage Severity in Subalpine Fir Stands of Western North America

Abstract

The balsam woolly adelgid (Adelges piceae (Ratzeburg) (Homoptera: Adelgidae)) (BWA) is a nonnative, invasive insect that threatens Abies species throughout North America. It is well established in the Pacific Northwest, but continues to move eastward through Idaho and into Montana and potentially threatens subalpine fir to the south in the central and southern Rocky Mountains. We developed a climatic risk model and map that predicts BWA impacts to subalpine fir using a two-step process. Using 30-year monthly climate normals from sites with quantitatively derived BWA damage severity index values, we built a regression model that significantly explained insect damage. The sites were grouped into two distinct damage categories (high damage and mortality versus little or no mortality and low damage) and the model estimates for each group were used to designate distinct value ranges for four climatic risk categories: minimal, low, moderate, and high. We then calculated model estimates for each cell of a 4-kilometer resolution climate raster and mapped the risk categories over the entire range of subalpine fir in the western United States. The spatial variation of risk classes indicates a gradient of climatic susceptibility generally decreasing from the Olympic Peninsula in Washington and the Cascade Range in Oregon and Washington moving eastward, with the exception of some high risk areas in northern Idaho and western Montana. There is also a pattern of decreasing climatic susceptibility from north to south in the Rocky Mountains. Our study provides an initial step for modeling the relationship between climate and BWA damage severity across the range of subalpine fir. We showed that September minimum temperature and a metric calculated as the maximum May temperature divided by total May precipitation were the best climatic predictors of BWA severity. Although winter cold temperatures and summer heat have been shown to influence BWA impacts in other locations, these variables were not as predictive as spring and fall conditions in the Pacific Northwest.

Using Remote Sensing and Climate Data to Map the Extent and Severity of Balsam Woolly Adelgid Infestation in Northern Utah, USA

“…If remote sensing alone is insufficient for mapping BWA to a desirable degree of accuracy and precision, then perhaps additional geospatial data can augment the analysis. BWA damage has been shown to be strongly temperature-and terrain-dependent [10,[37][38][39][40][41][42]. Although many have noted this dependency, few have exploited it for mapping purposes.…”

“…Although many have noted this dependency, few have exploited it for mapping purposes. Hrinkevich et al [39] compared plot-level BWA infestation severity to a suite of climate variables derived from PRISM data [43], finding summer and autumn temperature-related variables to be particularly important in predicting severity. This study provides evidence of the potential benefit of utilizing spatial data representing abiotic environmental factors, but the predictive power of their models was fairly low (R 2 = 0.24), and their results were generated at a relatively coarse spatial resolution (4 km).…”

The Vision of Managing for Pest-Resistant Landscapes: Realistic or Utopic?

“…Stress conditions (drought, fire, cutting, etc.) (Gottschalk, 1993) Oak processionary moth ( Thaumetopoea processionea ) Oak trees ( Quercus sp) (Godefroid et al 2012) Reduce oak monocultures (Castagneyrol et al 2012) Range expansion throughout much of Europe Increase in frequency and severity in Central Europe (Groenen & Meurisse 2012) Climatic suitability, plus abundant oak in new ranges (Groenen & Meurisse 2012, Godefroid et al 2020) Larch casebearer ( Coleophora laricella ) Larches from all age classes in pure and mixed stands (Tabakovic-Tosic et al , 2011) Cutting branches above 1.3m may help (Ward & Aukema, 2019) Quebec, late 1970s population infestation caused severe defoliation (Langor et al , 2014) Climatic suitability (dry warm) (Tabakovic-Tosic et al , 2011) (Ward & Aukema, 2019) Balsam woolly adelgid ( Adelges piceae ) Fir ( Abies ) species (Hrinkevich, et al 2017) Regulations restricting wood movement from infested areas (Hrinkevich, et al 2017) Recent outbreak in 2014 (Hrinkevich,et al, 2017) Varies by site quality and species of fir (Hrinkevich et al 2016) References: Björklund and Lindgren [ 178 ], Bognounou [ 61 ••], Cooke et al [ 24 ], Creeden et al [ 179 ], Fettig et al [ 45 ], Gottschalk [ 180 ], Gottschalk et al [ 181 ], Hrinkevich et al [ 182 ], Hrinkevich et al [ 183 ], Jenkins et al [ 184 ], Johns et al[ 43 ], Langor et al [ 185 ], Man et al [ 186 ], Mezei et al [ 22 ], Raffa et al [ 20 ], Roland [ 106 ], Safranyik and Carroll [ 192 ], Sharov and Liebhold [ 187 ], Tabakovic-Tosic et al [ 188 ], Taylor et al [ 189 ], Uelmen et al [ 190 ], Ward and Aukema [ 191 ], Wermelinger [ 35 ] …”

“… References: Björklund and Lindgren [ 178 ], Bognounou [ 61 ••], Cooke et al [ 24 ], Creeden et al [ 179 ], Fettig et al [ 45 ], Gottschalk [ 180 ], Gottschalk et al [ 181 ], Hrinkevich et al [ 182 ], Hrinkevich et al [ 183 ], Jenkins et al [ 184 ], Johns et al[ 43 ], Langor et al [ 185 ], Man et al [ 186 ], Mezei et al [ 22 ], Raffa et al [ 20 ], Roland [ 106 ], Safranyik and Carroll [ 192 ], Sharov and Liebhold [ 187 ], Tabakovic-Tosic et al [ 188 ], Taylor et al [ 189 ], Uelmen et al [ 190 ], Ward and Aukema [ 191 ], Wermelinger [ 35 ] …”

Evolutionary recent dual obligatory symbiosis among adelgids indicates a transition between fungus and insect associated lifestyles

“…The group has nearly seventy species and is sister to the families of phylloxerans (Phylloxeridae) and aphids (Aphididae) within the suborder Sternorrhyncha (6). Some adelgid species, such as the balsam woolly adelgid (Adelges piceae) and the hemlock woolly adelgid (A. tsugae) are well-known forest pests and represent severe threats to firs and hemlocks (7,8).…”