Evaluating the establishment potential of cabbage stem flea beetle (Coleoptera: Chrysomelidae) and pollen beetle (Coleoptera: Nitidulidae) in canola-growing regions of North America using ensemble species distribution models.

Abstract

Cabbage stem flea beetle, Psylliodes chrysocephala (Linnaeus 1758), and pollen beetle, Brassicogethes viridescens (Fabricius 1787), are pests of oilseed rape [Brassica spp. (Brassicales: Brassicaceae)] crops in Europe and pose a potential threat to canola production in North America. We used species occurrence and environmental data to develop ensemble species distribution models describing P. chrysocephala and B. viridescens habitat suitability, creating risk maps for either species under current (1981-2010; globally) and future [2011-2040 and 2041-2070, across 2 IPCC Shared Socio-economic Pathways (SSPs); North America only] environmental conditions. Projections for both species show improvement in northern North American habitat suitability under either SSP over time. Crop dominance was the most important predictor of suitable habitat for both species, followed by mean annual temperature range, precipitation metrics, and elevation (P. chrysocephala only). Risk maps for P. chrysocephala show broad habitat suitability, increasing under future scenarios, for this insect if it becomes introduced to North America; however, a phenological mismatch between P. chrysocephala, which specializes on winter oilseed rape (WOSR) in Europe, and spring oilseed rape (SOSR) would likely inhibit the long-term persistence of this insect in central North America. For B. viridescens, which impacts SOSR in Europe and is present in northeastern North America, predictive maps show increased risk in discontinuous patches across central North America that improve in suitability over time. While SOSR-cropping systems in central North America are environmentally suitable for both P. chrysocephala and B. viridescens, the establishment potential of these species may depend upon future sowing practices.