Minimum Winter Temperature as a Limiting Factor of the Potential Spread of Agrilus planipennis, an Alien Pest of Ash Trees, in Europe

Abstract

The emerald ash borer, EAB (Agrilus planipennis) is a devastating alien pest of ash trees. It is spreading in European Russia and Ukraine and will appear in other European countries. Our aim was to determine the regions of Europe where the winter temperature drops low enough to prevent A. planipennis establishment. We calculated the minimum daily air temperature from 2003–2019 for each grid square (0.5° × 0.5°) in East Asia, North America and Europe and determined the minimum daily temperature in the grid squares where A. planipennis was recorded. Temperatures of −30 to −33 °C occur in the northern portions of the pest range on all continents. No established population has been recorded in localities where temperatures below −34 °C occur. This temperature is close to the absolute supercooling point of A. planipennis larva (−35.3 °C). It is unlikely that low temperatures could prevent the spread of A. planipennis in northern Western Europe (Sweden, Norway, Finland, etc.), since the temperature in this area did not fall to −34 °C from 2003–2019. However, such temperatures are not rare in eastern European Russia (Kostroma, Vologda, Orenburg regions, etc.), where Fraxinus pennsylvanica and F. excelsior occur. These regions could potentially become refuges for these ash species.

Invasive Populations of the Emerald Ash Borer Agrilus planipennis Fairmaire, 1888 (Coleoptera: Buprestidae) in Saint Petersburg, Russia: A Hitchhiker?

“…Another indication of the low suitability of the Saint Petersburg area for the development of populations of EAB is the fact that none of the F. pennsylvanica trees attacked during the first infestation wave in 2015-2018 has been killed, thus surviving to the second infestation wave of 2019-2020. The most likely explanation for the restricted EAB spread is climatic factors, in particular low winter temperatures [5,14].…”

North-Westward Expansion of the Invasive Range of Emerald Ash Borer, Agrilus planipennis Fairmaire (Coleoptera: Buprestidae) towards the EU: From Moscow to Saint Petersburg

“…Temperature has been reported to be a limiting factor of spread of A. planipennis [21] and references therein. Not surprisingly, therefore, notably more efficient rates of "natural" expansion have been observed of invasive European EAB populations approx.…”

Invasive Populations of Emerald Ash Borer <em>Agrilus planipennis</em> Fairmaire, 1888 (Coleoptera: Buprestidae) in Saint Petersburg, Russia: a “Hitchhiker”?

“…Absolute annual minimal temperatures below -30°С are seemingly critical for the survival of EAB population, and isotherm of absolute minimum of -34°С is apparently the climatic boundary for the area of EAB distribution [5,12]. In Saint Petersburg, despite the generally continuous trend of climate warming, such critically low temperatures were observed in the last century (e.g., in 1987), yet also during 2000s absolute yearly minimum at several instances has decreased to almost -30°С (Figure 4).…”