Interspecific Variation in Resistance of Asian, European, and North American Birches (Betulaspp.) to Bronze Birch Borer (Coleoptera: Buprestidae)

Abstract

Bronze birch borer (Agrilus anxius Gory) is the key pest of birches (Betula spp.) in North America, several of which have been recommended for ornamental landscapes based on anecdotal reports of borer resistance that had not been confirmed experimentally. In a 20-yr common garden experiment initiated in 1979 in Ohio, North American birch species, including paper birch (Betula papyrifera Marshall), 'Whitespire' gray birch (Betula populifolia Marshall), and river birch (Betula nigra L.), were much more resistant to bronze birch borer than species indigenous to Europe and Asia, including European white birch (Betula pendula Roth), downy birch (Betula pubescens Ehrh.), monarch birch (Betula maximowicziana Regel), and Szechuan white birch (Betula szechuanica Jansson). Within 8 yr of planting, every European white, downy, and Szechuan birch had been colonized and killed, although 100% of monarch birch had been colonized and 88% of these plants were killed after nine years. Conversely, 97% of river birch, 76% of paper birch, and 73% Whitespire gray birch were alive 20 yr after planting, and river birch showed no evidence of colonization. This pattern is consistent with biogeographic theory of plant defense: North American birch species that share a coevolutionary history with bronze birch borer were much more resistant than naïve hosts endemic to Europe and Asia, possibly by virtue of evolution of targeted defenses. This information suggests that if bronze birch borer were introduced to Europe or Asia, it could threaten its hosts there on a continental scale. This study also exposed limitations of anecdotal observation as evidence of host plant resistance.

Inter- and Intra-Specific Variation in Stem Phloem Phenolics of Paper Birch (Betula papyrifera) and European White Birch (Betula pendula)

“…There is considerable interspecific variation in birch resistance to BBB (Nielsen et al, 2011). For example, species endemic to North America that have coevolved with BBB, such as paper birch (B. papyrifera Marshall), are highly resistant unless stressed (Balch and Prebble, 1940;Anderson, 1944;Barter, 1957;Jones et al, 1993).…”

“…For example, species endemic to North America that have coevolved with BBB, such as paper birch (B. papyrifera Marshall), are highly resistant unless stressed (Balch and Prebble, 1940;Anderson, 1944;Barter, 1957;Jones et al, 1993). In contrast, species alien to North America that do not share a coevolutionary history with BBB are much more susceptible (Ball and Simmons, 1980;Miller et al, 1991;Nielsen et al, 2011). For example, BBB colonizes and kills European white birch (B. pendula Roth) at much higher rates than paper birch (Ball and Simmons, 1980;Miller et al, 1991;Nielsen et al, 2011).…”

“…In contrast, species alien to North America that do not share a coevolutionary history with BBB are much more susceptible (Ball and Simmons, 1980;Miller et al, 1991;Nielsen et al, 2011). For example, BBB colonizes and kills European white birch (B. pendula Roth) at much higher rates than paper birch (Ball and Simmons, 1980;Miller et al, 1991;Nielsen et al, 2011). In a similar pattern, Asian species of ash (Fraxinus) that share an evolutionary history with emerald ash borer (A. planipennis Fairmaire), a congener to BBB, are more resistant to colonization by emerald ash borer than evolutionarily naïve North American ash species (Rebek et al, 2008).…”

“…Therefore, as a follow-up to the commongarden study of Nielsen et al (2011) that documented greater resistance to BBB in paper birch relative to European white birch, we initiated a study at the same site with the goal of elucidating potential mechanisms underlying variation in resistance. Specifically, we compared qualitative and quantitative differences in phenolic profiles of the stem phloem tissues of these two species.…”

Hybridisation, Introgression and Phylogeography of Icelandic Birch

“…Its timber is used commercially for veneer, pulpwood and many speciality items. Recent studies on this birch are focused on timber quality in relation to tree growth, browsing, soil fertility and other factors (Droulin et al 2010;Kleczewski et al 2010;Belleville et al 2011;Nielsen et al 2011;Rea 2011). Asiatic and subtropical birches, on the other hand, receive very little attention regarding silviculture, possibly due to the abundance and diversity of hardwood species that may be more valuable.…”