Fraxinus quadrangulata

In a recent phylogenetic analysis Wallander (2008) determined that Fraxinus quadrangulata and Fraxinus anomala are united with Fraxinus dipetala in the section Dipetalae.

Fraxinus quadrangulata occurs in the east-central U.S.A. from western Ohio to Michigan, Indiana, and Illinois; south to northern Alabama, Missouri and northern Arkansas, and western Kansas. The primary threat to this species is mortality and reduced regeneration associated with the Emerald Ash Borer, a phloem-feeding beetle native to Asia. The Conservation Status of this species should be reviewed frequently to detect changes in the impact of the borer.

Fraxinus quadrangulata occurs in the east-central U.S.A. from western Ohio to Michigan, Indiana, and Illinois; south to northern Alabama, Missouri and northern Arkansas, and western Kansas. There are scattered occurrences at the perimeter of the species range (Ontario, Georgia, Virginia, West Virginia, and Oklahoma).

The primary threat to this species is mortality and reduced regeneration associated with the Emerald Ash Borer, a phloem-feeding beetle native to Asia. The invasive Emerald Ash Borer (EAB), Agrilus planipennis Fairmaire, 1888, was introduced in Detroit, Michigan from Asia in the 1990s (Haack et al. 2002) and has since caused rangewide declines in ash populations. The beetles feed on the leaves and lay their eggs in crevices of the bark. Larvae feed in the vascular structures during the summer, creating serpentine shaped galleries. They typically prepupae overwinter in the trees with pupation lasting from April-May, when adults emerge. Emerald Ash borers cause significant damage to the foliage of the tree and the vascular tissues. The tree will typically die within two years of the infestation (Poland and McCullough 2006). Within six years of an infestation, up to 99% mortality was observed in ash species (Knight et al. 2013, Klooster et al. 2014, McCullough et al. 2008). Tree saplings with 2 or more cm dbh can be infested (McCullough et al. 2008, Aubin et al. 2015). While an infested tree may push out root sprouts for one to two years, the tree usually dies (Klooster et al. 2014). The mass mortality of reproductively mature plants that would replenish the seed bank and the relatively short persistence in the seed bank (2-3(7) years) (Klooster et al. 2014), causes concern about the species ability to regenerate post-infestation. However, studies in southeastern Michigan report a lesser impact on Blue Ash than other species, with declines of 7.1% and 31.6% in the overstory. In addition, the species at sites in southeastern Michigan show abundant regeneration. (Spei 2016). Other studies in the region noted similar rates of decline, between 20% and 40% for Blue Ash (Tanis and McCullough 2012). Blue ash appears to be less susceptible to EAB; the bark thickness of this species is close to the maximum thickness that EAB can penetrate with its ovipositor (Peterson 2014).