Fraxinus pennsylvanica

As treated here (following Kartesz 1994 and 1999 and many other recent authors), includes both the "red ash" (Fraxinus pennsylvanica, in a narrower sense, of many older works) and the "green ash" (Fraxinus lanceolata of older works). LEM 14Jun00.

Fraxinus pennsylvanica occurs in Eastern North America from Florida and Texas north to Nova Scotia and Quebec; extending from the east, west to southeastern Alberta, Montana, Wyoming, Utah, and Texas. While the species is wide ranging and has many occurrences, it is suffering serious mortality due to the Emerald Ash Borer and has poor regeneration post infestation. Within six years of an invasion, the species can experience a nearly 100% decline with minimal regeneration. The Conservation Status of this species should be reviewed frequently to detect changes in the impact of the borer.

Fraxinus pennsylvanica occurs in Eastern North America from Florida and Texas north to Nova Scotia and Quebec; extending from the east, west to southeastern Alberta, Montana, Wyoming, Utah, and Texas (Gleason and Cronquist 1991). It may also occur southward into Mexico (GBIF 2019; iNaturalist 2019; SEINet 2019).

The number of occurrences is not known but is well over 300 based on specimen collections and photo based observations.

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, Steiner et al. 2019). Green ash appears to suffer the greatest mortality and least regeneration post-invasion (Robinett and McCullough 2019). 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. Emerald Ash Borer has been reported in most states and provinces where this species occurs (Emerald Ash Borer Information Network 2020).
Several diseases afflict Fraxinus pennsylvanicus: 1.) Mycosphaerella fraxinicola, a leaf spot causing premature defoliation in young trees, 2.) Anthracnose (Gleosproium aridum) that also causes premature defoliation, especially in wet years, 3.) a petiole and twig distorting rust, Puccinia peridermiopora, 4.) Fomes fraxinophilus, the white-mottled heartwood rot, and 5.) root rot caused by Phymatotrichum omnivorum.