Full PDF

Wagner, D.L. and K. Todd. 2015. Ecological impacts of the emerald ash borer. Pp. 15-62. In: R.G. Van Driesche (ed.), Biology and Control of Emerald Ash Borer, USDA Technical Bulletin FHTET-2014-09. Morgantown, WV.

EFFECTS ON ASH-FEEDING INVERTEBRATES

We identify 98 Fraxinus-dependent invertebrate herbivores (or inquilines) as potentially threatened by the spread of EAB, 45 of which are reported here for the first time (Figs. 13-20). Because our compilation of Fraxinus feeders was a bottom-up tabulation for all insects and mites, built upon the collective knowledge of more than 80 taxonomic experts, we feel the data in Table 4 offer a unique look at the taxonomic distribution of ash-specialist herbivores from the estimated 70,000 species of North American insects (Arnett, 2000) and Acari (mites).

Specialist herbivores that would be imperiled or extirpated in the United States and Canada by the loss of Fraxinus include mites (n = 6) and members of five insect orders: Lepidoptera (n = 32), Hemiptera (n = 25), Coleoptera (n = 24), Diptera (n = 9), and Hymenoptera (n = 3) (Fig. 21). The most speciose lineage of metazoans on the planet, beetles, had fewer specialists than Lepidoptera and essentially equivalent richness to that of Hemiptera. While the focal taxon of our study was Fraxinus and related Oleaceae, we suspect that the proportions represented here are likely to apply across most temperate woody, broadleaf plant taxa, and may well apply to other continental biogeographic provinces as well.

Four genera contain six or more species that will be threatened by the spread of EAB; in decreasing diversity these include:

Tropidosteptes plant bugs (Miridae) (n = 14) (Fig. 13),
Hylesinus bark beetles (Curculionidae) (n = 7),
Lignyodes seed weevils (Curculionidae) (n = 7) (Fig. 19), and
Sphinx hawkmoths (n = 6) (Sphingidae) (Figs. 16, 17).

Four other genera contain noteworthy radiations on Fraxinus:

Dasineura gall midges (Cecidomyiidae),
Prociphilus aphids (Aphididae),
Philtraea inchworms (Geometridae) (Fig. 15), and
Sympistis sallows (Noctuidae).

For these herbivores we estimate endangerment risks as

Very High (n = 5),
High (n = 75),
High to Moderate (n = 15), and
Moderate (n = 3) (Fig. 21).

The Very High risk rating – given to just five lepidopterans – was reserved for ash specialists believed to be at risk or in decline due to other causes. Marmara basidendroca and M. corticola (both Gracillariidae) are both specialized stem miners known only from a restricted area in Upstate New York. Philtraea latifoliae (Geometridae) feeds exclusively on Fraxinus latifolia and is known only from a few counties in central California (Buckett, 1970). Sphinx canadensis’ rating was raised to Very High because it is principally associated with F. nigra, an ash that is highly susceptible to EAB infestation (Leah Bauer pers. comm.) and which is predicted to be increasingly at risk due to climate change (Liang and Fei, 2014). Sphinx franckii is already uncommon and northern populations are in decline (Wagner, 2012).

Buckett, J.S. 1970. Revision of the Nearctic genus Philtraea Hulst, with notes on biology and the description of new species (Geometridae). Journal of Research on the Lepidoptera 9: 29–64.
Wagner, D.L. 2012. Moth decline in the northeastern United States. News of the Lepidopterists’ Society 54: 52–56.