Eryngium Stem Borer

Stem borer moths are declining due to habitat loss, pesticide use, and habitat fragmentation. Of the 35 stem borer species in Illinois, 10 are on the Watch List, 8 are SGCN, 1 is state-threatened, and 1 is potentially extinct. The remaining 15 species have yet to be assessed for conservation status. Once thought to be extinct in Illinois, the Rattlesnake Master (Eryngium) Stem Borer (ESB) was rediscovered in 1989 and subsequently listed as state-threatened.

Our project assesses populations and examines the genetic diversity and structure of the ESB across the species’ known range, informing management decisions. We assessed ESB populations and their host plant, Rattlesnake Master, at 10 grassland sites in central and southern Illinois and ESB  populations in sand prairies of Will County.

Field of Eryngium yuccifolium – Rattlesnake Master – being surveyed for stem borers

We conduct larval surveys in July when larvae are actively consuming their host plants. We examined  Rattlesnake Master plants for larval damage and extracted the larvae for identification. We measured the characteristics of individual plants hosting ESB larvae to determine the ideal host plant size and ESB’s potential impact.

We also used UV light traps in September to catch flying adult moths.

Papaipema eryngii caterpillar

On a broader scale, we are examining the phylogenetic structure of species within the genus, emphasizing the ESB. Learn more