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-endangered.
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. We conducted 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 also used UV light traps in September to catch flying adult moths. We measured the characteristics of individual plants hosting ESB larvae to determine the ideal host plant size and ESB’s potential impact.
On a broader scale, we are examining the phylogenetic structure of species within the genus, emphasizing the ESB. Determining the distribution and relationships of stem borer moth species is difficult but important for meaningful conservation measures to be enacted. The project will include previously collected samples of stem borers from Illinois, Missouri, Arkansas, Oklahoma, Kentucky, and North Carolina. Our work will most broadly examine the phylogenetic structure of species within the genus, emphasizing the ESB. We have extracted and amplified DNA from the legs of over 125 individual stem borer moths and are analyzing the genetic sequences we have obtained.