Long-term monitoring and response of Papaipema sciata Bird (Lepidoptera: Noctuidae) to prescribed fire in Michigan (USA)

Abstract

The Culver’s root borer moth ( Papaipema sciata ) (Lepidoptera: Noctuidae) is a rare Noctuid that requires Culver’s root ( Veronicastrum virginicum ) to complete its lifecycle within remnant native grasslands and open woodlands in the midwest and northeast United States. We report on 26 years of monitoring this species’ colonization of Culver’s root stems at Algonac State Park (ASP) in Michigan, where prairies have been maintained by prescribed fire since 1990. P. sciata is considered fire sensitive because eggs spend the dormant season in the combustible prairie litter and duff near host plants. The objectives were to determine the effect of prescribed burns, burn unit size, and local precipitation on P. sciata population size and abundance of host plant V. virginicum . The moth has one generation per year and exhibits low dispersal capabilities—traits which presumably inhibit recolonization of burned areas, particularly when they are patchy, fragmented, and separated by closed canopy forest or agricultural lands. P. sciata colonization (defined as the proportion of V. virginicum plants hosting larvae) and total V. virginicum stems, though spatially and temporally variable, appear stable. Our results suggest that P. sciata abundance increases when managers lengthen the time interval between fires in a given burn unit, but this effect appears to diminish after three years. We also found precipitation during the adult (egg-laying) phase of P. sciata ’s life-cycle is positively associated with colonization rate, while the inverse was true for annual cumulative precipitation across all life cycle phases. We did not find evidence that colonization rate increased with increasing host plant abundance, indicating that host plant population size is not a suitable proxy to assess population size of the moth. The data also support current temporal guidance regarding prescribed fire and Papaipema at ASP.