Examination of dogbane beetle (Chrysochus auratus) feeding and phenology on spreading dogbane, and considerations for biological control

Abstract

We carried out experiments that considered the feeding, phenology, and biocontrol potential of dogbane beetle, Chrysochus auratus, on spreading dogbane, Apocynum androsaemifolium, a native perennial weed in lowbush blueberry (Vaccinium angustifolium). In no-choice host-feeding experiments, adult beetles did not feed upon common milkweed (Asclepias syriaca), periwinkle (Vinca minor), wild raisin (Viburnum cassenoides), and lowbush blueberry, all plants related to spreading dogbane or found around lowbush blueberry fields. In a field experiment, significant decreases in spreading dogbane total and foliar weight occurred at a density of 16 beetles per ramet, but not at lower beetle densities. In our Nova Scotia (NS) field sites, beetles were present for 8–12 weeks, beginning in late June or early July (225–335 growing degree days, GDD). Beetle abundance peaked at 4–7 beetles/m2 and occurred at 357–577 GDD, which temporally coincides with the incidence of mature spreading dogbane plants in the field. The results suggest that although inundations of C. auratus could cause significant defoliation of spreading dogbane, natural populations of the beetle probably could not satisfactorily suppress development of this weed as a stand-alone control tactic. Conservation and augmentation of C. auratus populations should nonetheless be encouraged in integrated management programs for spreading dogbane.