LAUSR

Abstract Nuts from hybrid hazels (Corylus americana Walter × Corylus avellana L.) are a burgeoning, novel industry for the Great Lakes region of the United States. As such, scant information exists about the pest complex, although stem-boring beetles in the genus Agrilus Curtis (Coleoptera: Buprestidae) have been noted by growers as potential pests. Here, we report results of a comprehensive survey of 186 plants in a hybrid hazel planting consisting of nine cultivars in southeastern Minnesota affected by stem borers. Sixteen percent of the hybrid hazel plants exhibited between 25 and 100% buprestid associated dieback. Morphological and molecular identification of the adult and larval buprestids colonizing hybrid hazel plants revealed that the hazel stem borer, Agrilus pseudocoryli Fisher, was the only species present. Adult A. pseudocoryli were observed on plants between 8 June and 13 July 2021. Plants with higher damage ratings from the hazel stem borer were more likely to exhibit signs of eastern filbert blight (Anisogramma anomala Peck), a fungal pathogen virulent to C. avellana. Some hazel cultivars were more susceptible to damage from stem borers than others.Taken together, our findings suggest that the hazel stem borer has the potential to impact hybrid hazelnut yield.We speculate that a regional drought may have promoted increased populations of the hazel stem borer, as native Agrilus species are often secondary pests that become problematic when environmental stresses decrease host resistance. More research is needed to elucidate interactions between hazels, buprestid pests, and environmental conditions to predict impacts on crop yields.