D3089: Phenology and genotypic preferences of Polydrusus spp. in hazel plants (Corylus spp.) in the Upper Midwest

The Polydrusus species complex (Coleoptera: Curculionidae) in the United States contains seven species, two of which are introduced from Europe. Hybrid hazels are a novel crop being developed for production in the American Midwest that aims to blend the nut quality and yield of European hazelnut (Corylus avellana) with the cold hardiness and disease resistance of American hazelnut (Corylus americana Marshall). Both P. impressifrons Gyllenhal and P. formosa (Mayer) are introduced species that have recently been found on the hybrid hazels in the Midwest. These insects may pose a threat to the burgeoning hazelnut industry, as adults of both Polydrusus spp. have been known to damage buds and foliage of fruit trees and hardwoods. We elucidated the seasonal phenology of adult Polydrusus spp. on hybrid hazels in plantings in Minnesota over a two year period via beat-sheet sampling. We also measured temperature and relative humidity via data-loggers. Adult Polydrusus began emerging in late May of each year and their numbers continued until mid July. We found higher numbers of P. formosus than P. impressifrons in both years and higher numbers of males than females in 2020. This work will form a baseline for understanding occurrence Polydrusus spp. on hazel plants in the Midwestern US.