Professor University of Minnesota Saint Paul, Minnesota
The filbert or hazelnut big bud mite, Phytoptus avellanae, is a species of gall-mite introduced to the US from Europe that causes galls or “big buds” in floral and vegetative buds of species of hazel (Corylus). These plant deformities result in economic losses. Phytoptus avellanae has been confirmed in recently developed plantings of hybrid hazel (C. americana x C. avellana) in the Midwest, which is striving to establish a fledgling hazelnut industry. The mite is difficult to control due to the cryptic nature of its life cycle: the mite resides inside developing buds for most of the year except when it migrates to new axillary buds over the spring/summer. The timing and potential triggers of this movement are poorly understood. We monitored P. avellanae emergence from galls of infested hybrid hazels from four locations across the Midwest from mid-April through early July of 2019 and 2020 via sticky tape. Plant phenology characteristics such as normal bud size and number of emerged leaves per shoot were recorded weekly, and temperature and relative humidity were recorded every two hours. We utilized these data to build models to predict the movement of P. avellanae on hybrid hazels in relation to weather, plant phenology, and time. Our goals are to understand and eventually control this damaging pest. Developing forecasting models, especially for pests with long emergence periods, can help to reduce the number of chemical spray treatments needed for control.
