A time and place: Assessing the phenology of ambrosia beetles (Coleoptera: Curculionidae) to document and predict the occurrence of peaks of activity in nurseries

Ambrosia beetles are a key pest of ornamental trees, resulting in intensive management to meet growers’ zero--tolerance for damage. Females emerge from nearby woodlots in the spring and cue into ethanol that is emitted by physiologically stressed trees that may be growing in ornamental nurseries. After locating a host tree, beetles bore into the stem, creating holes that render the tree unmarketable. Growers apply pyrethroids before and during the peak flight activity to limit females from boring into trees. Annual variation in temperature and precipitation influence seasonal flight activity. Phenology data for several exotic species are needed so that the timing of pyrethroid applications coincides with peak activity. A phenological model would help to accurately predict peaks of activity in future years. Ethanol-baited traps and ethanol-infused wood bolts (30 cm length and 5 cm wide) were deployed across multiple sites in Virginia to document the quantity and diversity of adults captured, as well as the number of boring holes over a two-year period. Xylosandrus crassiusculus, X. germanus, Cnestus mutilatus, and X. compactus were the most common species in traps and bolts, with X. crassiusculus being the most abundant. Start of flight activity for X. crassiusculus was documented in March, with peaks in activity ranging from April 10 to May 22. Temperature and precipitation will be applied to this dataset to predict the peak flight activity each year. Models predicting the phenology of ambrosia beetles will help growers optimize their control tactics.