Evaluation

Bolts were evaluated at 2, 6, and 14 d for trial 1, and 2, 7, and 14 d in trial 2. There was a heavy rain forecast on the fifth day of trial 2 (Supplementary Fig. 1), which may have affected beetle flight and their interactions with the bolts. The cumulative number of ambrosia beetle entry holes on the bolts was quantified at each evaluation date. The entry holes were circled using a different colored wax pencil at each check date to avoid double counting. Beetles that bored into the bolts were not excised. All ambrosia beetles stuck on the glue were counted at each evaluation day post-treatment. At the end of the trial, all bolts were collected and placed in plastic bags, transported to the laboratory, and stored in a freezer at −18°C until processing. All ambrosia beetles, including non-Xylosandrus spp., were counted, as identifying them was challenging in the field. The cumulative data up to the 14 d check date are presented by adding the number of beetles in the glue, the number of beetles in the pail (in soap), and the number of entry holes up to 14 d post-treatment.

Before processing, bolts were allowed to thaw at 21°C for 2 h. The ambrosia beetles caught on the glue were removed from the bolts by painting Histo-Clear (Electron Microscopy Sciences, Hatfield, Pennsylvania, USA) onto the glue with a paintbrush. After 2 min, ambrosia beetles loosen enough to be removed using pointed forceps. The removed adults were placed into a vial filled with 10 ml of Histo-Clear. After 15 h in the solvent, adults were rinsed in water and 70% ethanol before storage in a vial with 70% ethanol for identification at a later date. Those ambrosia beetles inside the galleries within the bolts were not extracted.

Adult ambrosia beetles collected in soapy water under the bolts were screened by pouring it through a mesh bag and recovering the contents at the 3 evaluation dates. From filtered samples, the ambrosia beetles were sorted and removed using a paintbrush and stored in microcentrifuge tubes filled with 70% ethanol for identification. In a few cases, soap samples of individual bolts were lost due to rain, and sustained wind. Those samples were considered missing data points. Ambrosia beetles were stored in ethanol and then identified at a later date. Beetles were identified to species using Bateman and Hulcr’s guide to bark and ambrosia beetles (Bateman and Hulcr 2017). Xylosandrus were identified to species, with all other ambrosia beetle genera being grouped into the “other” category. Thus, Xylosandrus was presented as the primary genus of concern for southeastern ornamental nurseries (Ranger et al. 2016b, Gugliuzzo et al. 2021, Monterrosa et al. 2022).