Flight activity of wood- and bark-boring insects at New Zealand ports

Background: Bark- and wood-boring forest insects spread via international trade. Surveys frequently target new arrivals to mitigate establishment. Alternatively, monitoring pest activity in exporting countries can inform arrival and establishmentrisk. Methods: We report >3 years data from daily sampling of bark- and wood-boring insects that are associated with recently felled Pinus radiata D.Don at five New Zealand ports. Results: Average catch differed between ports and months with Arhopalus ferus (Mulsant), Hylurgus ligniperda F., and Hylastes ater (Paykull) comprising 99.6% of the total catch. Arhopalus ferus was absent during winter with Hylastes ater and Hylurgus ligniperda activity between June and August representing 3.5 and 3.7% of total catch, respectively. Maximum temperature and wind speed influenced flight activity of all three species but not universally across all ports. Flight activity transitioned to a nonlinear pattern above 20°C. Arhopalus ferus has a unimodal flight risk period between late-September and late-April. Hylastes ater was also unimodal except in Dunedin where it was bimodal like Hylurgus ligniperda was in all regions with spring and mid- to late-summer activity periods. Although Hylastes ater was observed during winter, the probability of a flight event during winter was between 0 and 0.02 per week. Hylurgus ligniperda flight probability was zero in Dunedin and low at all other ports from May  to August. Conclusions: Modelling seasonal changes in flight probability can inform risk-based phytosanitary measures. We demonstrate the utility of maximum temperature and seasonality as a predictor of wood commodity infestation risk. Such predictors allow National Plant Protection Organisations to develop standards that protect the post-treatment phytosanitary security of individual consignments.