Large-scale, multi-year, phenology modelling of forest insects in Pinus radiata plantations

Abstract

Ecologically and economically harmful wood borers and bark beetles, which have the capacity to expand geographically through the international log trade, require mitigations to prevent their spread. Detailed phenological knowledge of these pests across the wood-product supply chain can support systems approaches to phytosanitary risk management. Forest insect activity from 3.5 years of monthly, fortnightly, and daily sampling in recent clearfells from eight Pinus radiata plantation regions throughout New Zealand is presented. Phenology varied regionally with some species absent from specific regions. Insect activity declined with postharvest duration to a hypothesised background activity level that may be determined by landscape dispersal processes. Maximum temperature was the strongest predictor of flight activity with a 15 °C threshold that increased the probability of flight. Probability of a flight event was calculated for each species at monthly, fortnightly, and daily periods. Although wintertime activity was low, operationally effective temporal periods of low pest prevalence could not be defined on a monthly basis. Assurance of temporal periods of low pest prevalence as part of a systems approach will require additional supporting evidence of the relationship between forecast weather on short temporal scales (days), the probability of flight, and the relationship between low-level flight activity and the risk of wood product infestation by dispersing insects.