Predicting the vulnerability of New Zealand radiata pine plantations to the European pine weevil

Abstract

Summary The European pine weevil, Hylobius abietis, is an important pest of temperate conifers and a significant biosecurity threat to countries such as New Zealand (NZ) where commercial forestry is largely dependent on pine monoculture. The economic impact of this insect is determined by its abundance and the degree of resistance of young pines to adult feeding. Assessing the likely impact of pine weevil in the event of accidental introduction is an important part of contingency planning. Resistance of 1- to 2-year-old trees was assessed by measuring the size of resin ducts within bark of the main stem and the mass of resin flowing from simulated feeding damage. Resin flow relative to duct area was much lower in radiata pine than in Corsican pines that are resistant to weevil feeding in the uK, indicating that NZ radiata pine transplants are likely to be highly susceptible. Local population size is influenced by the availability of pine root stumps after clearfelling. The short rotation of radiata pine and a likely shorter weevil generation time could increase weevil abundance and damage relative to the uK. however, larvae are likely to face competition from previously introduced bark beetles, and possibly native fungi, that rapidly exploit the bark of root stumps after felling. In particular, competition with Hylurgus ligniperda, which has an early spring flight and potential for two generations per year, is likely to reduce the number of weevils emerging from root stumps. Overall, pine weevil is likely to have less economic impact in NZ than in northern Europe.