Phenological observations and trapping tactics for the granulate ambrosia beetle Xylosandrus crassiusculus (Coleoptera: Curculionidae, Scolytinae) in New Zealand

Abstract

Abstract The granulate ambrosia beetle (GAB) Xylosandrus crassiusculus, was first formally detected in New Zealand in 2019. Since then, GAB has subsequently been found infesting numerous tree species in the Auckland region. Flight intercept traps baited with ethanol lures were deployed from October 2019 to May 2021 at three sites in the Auckland region to ascertain the phenology of GAB in New Zealand. Two distinct peak flight periods were identified in early and late summer, while a smaller and inconsistent third peak was detected in early autumn. Logistical analysis of GAB captures in the ethanol‐lured traps and degree‐day (DD) accumulation indicated that 90% of flight activity is completed by 800 DD. To assess monitoring tactics, flight intercept traps were baited with three different ethanol lures with varying release rates or ethanol‐soaked or non‐soaked wood bolts from three species of trees. A lure releasing 2 g ethanol per day was most effective at capturing GAB. Ethanol‐soaked bolts were less effective than the lures. Xylosandrus crassiusculus represents a significant risk for shrubs and trees native to New Zealand, as well as commercial horticultural and forestry trees. We recommend using ethanol‐lured panel traps for monitoring purposes.