Trap Catch Data are Poor Predictors of Damage Caused by Pine Weevil (Hylobius Abietis) to Conifer Seedlings

Evaluation of trap type and attractant composition for potential mass trapping of Hylobius abietis

“…Estimations of population sizes on regeneration sites of harvested coniferous stands range from 14,000 individuals per hectare in the parent generation up to 220,000 individuals per hectare including potentially emerging young H. abietis (Leather et al, 1995; Moore et al, 2003; Nordlander, Bylund, et al, 2003). Even though the data of this study implies an effective reduction of the local H. abietis population, this assumption cannot be verified exclusively based on the number of trapped individuals, which is also stressed by Nordlander et al (2023).…”

“…It is debatable whether a local population reduction of H. abietis by trapping is possible (Fedderwitz et al, 2022; Olenici et al, 2016). A recent study by Nordlander et al (2023) did not find a relationship between trap catch data and damage on seedlings, implying that other factors than the population size determine the extent of seedling damage. Alternative food sources reduce the attractivity of traps, hence complex attractant combinations are necessary, which can compete with other food sources on the regeneration site.…”

“…Population densities are estimated to rise up to 220,000 individuals per hectare, but also at low population densities, H. abietis is able to cause severe damage (Inward et al, 2012; Leather et al, 1995). There is furthermore strong evidence that damage on regeneration sites is not mainly influenced by the population size but strongly by the availability of alternative food sources such as roots of living trees and branches (Nordlander et al, 2023; Nordlander, Bylund, et al, 2003; Nordlander, Orlander, & Langvall, 2003) increasing the complexity of mass trapping efforts. Consequential highly attractive lures applied in effective trap systems are necessary to locally and temporarily reduce the population densities of the target insects in a way that secures the economic and ecological goals of the forest owners.…”