Spatio-temporal dynamics of an Ips acuminatus outbreak and implications for management

Authors

  • Fernanda Colombari,

    Corresponding author
    1. Department of Agronomy Food Natural resources Animals and Environment-DAFNAE, Università di Padova, Viale dell’Università, 16-35020 Legnaro, Italy
      Fernanda Colombari. Tel.: +39 049 8272807; fax: +39 049 8272810; e-mail: fernanda.colombari@unipd.it
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  • Martin L. Schroeder,

    1. Department of Ecology, Swedish University of Agricultural Sciences, PO Box 7044, S-750 07 Uppsala, Sweden
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  • Andrea Battisti,

    1. Department of Agronomy Food Natural resources Animals and Environment-DAFNAE, Università di Padova, Viale dell’Università, 16-35020 Legnaro, Italy
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  • Massimo Faccoli

    1. Department of Agronomy Food Natural resources Animals and Environment-DAFNAE, Università di Padova, Viale dell’Università, 16-35020 Legnaro, Italy
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Fernanda Colombari. Tel.: +39 049 8272807; fax: +39 049 8272810; e-mail: fernanda.colombari@unipd.it

Abstract

  • 1Understanding spatio-temporal processes of bark beetle infestations is crucial for predicting beetle behaviour and aiding management decisions aiming to prevent or mitigate tree mortality. We recorded the spatial and temporal distribution of killed trees during the 5-year period of an Ips acuminatus outbreak.
  • 2Killed trees were always grouped in well-defined patches (infestation spots). In years of high population density, infestation spots were large and aggregated, whereas, in years of low density, infestation spots were small and weakly aggregated or randomly distributed within the study area.
  • 3Most trees were killed in the spring by beetles that had hibernated but, in some years, trees were also killed in the summer by new-generation beetles originating from spring attacks. Spring-killed trees always formed new infestation spots at new locations (i.e. spot proliferation). By contrast, summer-killed trees always occurred at the edge of active spots established in the spring, thus resulting in spot growth.
  • 4With regard to management strategies, the results obtained in the present study suggest that areas located in close proximity to infestations of the previous year should be prioritized for risk assessment. Because large spots account for most of the observed tree mortality, the cut-and-remove method should be focused on these spots as soon as crown discoloration appears in the summer. If applied timely, this strategy will remove the new-generation beetles originating from the spring attacks before they emerge and also reduce the risk of spot growth.

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