Area-Wide Efficacy of a Localized Forest Pest Management Practice

Abstract

Few experimental studies have examined the movement of forest pest populations, particularly in response to management tactics that disrupt the growth of pest infestations. We quantified the interinfestation patterns of dispersal of the southern pine beetle, Dendroctonus frontalis Zimmermann (Coleoptera: Scolytidae), by monitoring the fates of fluorescently marked beetles after emergence from small natural infestations. Dispersal patterns from 3 untreated infestations were compared with those from 6 infestations treated with the widely used disruption suppression tactic, cut-and-leave (infested trees are felled and left in the forest). Among untreated infestations, 10 ± 4% (±1 SE) of the marked beetles were successful in colonizing experimentally created infestations located 100-500 m away. The highest proportion of marked beetles was recaptured at the nearest experimental infestations (at 100 m) and recaptures declined precipitously with distance from the source. Dispersal by beetles emerging from disrupted infestations showed a similar pattern to untreated infestations with respect to distance, but a much greater fraction of the beetles were recaptured at each distance. Overall, colonization success for treated infestations was 37 ± 6%, almost a 4-fold increase over untreated infestations. This suggests that by altering the dispersal patterns of beetles, the cut-and-leave suppression tactic may favor increased densities of flying beetles, and possibly more infested timber, in the surrounding region. Effective control of mobile pests may be enhanced by expanding our spatial scope and seeking to maximize the area-wide, not just the local, efficacy of management tactics.