Fine fluorescent powder marking study of dispersal in the spruce bark beetle, Ips typographus (Coleoptera: Scolytidae)

Petr Dolezal,Marketa Davidkova,Jan Okrouhlik

doi:10.14411/eje.2016.001

Abstract

A novel method was used to study dispersal in the spruce bark beetle, Ips typographus (L.), under epidemic conditions (rapidly increasing population density) in the Sumava National Park. Infested spruce logs were coated with a fine fluorescent powder and the passively marked emerging beetles were captured in pheromone baited traps located at various distances from these logs. The number of marked beetles captured decreased exponentially with increasing distance from the release point. The sex ratio of the bark beetles was more female biased the further they were recaptured from the logs, being 57% and 60% at distances of up to 50 and 100 m, respectively. The maximum distance flown by a marked beetle recorded in this experiment was 1094 m. A model fitted to the data on dispersal indicates that 10% of the spruce bark beetles dispersed over distances of 55 m and 4 m in spring (overwintered parental generation) and summer (first filial generation), respectively. Differences between spring and summer swarming are briefly discussed.

Highlights

Even-aged monocultures of Norway spruce (Picea abies) are the main type of forests planted in the Czech Republic (Spiecker, 2003; Knoke et al, 2005; Yousefpour et al, 2010; Mansfeld, 2011)
The volume of infested timber is not being monitored due to the conservation status of the locality, but an indication of the population density of the spruce bark beetle can be obtained from the maximum yearly catches of monitoring pheromone traps that reached 50,000 to 150,000 beetles per trap in the period 2009– 2013
The adults of the filial generation were first caught at the end of July and a maximum number of almost 7000 beetles per trap per week (BTW) was recorded at the beginning of August

Summary

Introduction

Even-aged monocultures of Norway spruce (Picea abies) are the main type of forests planted in the Czech Republic (Spiecker, 2003; Knoke et al, 2005; Yousefpour et al, 2010; Mansfeld, 2011). The final acceptance of a host spruce tree is probably further conditioned by visual signals, which may (in some bark beetle species) prevail where volatile stimuli are absent, weak or uninformative (Campbell & Borden, 2009). Favourable climatic conditions, frequently in combination with the late removal of infested timber, may lead to an outbreak of spruce bark beetles (Kautz et al, 2011a; Lausch et al, 2011). During such outbreaks, Ips typographus population density increases exponentially and emerging adults are able to infest and kill even healthy trees on a large scale, which changes Ips typographus into a primary pest (Reeve, 1997)

Objectives

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Conclusion