Anne Franklin

Post-storm surveys reveal large-scale spatial patterns and influences of site factors, forest structure and diversity in endemic bark-beetle populations

The storm that struck France on december 26th and 28th 1999 felled 140 million m3 of timber and had a high economic, social and landscape impact. This event offered the opportunity to study large-scale patterns in populations of forest insect pests that would benefit from the abundant breeding material. A large-scale survey was carried out in France in 2000 to sample the most frequently observed species developing on spruce (Ips typographus, Pityogene schalcographus) and pine (Tomicus piniperda, Ips sexdentatus) in 898 locations distributed throughout wind-damaged areas. The local abundance of each species scored on a 0 to 5 scale was analysed using geostatistical estimators to explore the extent and intensity of spatial autocorrelation, and was related to site, stand, and neighbourhood landscape metrics of the forest cover (in particular the interconnection with broadleaf forest patches) found within dispersal distance. All species but I. sexdentatus, which was much less abundant, displayed large-scale spatial dependence and regional variations in abundance. Lower infestation levels per tree (windfalls and standing trees) were observed in stands with a high proportion of wind-damaged trees, which was interpreted as the result of beetles distributing themselves among the available breeding material. More infestations were observed in wind-broken trees as compared to wind-felled trees. More importantly, populations showed significant relationships with the structure of coniferous stands (in particular with the number of coniferous patches). T. piniperda population levels were negatively correlated to the amount of coniferous edge shared with broadleaf forest patches, possibly because of the disruptive effect of non-host volatiles on host-finding processes at the landscape-scale. The differences observed between species regarding patterns and relationships to site, stand, and forest cover characteristics are discussed in relation to the ecological characteristics of each species.

Recapture of Ips typographus L. (Col., Scolytidae) with attractants of low release rates: localized dispersion and environmental influences.

1 The dispersal of Ips typographus L. (Col., Scolytidae) was studied using a mark–release–recapture approach in a grid of traps equipped with pheromone lures of release rates of about 8.4 mg/day of 2‐methyl‐3‐buten‐2‐ol (MB) and 0.29 mg/day of (S)‐cis‐verbenol (cV) in experiment 1, and 1.2 mg/day of MB and 0.04 mg/day of cV in experiment 2.

Occurrence of Ips typographus (Col., Scolytidae) along an urbanization gradient in Brussels, Belgium

Abstract  1 The distribution and dynamics of insect populations in cities is poorly understood. One approach to address this question is to explore the permeability of the urban habitat to species from surrounding rural areas, which can serve as reservoirs in source‐sink dynamics.

Dose-dependent response and preliminary observations on attraction range of Ips typographus to pheromones at low release rates

Responses of the European spruce bark beetle, I. typographus (Coleoptera: Scolytidae), to low release-rate pheromones were investigated in two experiments in a spruce forest at Wellin, southern Belgium. Dose–response of the beetle was first examined in a trapping experiment in August 1999. The major pheromone components of I. typographus, (S)-cis-verbenol (cV) and 2-methyl-3-buten-2-ol (MB) were released from window traps. Five treatments were replicated five times: (1) blank trap, (2) 0.03 and 1.2, (3) 0.11 and 4.5, (4) 0.34 and 15.2 mg/day of cV and MB, respectively, and (5) Pheroprax. Trap catches increased linearly as a function of increasing release rates of cV and MB. A second study aimed at making preliminary observations on the attraction range of the pheromones as compared to Pheroprax. A release–recapture experiment was carried out in May 2000: four trap-trees located 50 m away from a central release platform were equipped with window traps baited with increasing release rates, tested in separate releases: 0.03 and 1.2; 0.11 and 4.5; 0.34 and 15.2 mg/day of cV and MB, respectively, and Pheroprax. Recaptures increased with the release rate. Trap catches were different at lower release rates, but not between the release rate of 15.2 mg/day of MB and Pheroprax. Variations in captures in relation to wind parameters showed persistently random flight at the lower release rates. Significant upwind flight was observed for Pheroprax only. These results imply that trap interference existed for Pheroprax and suggest that its attraction range may be greater than 50 m.

Canopy herbivore community structure: large-scale geographical variation and relation to forest composition

Abstract.  1. Geographical distributions of individual foliage‐feeding forest herbivore species have been found to be aligned closely with the distribution of their host trees, however little is known about the extent to which broad herbivore communities are geographically associated with distinct host communities.

Occurrence of Ips typographus (Col., Scolytidae) along an urbanization gradient in Brussels, Belgium: Occurrence of I. typographus along an urbanization gradient

Abstract  1 The distribution and dynamics of insect populations in cities is poorly understood. One approach to address this question is to explore the permeability of the urban habitat to species from surrounding rural areas, which can serve as reservoirs in source‐sink dynamics.