- 1 After storm disturbances, there is a risk for degradation of the quality of fallen trees, and for subsequent tree mortality caused by the spruce bark beetle Ips typographus (L.) (Coleoptera: Curculionidae). Models assessing the risk for bark beetle colonization of different kinds of storm gaps would be a valuable tool for management decisions.
- 2 The present study aimed to determine which gap and landscape characteristics are correlated with the probability of colonization of wind‐felled Norway spruce trees by I. typographus.
- 3 The study included 36 storm gaps, varying in size from three to 1168 wind‐felled spruces, created by the storm Gudrun in southern Sweden in January 2005.
- 4 In the first summer, on average, 5% of the wind‐felled spruces were colonized by I. typographus. The percentage of colonized wind‐felled trees per gap was negatively correlated with the total area of storm gaps within 2000 m in the surrounding forest landscape.
- 5 In the second summer, the proportion of colonized trees increased to 50%. Both gap (mean diameter of wind‐felled trees and basal area of living spruce trees) and landscape variables (amount of spruce forest) were significantly correlated with colonization percentage and explained almost 50% of the variation between gaps.
- 6 There was no relationship between gap area and colonization percentage. This implies that landscapes with many large storm gaps, where logging resources will be most effectively used, should be salvaged first.
- 1 DISRUPT Micro‐Flake Verbenone Bark Beetle Anti‐Aggregant flakes (Hercon Environmental, Inc., Emigsville, Pennsylvania) were applied in two large‐scale tests to assess their efficacy for protecting whitebark pine Pinus albicaulis Engelm. from attack by mountain pine beetle Dendroctonus ponderosae Hopkins (Coleoptera: Scolytinae) (MPB). At two locations, five plots of equivalent size and stand structure served as untreated controls. All plots had early‐ to mid‐outbreak beetle populations (i.e. 7.1–29.2 attacked trees/ha). Verbenone was applied at 370 g/ha in both studies. Intercept traps baited with MPB aggregation pheromone were placed near the corners of each plot after the treatment in order to monitor beetle flight within the plots. Trap catches were collected at 7‐ to 14‐day intervals, and assessments were made at the end of the season of stand structure, stand composition and MPB attack rate for the current and previous years.
- 2 Applications of verbenone flakes significantly reduced the numbers of beetles trapped in treated plots compared with controls at both sites by approximately 50% at the first collection date.
- 3 The applications also significantly reduced the proportion of trees attacked in both Wyoming and Washington using the proportion of trees attacked the previous year as a covariate in the model for analysis of current year attack rates; in both sites, the reduction was ≥ 50%.
- 4 The flake formulation of verbenone appears to have promise for area‐wide treatment by aerial application when aiming to control the mountain pine beetle in whitebark pine forests.
- 1 One expected effect of global climate change on insect populations is a shift in geographical distributions toward higher latitudes and higher elevations. Southern pine beetle Dendroctonus frontalis and mountain pine beetle Dendroctonus ponderosae undergo regional outbreaks that result in large‐scale disturbances to pine forests in the south‐eastern and western United States, respectively.
- 2 Our objective was to investigate potential range shifts under climate change of outbreak areas for both bark beetle species and the areas of occurrence of the forest types susceptible to them.
- 3 To project range changes, we used discriminant function models that incorporated climatic variables. Models to project bark beetle ranges employed changed forest distributions as well as changes in climatic variables.
- 4 Projected outbreak areas for southern pine beetle increased with higher temperatures and generally shifted northward, as did the distributions of the southern pine forests.
- 5 Projected outbreak areas for mountain pine beetle decreased with increasing temperature and shifted toward higher elevation. That trend was mirrored in the projected distributions of pine forests in the region of the western U.S. encompassed by the study.
- 6 Projected outbreak areas for the two bark beetle species and the area of occurrence of western pine forests increased with more precipitation and decreased with less precipitation, whereas the area of occurrence of southern pine forests decreased slightly with increasing precipitation.
- 7 Predicted shifts of outbreak ranges for both bark beetle species followed general expectations for the effects of global climate change and reflected the underlying long‐term distributional shifts of their host forests.
- 1 Bark beetles are significant mortality agents of conifers. Four beetle species, the pine engraver Ips pini, the six‐spined pine engraver Ips calligraphus sub. ponderosae, the southern pine beetle Dendroctonus frontalis, and the western pine beetle Dendroctonus brevicomis, cohabitate pines in Arizona.
- 2 A pheromone trapping study in ponderosa forests of Arizona determined the attraction of beetles to conspecific and heterospecific pheromone components in the presence and absence of host volatiles, and tested whether predators differ in their attraction to combinations of pheromone components and tree monoterpenes.
- 3 All four bark beetle species differed in their responses to heterospecific lures and monoterpenes. Ips calligraphus was the only species that increased in trap catches when heterospecific lures were added. Heterospecific lures did not inhibit the attraction of either Dendroctonus or Ips species. The replacement of myrcene with α‐pinene increased the attraction of Dendroctonus, whereas the addition of α‐pinene had mixed results for Ips. The prominent predators Temnochila chlorodia and Enoclerus lecontei were more attracted to the I. pini lure than the D. brevicomis lure, and the combination of the two lures with α‐pinene was most attractive to both predator species.
- 4 Cross attraction and limited inhibition of bark beetles to heterospecific pheromones suggest that some of these species might use heterospecific compounds to increase successful location and colonization of trees. Predator responses to treatments suggest that tree volatiles are used to locate potential prey and predators are more responsive to Ips than to Dendroctonus pheromone components in Arizona.
- 1 Adult Ips typographus were collected using pheromone traps at a locality in the eastern part of Austria between 1995 and 2004. The occurrence of two pathogens, Gregarina typographi and Chytridiopsis typographi, was determined throughout the period of beetle swarming activities. Weekly and annual data sets were then analysed by smoothing statistical techniques and epidemiological models.
- 2 The pathogens spread differently within the beetle population with respect to their biological characteristics: infectious forms of C. typographi were immediately available after their development in the insect's gut, but not those of G. typographi.
- 3 Both of the pathogens had a low prevalence in swarming beetles, especially C. typographi, and there was no evidence of a between‐year or within‐year epidemiological process. Conversely, it was shown that G. typographi has a positive effect on the rate of increase of trapped beetles.
- 4 Fitting a nonlinear model to the data suggested that: (i) this was due to a higher catch ability of beetles infected with G. typographi than of healthy beetles; (ii) when this effect is taken into account, G. typographi induces a specific within‐year low mortality in beetle populations; and (iii) beetle populations increase naturally within a year, despite their infection by both pathogens. No clear effect of C. typographi was detected in the trapped data set when the prevalence of this species was high in beetle populations collected from trees.
- 5 It is hypothesized that both pathogens induce different behavioural effects on their host, resulting in: (i) favouring the trapping of G. typographi‐infected beetles and (ii) hindering the capture of C. typographi‐infected individuals. This could be the result of both of the pathogens having an opposite effect on the flight abilities of beetles and/or on the beetles' response to the aggregation pheromones used in the traps.
The small spruce bark beetle Ips amitinus is a widespread species in many European countries that has been actively spreading into Northern Europe in the recent decades. In Russia, I. amitinus is present in the western, northwestern, and northern regions of the European part, with a tendency for range expansion. The species was first recognized in West Siberia in 2019 by characteristic morphological features and molecular genetic analysis. This bark beetle is abundant on Pinus sibirica in Siberian pine forests located near settlements within Tomsk and Kemerovo provinces, and is also sporadically found on the Siberian spruce Picea obovata. It colonizes the upper trunk and branches of standing and windfall trees. In the outbreak foci this bark beetle causes catastrophic drying of Siberian pines, starting from the crown top. This pattern of tree drying was noted for the first time near settlements in Yashkinsky District of Kemerovo Province in 2014, and now outbreak foci of I. amitinus exist in all the Siberian pine forests in this district. The population growth of I. amitinus was probably facilitated by dry and hot summer weather in the southeast of West Siberia during the last decade, in 2011 and 2012, and also by heavy winter snowfalls leaving numerous snapped tree branches which are easily colonized by the pest. In Tomsk Province, the most active outbreak focus of I. amitinus appeared in 2018 in the Siberian pine forest near Luchanovo and Ipatovo, following an outbreak of the Siberian moth Dendrolimus sibiricus. The invasion of I. amitinus in Siberia may increase the degradation rates not only of the gene-reserve Siberian pine forests but also of other dark coniferous stands.
相似文献- 1 Endemic populations of the bark beetle Dendroctonus ponderosae attack weakened lodgepole pine (Pinus contorta var. latifolia) trees that are often previously infested by other bark beetle species, such as Pseudips mexicanus.
- 2 The effect of interactions on D. ponderosae was assessed by examining host selection and productivity of D. ponderosae in trees containing P. mexicanus and trees infested solely by D. ponderosae.
- 3 The findings obtained show that D. ponderosae attacked hosts previously occupied by P. mexicanus at greater densities, and offspring emerged earlier compared with hosts infested by D. ponderosae alone. Additionally, D. ponderosae larvae in P. mexicanus‐infested trees were found to require a significantly lower amount of resource to complete development with no loss in size.
- 4 The presence of P. mexicanus may affect host condition, improving the subcortical environment for endemic D. ponderosae, ultimately aiding in population maintenance at low levels. Hosts in this state should be preferentially attacked by D. ponderosae.