http://www7.nau.edu/mpcer/direnet/publications/publications_f/files/Fettig_CJ_Klepzig_KD_Billings_RF_etal_The_Effectiveness.pdf

The effectiveness of vegetation management practices for prevention and control of bark beetle infestations in coniferous forests of the western and southern United States

https://digitalcommons.usu.edu/cgi/viewcontent.cgi?article=1018&context=barkbeetles

Resistance of conifers to bark beetle attack: Searching for general relationships

https://www.srs.fs.usda.gov/pubs/ja/1986/ja_1986_lorio_001.pdf

Growth-differentiation balance: A basis for understanding southern pine beetle-tree interactions

The nitrogen content of plant tissue is low relative to that of herbivores; as a consequence, dietary N can limit the growth and reproduction of herbivores and select for attributes that increase N acquisition. Bark beetles face a particularly severe challenge because the phloem that they consume is very low in nitrogen and phosphorus relative to their requirements. We quantified variation in the phloem concentrations of N and P in the host tree, Pinus taeda, and evaluated the following hypotheses regarding the role of sym- biotic fungi in nutrient budgets of the herbivore Dendroctonus frontalis: D. frontalis ex- perience variation in phloem nutrient concentrations across several spatial scales (HI); mycangial fungi enhance the diet of D. frontalis larvae by contributing to the acquisition of N and P (H2); Ophiostoma minus, an apparently antagonistic fungal symbiont, hinders D. frontalis larvae because it does not enhance nutrient concentrations of the phloem as much as mycangial fungi do (H3); and larvae of bark beetle species that lack mycangial fungi must consume more phloem to accomplish the same growth as larvae of D. frontalis (H4). In addition, we developed a general model for the N budgets of herbivorous insects that identifies the possible combinations of dietary and physiological parameters that can allow developmental success on low-nutrient diets. Spatial variation in phloem N was mostly at the level of trees within sites (a scale of meters) while P mostly varied among sites (a scale of kilometers). Trees with higher N content produced larger D. frontalis adults. Prior to infestation by beetles, phloem nutrient concentrations were very uniform within trees and very low relative to that of the bark beetles (N and P concentrations of D. frontalis adults were 28 and 8 times greater, re- spectively). During infestation, phloem nutrient concentrations increased overall and be- came highly variable within trees. Nitrogen concentrations increased from 0.40 + 0.01% (mean + 1 SE) in uninfested phloem to 0.86 + 0.03% in the phloem surrounding successfully developing D. frontalis larvae, which are typically associated with one or two species of mutualistic mycangial fungi. Nitrogen concentrations were intermediate in other micro- habitats within infested trees, including regions with no adult colonization, with failed larval development, or colonized by the antagonistic bluestain fungus 0. minus. We pa- rameterized a general nutrient-budget model for D. frontalis and a sympatric non-mycangial bark beetle, Ips grandicollis, which indicated that (1) mycangial fungi provide their benefits by concentrating dietary N for larvae; (2) 0. minus may exert its antagonistic effects on D. frontalis larvae by failing to concentrate dietary N as much as mycangial fungi do; (3) non-mycangial bark beetles meet their N budgets through high consumption of unaltered, low-N phloem; and (4) larvae should easily meet their P requirements with any combination of consumption rate and development time that allows them to meet their N requirements. Alternative strategies for N acquisition may have general consequences for the population dynamics and community interactions of bark beetles.

/pdf/nitrogen-budgets-of-phloem-feeding-bark-beetles-with-and-1ji6x3096m.pdf

Nitrogen budgets of phloem-feeding bark beetles with and without symbiotic fungi

One expected effect of global climate change on insect populations is a shift in geographical distributions toward higher latitudes and higher elevations. South- ern 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 incor- porated 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 under- lying long-term distributional shifts of their host forests.

https://www.nrs.fs.fed.us/pubs/jrnl/2002/ne_2002_williams-d_001.pdf

Climate change and the outbreak ranges of two North American bark beetles

The Southern pine beetle, Dendroctonus frontalis Zimmerman (Coleoptera: Scolytidae), is the most destructive insect pest of pine forests in the southeastern United States and in parts of Mexico and Central America (Fig. 1). This is a well-worn statement but is nonetheless richly deserved and quite accurate. The beetle epitomizes the definition of its genus, killer of trees. As such, D. frontalis can overcome even vigorous trees when its populations are large. In the United States, the southern pine beetle primarily colonizes loblolly (Pinus taeda) and shortleaf (P. enchinata) pines, both of which are important sources of pulp and timber. These pines are fast-growing species, inhabiting some of the finest timber-growing land on the continent. In addition, most watersheds in the southern pine forest are dominated by these species, and in many recreational areas high-valued old growth pine prevail.

The Southern Pine Beetle

Population dynamics of the southern pine beetle Dendroctonus frontalis has been the subject of intensive research in the USA for more than a decade. TAMBEETLE, an acronym for the mechanistic model of population dynamics of D. frontalis, was developed to abstract contemporary knowledge on the insect. This model was developed as a joint venture between the Biosystems Research Group of Industrial Engineering and the Department of Entomology at Texas A&M University. The approach used to develop the model and the structure of component submodels is described. Research leading to the development of the model involved a series of field and laboratory studies aimed at various aspects of the population system of the insect. This research is reviewed. Important areas needing further research are identified. Studies dealing with factors involved in initiation of infestions, biome-level epidemiology, host susceptibility, stand modeling, and dynamics of within-tree mortality were emphasized as important topics for further research.

An overview of the TAMBEETLE model of Dendroctonus frontalis population dynamics

An inhibitor-based tactic can suppress southern pine beetle, Dendroctonus frontalis Zimmermann, infestations using the anti-aggregation pheromone, verbenone. However, it is unknown whether southern pine beetle and its insect natural enemies are impacted by this tactic. We evaluated potential effects by examining mean trap catches, aggregation measures, species diversity and abundance indices, and interspecific covariation between southern pine beetle and its most common insect enemies. Examination of flight and landing trap catches, before and after application of verbenone to infestations, showed that southern pine beetle and its natural enemies remained at the sites at similar densities, continued their associations, and maintained similar spatial distributions. This suggests that verbenone reduces successful colonization of unattacked trees and has no negative effect on the relationship of southern pine beetle with its natural enemies.

Effect of an Inhibitor-Based Suppression Tactic on Abundance and Distribution of the Southern Pine Beetle (Coleoptera: Scolytidae) and Its Natural Enemies

Use of the Dendroctonus frontalis inhibitor pheromone verbenone, as a treatment on trees within infestations, is effective in suppressing or halting infestation growth. It is hypothesized that the inhibitor disrupts the orientation of flying adult D. frontalis to host trees and, as a result, sufficient attacking adults are not available at any given time on a tree to successfully over take it. Seasonal changes in abundance, longevity, and dispersal of beetle populations may impact the effectiveness of the inhibitor-based treatment.

Disruption of Dendroctonus frontalis (Col., Scolytidae) infestations with an inhibitor

Bark/phloem disk sandwiches (100 cm2) were colonized with one to six mating pairs of the southern pine beetle, Dendroctonus frontalis Zimm., to observe gallery construction and evaluate if avoidance behavior occurs between beetles. Frequencies of turn aways, touches, and crosses (three characteristics used to describe conspecific interaction) all increased significantly with beetle density. A threshold of three mating pairs within the 100- cm2 phloem area was the density at which avoidance behavior became evident. At a threshold of five mating pairs the number of gallery crossings was significantly greater than at lower densities. Single and paired female beetles introduced into artificial galleries crossed empty neighboring galleries significantly more often than when neighboring galleries were occupied with other D. frontalis. The data suggest that D. frontalis females can regulate gallery spacing within the host through their ability to detect nearby beetles and their galleries. Possible spacing mechanisms are discussed.

Thomas L. Payne

Papers

The Southern Pine Beetle

An overview of the TAMBEETLE model of Dendroctonus frontalis population dynamics

Effect of an Inhibitor-Based Suppression Tactic on Abundance and Distribution of the Southern Pine Beetle (Coleoptera: Scolytidae) and Its Natural Enemies

Disruption of Dendroctonus frontalis (Col., Scolytidae) infestations with an inhibitor

Laboratory study of conspecific avoidance by host-colonizingDendroctonus frontalis Zimm. (Coleoptera: Scolytidae)