Risk of infestations by Dendroctonus mexicanus Hopkins and Dendroctonus frontalis Zimmermann bark beetles in forests of Michoacán

Introduction: Severe Dendroctonus spp. infestations are reported in North and Central America. Dendroctonus mexicanus Hopkins and Dendroctonus frontalis Zimmermann are recognized as forest pests and are common in the state of Michoacán, Mexico.Objective: To model current and future (2015-2039) spatial distribution of risk D. mexicanus and D. frontalis infestation in forests of Michoacán, Mexico.Materials and methods: Multicriteria evaluation techniques, including the analytic hierarchy process and fuzzy membership functions, were combined with climate and biophysical variables to obtain forest infestation risk maps for D. mexicanus and D. frontalis under current and future climate scenarios.Results and discussion: Climate, fire, tree density and topography were identified as relevant criteria influencing bark beetle outbreaks. The maximum risk value estimated for D. mexicanus was 0.78 and 0.83 for the current and future scenarios, respectively; for D. frontalis these values correspond to 0.84 and 0.85, respectively. In terms of area, high risk of infestation by D. mexicanus increased from 3.9 % (current scenario) to 5.0 % (future scenario); for D. frontalis it decreased from 10.8 % to 9.6 %. The very high-risk value remained constant (0.35 %) for both species and scenarios.Conclusions: Forests of the Transversal Volcanic Belt (in the northeastern part of Michoacán) have the highest risk of bark beetle infestation in the two modeled scenarios.

Weak spatial-genetic structure in a native invasive, the southern pine beetle (Dendroctonus frontalis), across the eastern United States

The southern pine beetle, Dendroctonus frontalis, is a native pest of pine trees that has recently expanded its range into the northeastern United States. Understanding its colonization, dispersal, and connectivity will be critical for mitigating negative economic and ecological impacts in the newly invaded areas. Characterization of spatial-genetic structure can contribute to this; however, previous studies have reached different conclusions about regional population genetic structure, with one study reporting a weak east-west pattern, and the most recent reporting an absence of structure. Here we systematically assessed several explanations for the absence of spatial-genetic structure. To do this, we developed nine new microsatellite markers and combined them with an existing 24-locus data matrix for the same individuals. We then reanalyzed this full dataset alongside datasets in which certain loci were omitted with the goal of creating more favorable signal to noise ratios. We also partitioned the data based on the sex of D. frontalis individuals, and then employed a broad suite of genotypic clustering and isolation-by-distance (IBD) analyses. We found that neither inadequate information content in the molecular marker set, nor unfavorable signal-to-noise ratio, nor insensitivity of the analytical approaches could explain the absence of structure. Regardless of dataset composition, there was little evidence for clusters (i.e., distinct geo-genetic groups) or clines (i.e., gradients of increasing allele frequency differences over larger geographic distances), with one exception: significant IBD was repeatedly detected using an individual-based measure of relatedness whenever datasets included males (but not for female-only datasets). This is strongly indicative of broad-scale female-biased dispersal, which has not previously been reported for D. frontalis, in part owing to logistical limitations of direct approaches (e.g., capture-mark-recapture). Weak spatial-genetic structure suggests long-distance connectivity and that gene flow is high, but additional research is needed to understand range expansion and outbreak dynamics in this species using alternate approaches.

Pinus elliottii (slash pine).

P. elliottii var. elliottii is an important timber species native to the lower coastal plain within the southeastern USA. Because of its rapid early growth and its production of highly valuable wood products, it has been widely introduced into other countries. As an exotic, it is used in Africa, especially in southern Africa, and in Australia and South America for various products ranging from lumber to pulpwood. In Brazil, it makes an important contribution to the resin production industry. The preferred method of regenerating P. elliottii is by clearcutting followed by chemical or mechanical site preparation, then direct seeding or planting of nursery stock. Although natural regeneration by seedtree, shelterwood, or group selection is an option, availability of genetically superior stock usually makes planting the favoured method of regeneration. Rotation lengths vary according to product objective. The optimum pulpwood rotation is about 25 years. In unthinned plantations, this age increases to 30 from 23 years as density increases and site index declines. South Florida slash pine (P. elliottii var. densa) is characterized by a grasslike, almost stemless stage, that lasts for 2 to 6 years. Variety densa has a small range, a less desirable tree form than var. elliottii, and is more difficult to regenerate. P. elliottii is particularly susceptible to fusiform rust (caused by Cronartium fusiforme) and is frequently attacked by the southern pine bark beetle (Dendroctonus frontalis). The best protection against insect attack is to maintain vigorous, healthy stands through good forest management. The wood is used for a wide variety of products. Markets and size and quality of the material determine whether it is used for sawlogs, veneer logs, poles, pilings, posts, pulpwood, particle board, or chip-n-saw logs. The straightness of the bole makes P. elliottii particularly suited for poles, pilings, and solid-wood products. Although it may often grow more slowly than P. patula and P. taeda, it can produce higher pulpwood yields due to its higher wood density. P. elliottii yields the best quality and highest quantity of commercial turpentine of all American pitch pines (Streets, 1962). However, this use has declined significantly as other sources of resins have become more readily available.

Revised and Potential New Tactics for the Suppression of Southern Pine Beetle Infestations

Cut-and-remove has been the recommended suppression technique for the suppression of infestations of the southern pine beetle (SPB), Dendroctonus frontalis Zimmermann (Coleoptera: Curculionidae), with cut-and-leave applied when conditions prevent removal of the felled pines. Changes in forest management practices and the timber industry, plus the expansion of SPB northward have led to an increased reliance on cut-and-leave in recent years. This change has resulted in an exploration of methods to improve the efficacy of cut-and-leave and the development of new tactics for suppressing SPB infestations. We describe these revised and new techniques and discuss their potential applications given current forest management conditions.

Semiochemicals for management of the southern pine beetle (Coleoptera: Curculionidae: Scolytinae): successes, failures, and obstacles to progress

The southern pine beetle, Dendroctonus frontalis Zimmermann (Coleoptera: Curculionidae: Scolytinae), is among the most destructive bark beetle pests of pines (Pinaceae) of the southeast and mid-Atlantic United States of America, Mexico, and Central America. Numerous volatile compounds can stimulate or reduce attraction of the beetle, but efforts to incorporate these into effective, practical technologies for pest management have yielded mixed results. Attractants have been incorporated into lures used in monitoring traps that are employed operationally to forecast outbreaks and detect emerging populations. The attraction inhibitor, verbenone, shows efficacy for suppressing southern pine beetle infestations but has not yet been adopted operationally. No effective semiochemical tree protectant has been developed for the beetle. We discuss complexities in the chemical ecology of the beetle that likely have impeded research and development of semiochemical management tools, and we describe basic science gaps that may hinder further progress if not addressed. We also report some supporting, original experimental data indicating (1) that a verbenone device can inhibit the beetle’s response to sources of attractant in a radius of at least several metres, (2) similar olfactory responses by the beetle to both enantiomers of verbenone, and (3) that pheromone background can cause conflicting results in semiochemical field tests.

INFLUENCIA DE LA SILVICULTURA EN LA INCIDENCIA DE DENDROCTONUS FRONTALIS, CAMPAMENTO, OLANCHO, MEDIANTE TECNOLOGÍAS DE INFORMACIÓN GEOGRÁFICA, 2000-2016

La presente la investigación se enmarco en desarrollar una respuesta científica a la problemática del gorgojo descortezador del pino, realizando una comparación entre los bosques de que han sido tratados bajo silvicultura versus los bosques que no han recibido ningún tratamiento silvicultural en el municipio de Campamento, Olancho, para determinar la influencia de la silvicultura en estos brotes de plaga de Dendroctonus frontalis. El objetivo general consistió en analizar las variaciones en la incidencia de la silvicultura el impacto de plaga de gorgojo descortezador del pino Dendroctonus frontalis, determinado mediante Tecnologías de la Información Geográfica en el municipio de Campamento, Olancho, en el periodo 2000-2016. Este análisis se realizó utilizando las herramientas tecnológicas como los Sistemas de Información Geográfica, para determinar si hay diferencias en los daños causados por el gorgojo descortezador del pino. Se utilizó herramientas de análisis espacial disponibles en los softwares especializados, se realizó mediante las metodologías y técnicas del análisis espacial de los datos geográficos. Se pudo concluir que existe una variación porcentual en la incidencia de la silvicultura de 19.86% en el área afectada por plaga bosque de pino y bosque mixto sin manejo forestal en el área de estudio equivalente a 466.52 hectáreas. Además, existe una variación porcentual en la incidencia de la silvicultura de 14.54% en el área afectada por plaga bosque de pino y bosque mixto con manejo forestal en el área de estudio equivalente a 1959.65 hectáreas.

Towards Sustainable Forest Management in Central America: Review of Southern Pine Beetle (Dendroctonus frontalis Zimmermann) Outbreaks, Their Causes, and Solutions

Outbreaks of the southern pine beetle (SPB) Dendroctonus frontalis Zimmermann in Central America have had a devastating impact on pine forests. It remains unclear to what extent these outbreaks are caused by the beetle’s ecology, climate, and historical management practices. Using research data and experience accumulated in northern latitudes to guide management of forests in Central America is associated with great uncertainty, given the many unique features of the conifer forests in this region. The main recommendation from this review is that Central American bark beetle outbreaks need to be studied locally, and the local climate, biotic elements, and silvicultural history need to be considered. The key to reducing the impacts of SPB in Central America are local research and implementation of proactive management, in order to facilitate the establishment of forests more resilient to increasing environmental and anthropogenic pressures.