Richard O. Flamm

Disturbance propagation by bark beetles as an episodic landscape phenomenon

Landscapes are the resultant of ecological processes and events operating on many different space-time scales. Large scale disturbance is recognized as a major influence on landscape patterns, but the impact of small scale events is often overlooked. We develop an hierarchical framework to relate lightning and bark beetle population dynamics to the southern pine forest landscape using the concepts of disturbance propagation and amplification. The low level lightning disturbance can be propagated to the landscape level when weather and forest stand structure facilitate bark beetle epidemics. We identify epidemics as biotically-driven episodes that alter landscape structure. The concept of the landscape as the spatial dimension of these episodes is represented in a conceptual model linking insect-host and landscape mosaic interactions.

The Southern Pine Beetle

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 Integrated Southern Pine Beetle Expert System: ISPBEX☆

Abstract The Integrated Southern Pine Beetle Expert System (ISPBEX) was developed to address the fundamental issue of pest management: how to use existing and forthcoming information for the purposes of problem solving and decision making. In this article, we define the problem of southern pine beetle management, recount the history of ISPBEX development, examine the structure and function of the implemented version of ISPBEX, and describe the knowledge system environment approach that is being used in development of the next version of the system. ISPBEX is a task-oriented knowledge-based system. It considers three aspects of integrated pest management : suppression, prevention, and utilization. These subject areas are represented as modules in ISPBEX. Each module contains specific advisors. Major emphasis has been placed on the suppression module which consists of five advisors that deal with treatments, presuppression economic evaluation, postsuppression economic evaluation, infestation forecasting, and project budgeting. The treatment advisor was Beta tested during 1989. A new version of ISPBEX is currently under development. It is an implementation of the Knowledge System Environment (KSE) concept. This new system will provide for knowledge-based interpretation of each of the different types of information and will include a facility for analysis and display of spatially referenced data.

Estimatingdendroctonus frontalis (Coleoptera: Scolytidae) daily infestation dynamics

Mathematical procedures are given to estimate infestation totals and daily life stage arrivals, departures, and mortality ofDendroctonus frontalis Zimmermann for an infested tree in the field. These estimates are based on minimal sample data and are designed to utilize all available information. Daily arrival estimates for larvae, pupae, and callow adults are obtained by indirect analysis without direct observation of these stages. The procedures are applied to 147 infested trees, and the results are transformed to a common time basis to obtain daily expectations by life stage for an “average” tree. These expectations suggest optimal times for field sampling or relative times of sampling when optimal times are missed. Expected daily arrival distributions by life stage for a single egg and a single attacking adult are given. Procedures are given for utilizing collateral information to obtain an infestation total and daily arrival estimates for a boundary life stage. The results of this study are applicable to anyD. frontalis field study, and the procedures given are applicable to any bark inhabiting insect having similar habits.

Traumatized Hosts: Their Influence on the Population Dynamics of the Southern Pine Bark Beetle Guild

There is considerable interest worldwide in understanding the interactions between plants and insects. Typically, studies focus on the interactions of individual plants and insects and then extrapolate to the population level. This extrapolation may be misleading because studies at the level of the individual necessarily simplify and overlook many abiotic and biotic factors of the environment which affect population-level performance. Therefore, population-level predictions formed from studies at the individual level may differ substantially from actual observations made at the population level. In this chapter, we study host/insect interactions directly at the population level. We compare parameters of bark beetle population dynamics in traumatized trees (host defenses presumed to be largely removed) and in naturally infested pines (defenses presumed to be relatively intact) to examine the role of disturbed trees in the epidemiology of the southern pine bark beetle guild. Specifically, we consider (1) arrival densities, (2) attack densities, (3) colonization distributions, (4) emergence densities, (5) oviposition, (6) brood production, and (7) survivorship of bark beetles.