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Goal: Apply Knowledge Globally How do insects, diseases, and weather disturbances interact? An assessment of current knowledge for the South

Director’s Choice
A fallen tree in a forest after an ice storm
Ice storms are a regular disturbance in Southern forests. Like wind storms, they can cause varying levels of damage. Snapped, leaning, and downed trees can be easily observed, while standing but stressed or injured trees may not be as apparent. (Forest Service photo by Don Bragg)

Introduction

Forests in the northern and western U.S. and Europe have been well-studied in terms of wind disturbance and subsequent insect infestations, but those relationships are not as clear in the southern U.S. SRS researchers synthesized the state-of-the-knowledge around weather disturbances and their interactions with forest pests and pathogens in the South. While some phloem-feeding bark beetles increase in dead and dying trees following disturbance, there are no published data supporting anecdotal reports that southern pine beetle may reach outbreak status as a result of weather disturbances.

Summary

Forests in the southern U.S. experience a wide variety of weather-related disturbances, from fine-scale events with management implications for one or a few landowners to major hurricanes that impact many ownerships across multiple states. The immediate impacts of catastrophic weather disturbance are obvious—trees are killed, stressed, or damaged due to wind, flooding, ice, hail, or some combination of events. How forests respond to disturbance depends on several factors, including forest types and attributes, ecoregion, local pressure from invasive plants, preexisting infestations of pests and pathogens, prior disturbance events, and other variables which interact in complex ways, influencing successional dynamics and management decisions.

Researchers synthesized the major weather perturbations affecting the forests of the southern U.S. and current state of the knowledge surrounding interactions between these events, forest pests, and forest diseases in a new publication. The research compiles non-quantitative observations between 1955 and 2018 from annual USDA Forest Service “Major Forest Insect and Disease Conditions in the United States” reports that describe where insects or diseases were found on trees that were stressed by weather disturbances.

The research presents two conceptual models, one describing changes in forest structure and composition and another that outlines herbivorous pest population fluctuations following different severity levels of disturbance. Finally, the study proposes eleven questions that require additional research to better inform sustainable forest management decisions in preparation for and in response to catastrophic weather events.

Principal Investigators
James T. Vogt, Project Leader / Supervisory Biological Scientist
Don Bragg, Project Leader
Rabiu Olatinwo, Research Plant Pathologist
RWUs
4552 - Insects, Diseases, and Invasive Plants
4159 - Southern Pine Ecology and Management
Strategic Program Area
Inventory and Monitoring
Publication
Interactions between weather-related disturbance and forest insects and diseases in the Southern United States
External Partners
Kamal Gandhi - University of Georgia, Warnell School of Forestry & Natural Resources
Kier Klepzig - The Jones Center at Ichauway