The frightful four: the top forest health threats in the South today

Aerial image showing pine mortality, some green trees some dead brown trees

Southern forests across the United States are encountering some significant challenges right now. These forests, known for their beauty, ecological significance and substantial economic impact, are facing various environmental and biological threats in 2024. From towering pines to sprawling oaks, our trees are facing issues that need attention and decisive action.

A key factor in addressing these challenges is the strong partnership between southern state forestry agencies, the USDA Forest Service and other key partners. Together, these collaborations are critical in implementing effective strategies and solutions. In this blog, we will explore the top four southern forest health threats of 2024, highlighting the critical issues and proactive measures being taken by our partners to combat them.

1. Drought/Ips bark beetles

In the late summer and fall of 2023, a “hot drought,” which is characterized by little to no precipitation combined with maximum temperatures 5-10 degrees above normal, impacted Mississippi and Louisiana. Across these states, pine trees began dying in response to outbreaks of Ips bark beetles during the late fall and winter months of 2023 and into 2024. Ips bark beetles are less aggressive than the more well-known southern pine beetle, but they can become a serious problem when pines are vulnerable to pests during periods of sustained environmental stress.

As a result, an estimated 150,000 acres of pine mortality occurred across these two states, although some of the mortality, about 20,000 acres, was attributed to wildfire. Most of the tree mortality that was accounted for was loblolly pine in plantation or mixed forest settings, but there were also huge economic impacts to urban forest landscapes, which remain under-documented. This includes impacts to street and yard trees, woodlots, parks, cemeteries, golf courses and transportation/powerline rights-of-way areas.

What We’re Doing:

Region 8 Forest Health Protection collaborated with the Eastern Forest Environmental Threat Assessment Center (EFETAC), a branch of Forest Service Research, to assess the scope of the damage using satellite imagery analysis. This analysis allowed us to produce a very spatially accurate pine mortality map within a matter of weeks. Normally, such an assessment would have taken months of difficult and sometimes dangerous aerial and ground survey work by many people for a disturbance of this scale and magnitude. Furthermore, the spatial accuracy obtained with satellite imagery would have been impossible using traditional survey approaches.

Pine Mortality map example — *Mississippi Pine Mortality Map. Credit: Mississippi Forestry Commission*

Having a spatially accurate pine mortality map and an estimate of the scope of the damage helped provide essential information to the Mississippi Forestry Commission and Louisiana Department of Agriculture and Forestry so that they could begin the process of receiving financial assistance for their many impacted landowners. The USDA Forest Service is currently working with the Farm Service Agency to provide reforestation support to impacted landowners through the Emergency Forest Restoration Program (EFRP). In addition, this event led to a proposed bill to amend the Agricultural Credit Act of 1978 to authorize assistance for emergency measures in response to pine beetle outbreaks. If passed, this would be the first federal legislation that directly addresses impacts to forests from bark beetle outbreaks.

Contributed by Chris Asaro, USFS Region 8

2. Southern Pine Beetle

Southern Pine Beetle in flight — *Credit: Alabama Forestry Commission*

Southern Pine Beetle (SPB) is a native bark beetle in the South. Most landowners and forest managers are familiar with SPB because it can have a tremendous impact on southern yellow pine during outbreak. While we have seen several regionally significant outbreaks and impacts over the years, based on observed activity in autumn 2023 and results from the annual spring trapping survey conducted by state forestry agencies and the USDA Forest Service, there is a high likelihood that SPB activity could be significant this year. Several states could have moderate to high activity in 2024 – particularly Alabama, Georgia, Mississippi and South Carolina.

What We’re Doing:

The USDA Forest Service and the Southern Group of State Foresters have been conducting the Southern Pine Beetle Prevention Program for the past 20 years. More than 1.4 million acres have been treated, mostly through state-administered cost-share programs (with approximately 18,000 landowners participating). Treatments include thinning and prescribed fire to maintain open forest conditions and restoring less susceptible pine forests.

southern pine beetle trap hanging in a forest — *This year, state agency forest health specialists have so far installed 506 traps across the 13 southeastern states. Credit: Alabama Forestry Commission.*

Additionally, the USDA Forest Service provides funding and technical expertise to its own National Forests to prevent and suppress SPB infestation. This in turn helps mitigate further spread to surrounding areas, including private forest lands which account for 87% of all forested areas in the South. Contact your state forest health specialist for more information about the SPB Prevention Program, or if you suspect that you have SPB present on your land.

Contributed by John Nowak, USFS Region 8

SPB Outbreak Prediction Tool

3. Spongy Moth

*Newly hatched spongy moth caterpillars feeding on white oak on the George Washington National Forest. Credit: U.S. Forest Service*

Spongy moth, an exotic species formerly known as gypsy moth, commonly reaches outbreak numbers every eight to twelve years in the United States. Spongy moth caterpillars can feed on hundreds of species of trees and shrubs, but particularly target oak trees. When caterpillars repeatedly eat all the leaves on trees during outbreaks, trees can die. In 2023, spongy moth outbreaks impacted 1.3 million acres in 13 states across the Midwestern and Eastern U.S.

In northern Virginia, spongy moth outbreaks have been impacting the area since 2022. The outbreak has already killed mature trees across all land ownerships. Because of the high population densities, caterpillars can also be a nuisance to homeowners and forest-goers as they move between trees. Furthermore, the long hairs on the caterpillars can cause allergic reactions to some people.

What We’re Doing:

Following the 2024 summer season, surveys will assess the impact of the current outbreak and the potential for additional injury in 2025. The USDA Forest Service partners with numerous state agencies and the USDA Animal and Plant Health Inspection Service to implement the USDA Spongy Moth Management Program. This program utilizes four strategies to reduce the impact and spread of this exotic species across the U.S.

Helicopter conducting aerial applications of spongy moth using Btk, an insect bacterium. — *Aerial applications of spongy moth using Btk, an insect bacterium. Credit: U.S. Forest Service*

For example, the USDA Forest Service’s Region 8 Forest Health Protection office collaborated with the George Washington National Forest and Shenandoah National Park to preserve high-value forests located within the outbreak. Forests were treated with aerial applications in mid-May to save campgrounds, trailheads and other high-use areas. An insect bacterium, known commonly as Btk, that specifically kills feeding caterpillars was used to suppress the high-population densities. State Parks and private landowners also conducted aerial applications because the outbreaks were so widespread. Recent activities of the USDA Spongy Moth Management Program include the Slow the Spread Program.

Contributed by Tom Coleman, USFS Region 8

State Feature

Virginia DOF employee holds a leaf with a spongy moth caterpillar

Brown mountainsides due to spongy moth feeding caught the attention of many Virginia landowners this spring.

Brown mountainsides due to spongy moth feeding caught the attention of many Virginia landowners this spring, and Virginia Department of Forestry (VDOF) staff were available to respond to questions and concerns. Spongy moth damage in Virginia has been documented since the 1980s, most often in western Virginia along ridgetops where oak trees are common. VDOF Forest Health program staff conducted ground and aerial surveys to map spongy moth damage this spring. In total, over 85,000 acres with damage were mapped in the Shenandoah Valley. Devil’s Backbone Virginia State Forest, which lies in the middle of the infested area, was treated in May with an aerial application of biopesticide. In addition, evidence of biological control agents (an Entomophaga fungus and a nucleopolyhedrosis virus) have been found causing spongy moth caterpillar mortality. While some Virginia forestland will sustain long-term impacts from this spongy moth outbreak, suppression treatments and biological control could lead to a reduction in spongy moth populations next year.
Contributed by Lori Chamberlin, VDOF

4. Brown Spot Needle Blight

Longleaf pine seedling with advanced symptoms of brown spot needle blight. Photo by George Blakeslee, University of Florida.

Brown spot needle blight (BSNB) is emerging needle disease on loblolly pines in the southeastern states. The fungal pathogen, Lecanosticta acicola, has been known to cause severe damage on longleaf pines at grass stage, but is now becoming a serious threat to health of loblolly pines since 2016. BSNB on loblolly pines has been confirmed in 115 counties from nine states (AL, AR, FL, GA, LA, MS, SC, TN, and TX) while most severe cases were reported from AL, AR, LA, and MS with landscape scale damages on mature trees and/or localized damages on younger trees in commercial stands. Mortality and growth loss have been observed from the younger trees after repeated infections over multiple growing seasons. Infestations of Ips bark beetles also have been observed on the trees weakened by BSNB.

What We’re Doing:

The U.S. Forest Service is managing a county-level map to monitor distribution and occurrence of BSNB on loblolly pines. Since the disease is an emerging issue on loblolly pines, many aspects of this pathosystem are unknown, including population genetics of the pathogen, tree families resistant to BSNB and interaction of environmental conditions. Field observations suggest that certain tree families are less susceptible to BSNB, and Forest Service-FHP Resistance Screening Center in cooperation with University of Georgia is testing loblolly seedlings with different genetic background to identify resistant families. Researchers from universities, tree cooperative programs and the U.S. Forest Service in the southeastern states are investigating population genetics, risk model, remote sensing, long-term monitoring, silvicultural practices and data portal development that will provide critical information for BSNB management. Most of these studies are conducted through a regional pine needle pathogens research network funded by the USDA Forest Service.

Contributed by Jaesoon Hwang, USFS Region 8 & Rabiu Olatinwo, USFS-SRS

Southern forests are at a crossroads. The combined impact of drought, pest outbreaks and invasive species poses a serious threat to their health and sustainability. However, through the concerted efforts of federal and state agencies, key partners and private landowners, combined with innovative technologies and active forest management practices, there is hope for mitigating these threats. By staying informed and proactive, we can ensure that southern forests continue to thrive for generations to come.