The health of our forests: 2019 year-in-review

by | Jan 1, 2020

North Carolina is home to beautiful forests which encounter risks from various threats each year.  The significance of native pests vary by year, but the threat from invasive pests is only increasing with time. The N.C. Forest Service (NCFS) Forest Health Branch aims to protect our forests from native and invasive insects alike by monitoring their movement and populations, implementing management, and promoting practices that reduce further harm. Enjoy this quick overview of the worst pests in our state this year.

Emerald Ash Borer

In 2019, the emerald ash borer was detected in 18 additional counties within the state: Alleghany, Ashe, Burke, Caldwell, Chatham, Cherokee, Davie, Henderson, Lenoir, McDowell, Nash, Polk, Rowan, Rutherford, Stokes, Watauga, Wilkes, and Yadkin. This brings the total number of affected counties to 55 since its initial detection in N.C. in 2013.

The emerald ash borer was detected in 18 new counties in 2019. Image: Kelly Oten, N.C. Forest Service.

The Ash Protection Program, launched last year, is a program that provides financial support to communities wishing to protect their urban ash trees with pesticides. This year, nine communities protected over 400 trees through this program.

While pesticides are a viable option in urban and landscape settings, it is not typically viable in forest settings. Through cooperative efforts with the United States Department of Agriculture, Animal and Plant Health Inspection Service (USDA-APHIS), the NCFS participates in a long-term management effort by releasing biocontrol agents at sites in Chatham, Granville, Forsyth, Vance, Wake, and Wayne Counties.

Hemlock Woolly Adelgid

The hemlock woolly adelgid (HWA) was first detected in N.C. in 1995 and has since spread to all regions where hemlocks naturally occur in the state.  Hemlocks continue to suffer at an alarming rate from these infestations.

Four years ago, a cooperative effort between the NCDA&CS, WNC Communities, U.S. Forest Service, and NCFS formed the Hemlock Restoration Initiative (HRI). Part of this effort includes protecting hemlocks with chemicals and working to establish biocontrol agents throughout the region. From fall 2018 to spring 2019, 56,920 hemlocks were treated; winter 2019 treatments are ongoing.

Laurel Wilt

The devastating laurel wilt disease was first confirmed in North Carolina in 2011 and is now found in 11 counties in the southeastern part of the state: Bladen, Brunswick, Columbus, Cumberland, Duplin, Lenoir, New Hanover, Onslow, Pender, Robeson, and Sampson Counties.

Surprisingly, laurel wilt made a huge jump and turned up in Tennessee and Kentucky this past summer. This means it could be anywhere within the state. Surveys to track its spread continue but there are no viable management options available.

Thousand Cankers Disease

Since 2012, when thousand cankers disease was first detected in Haywood County neither the fungus nor the walnut twig beetle that carries it have been found in additional counties within the state. A quarantine was implemented in January 2013 that prohibits the movement of regulated materials from Haywood County to unaffected areas of the state.

The NCFS works with the U.S. Forest Service and NCDA&CS Plant Industry Division to trap and survey for newly affected areas in the state. In 2019, 73 traps were set statewide; once again, the walnut twig beetle was not found in additional sites within the state.

Gypsy Moth

The entire state of North Carolina has been monitored for gypsy moth since 1982 through a program of the PID. The 2019 trapping season is complete; 1,019 moths were captured in 507 traps (with a total of 17,612 traps set statewide). This is more captures compared with last year (2018) when 594 moths were captured in 343 traps (18,003 traps set statewide).

Gypsy moth traps (they can be green or orange). Image: Terry Price, Georgia Forestry Commission,

These trap captures, along with winter egg mass surveys done in areas with high capture rates, play a role in 2020 treatment determination. Eight mating disruption treatments totaling 25,390 acres and two Btk treatments totaling 790 acres were proposed to receive treatments in 2020.

The gypsy moth has historically been held at bay from becoming established in North Carolina, with only two counties being quarantined for the pest since 1988 (Currituck County and parts of Dare County).  These two counties remain the only two with a gypsy moth quarantine in place.

Southern Pine Beetle

The southern pine beetle (SPB) has historically been N.C.’s most significant forest insect pest. From 1999 through 2002, SPB killed at least $84 million worth of timber in North Carolina. Since then, beetle activity has been relatively low. In 2017 and 2018, however, activity picked up with 54 and 53 SPB spots totaling approximately 222 and 2018 acres, respectively, on state and private lands. This year, only two small spots of activity were reported with much of the activity documented on federal property in the western part of the state.

Because of their ability to greatly impact our pines, the NCFS regularly monitors for this insect. Each spring, prediction traps are set across the state to assess potential populations. In 2019, the NCFS set 33 SPB prediction traps across the state. These traps, plus additional traps deployed by the USFS, indicated that low SPB populations should be expected across most of the state.

The Southern Pine Beetle Prevention Program, funded through a grant from the U.S. Forest Service, partially reimburses non-industrial private landowners in N.C. for the cost of pre-commercial thinning pine stands. This allows remaining trees to grow with less competition, improves the health of remaining trees, and reduces the stand’s susceptibility to SPB. Since the program began, over 76,000 acres have been treated.

Forest Tent Caterpillar

The forest tent caterpillar is a caterpillar that defoliates bottomland hardwoods. In 2019, North Carolina experienced its fifth consecutive year of forest tent caterpillar outbreak. Through aerial survey, an estimated 104,793 acres was impacted. Trees recovered by summer and no mortality was observed.

Some areas on the Roanoke River were heavily defoliated by the forest tent caterpillar. Image: Kelly Oten, N.C. Forest Service.

Water stress and mortality in trees

In 2019, a series of water-related stress events culminated in tree mortality across parts of eastern and central North Carolina. It all began in September 2018 when Hurricane Florence made landfall at Wrightsville Beach as a Category 1 storm. Rainfall ranged from 15 to 35 inches and floodwaters took some time to recede. Following the storm through early spring 2019, above average rainfall also impacted the region. Many of these rainfall events occurred at least every 5-7 days, keeping the already-saturated soils soaked over this period. This extended saturation led to a decrease in root mass and increase in root-rotting diseases caused by fungi and Phytophthora.

By the middle of April, the weather pattern shifted from one extreme to another and there was little measurable rainfall between then and the end of May. This, coupled with temperatures in the 90°F – 100°F range, resulted in abruptly dry soils and a “flash drought”. By June 1st, many trees were either dead or showing signs of water stress.

Much of the observed mortality was, and continues to be, on oak species on normally drier sites. It is believed that because these trees lost root mass during the period of saturation, they were not able to handle the following drought-like conditions early in the growing season. Many were then attacked by secondary insect or disease organisms.

In September 2019, Hurricane Dorian made landfall in N.C. bringing up to 12 more inches of rainfall in some areas. These ongoing water stress issues will only exacerbate the ongoing water stress exhibited by many N.C. trees.