Invasive Species

There are several invasive and exotic species found on the refuge.  These include common reed or Phragmites (Phragmites australis), alligator weed (Alternanthera philoxeroides), Japanese stiltgrass (Microstegium sp.), parrot feather (Myriophyllum aquaticum), Sesbania (Sesbania exaltata), Japanese honeysuckle (Lonicera japonica), Canada thistle (Cirsium arvense), Chinese privet (Ligustrum sinense), fire ants (Solenopsis invicta), gypsy moth (Mymantria dispar), nutria (Myocastor coypus), European starling (Sturnis vulgaris), house sparrow (Passer domesticus), coyote (Canis latrans), and feral hog (Sus scrofa).

The management of invasive species on the refuge has always been a high priority but the need to implement early detection and rapid response has been exacerbated due to increasing environmental threats and other stresses to the native plant communities.  Climate change and rising sea levels, increasing sources of invasive species (i.e.; Phragmites and alligator weed) adjacent to Refuge lands, and removal of native vegetation due to the Evan’s Road Wildfire have increased encroachment of invasive plant species on the Refuge.  The Evan’s Road Wildfire burned approximately 28,000 acres of native vegetation on the refuge.   The presence of the native plants that slowed the spread of invasive plants is now gone and it is highly likely that invasive plants will reestablish and aggressively encroach large acreages of pocosin habitat before the native plants can recover.  Once large tracts of invasive plants have been established, native plants will be out-competed and will not recover without management intervention.  Salt water intrusion due to rising sea levels in the northwest forks of the Alligator River have stressed native riparian plant communities and contributes to the spread of the highly adaptable invasive species such as Phragmites.  Alligator weed has continually spread from off-refuge sources throughout the canal systems, canal banks and adjacent wet areas of the refuge, including along the Northwest and Southwest Forks of the Alligator River and the Scuppernong River. 

a. Common Reed (Phragmites australis)

The common reed is the most dominant pest plant on the refuge.  The lake margins of Pungo Lake, Lake Phelps and New Lake have great potential for producing high quality waterfowl food plants, but encroaching common reed (Phragmites australis) is a continual challenge.  Phragmites is a persistent and quickly spreading nuisance that out-competes native marsh plant species on lake shores, in marshes, moist soil units and impoundments.  For example, the Phragmites infestation on Pungo Lake was very well established and required at least five consecutive years of herbicide application followed by annual monitoring to maintain the species at a tolerable threshold.  During the monitoring, when smaller patches of Phragmites were detected, they were quickly treated.    When an herbicide treatment for Phragmites was missed one year, it would set back the eradication program by at least two years.   Consecutive annual treatments were particularly important during drought conditions.  The primary route of spread for Phragmites is by rhizomes.  The natural dark water in the lake prevents sunlight penetration into the water column, therefore when the water levels in Pungo Lake were high, the Phragmites would not spread into the lake.  However, during drought conditions when banks were exposed, the Phragmites would send out rhizomes and spread into the lake often tripling the size of the patches within one growing season. 

There is a continual source for Phragmites into Pungo Lake from the west and north banks.  Here, the Phragmites has spread under the canopy of the hardwood swamp forest located adjacent to the lake.  This is an important habitat type for many wildlife species and has limited accessibility for herbicide treatment.   Aerial spraying would kill the forest while ground spraying with heavy equipment would be impossible without severely damaging the habitat.

b. Alligator weed (Alternanthera philoxeroides) and Parrot Feather (Myriophyllum aquaticum)

Alligator weed and parrot feather are exotic aquatic plants which out-compete native vegetation.  Alligator weed has significantly spread and can be found in the majority of the refuge canals located on the east side of the refuge and, for the first time in 2005, on the Pungo Unit.  Large mats of this weed are found floating in the Alligator River, Scuppernong River, and their tributaries, sometimes limiting or preventing accessibility to remote locations of the rivers.  Parrot feather, originally an ornamental aquarium plant, is spreading at a slower rate but is becoming more frequently prevalent in refuge canals and small ponds. 

c. Nutria (Myocastor coypus)

Nutria, an exotic and invasive mammal species, was introduced in the United States in 1899.  Nutria are polyestrus and can produce between 2 to 3 litters per year.  It out-competes the native muskrat and can cause erosion problems around dikes from foraging behavior.  Biologists observe sites that nutria use frequently in the Pungo unit.

d. Fire ants (Solenopsis spp)

Fire ants were introduced into the United States from South America during the 1940s (Tvedten 2005).  This species is associated with disturbed, open habitats, including roadsides, turf, farm fields, and firebreaks.   Fire ant mounds are on average between 10 to 24 inches in diameter and approximately 18 inches in height.  In addition, fire ants will prey on ground nesting birds, herpetofauna, and small mammals.  The presence of large fire ant mounds has caused concerns for introducing ground fires during prescribed burn operations because the mounds are higher and drier than the surrounding terrain, burn more readily, and may carry the fire down into organic soil.  This has resulted in a continual management challenge for the Refuge’s prescribed fire program.

e. Feral Hogs (Sus scrofa)

The exotic feral hogs first appeared on the refuge in the early 2000’s and have significantly spread across the refuge.  The invasive hogs destroy native plants and habitat for Service Trust Species. A multi-year contract would be used to trap and remove these invasive animals from refuge land.