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Insect and Disease
Texas leafcutting ant, Atta texana, on southern pines in Louisiana and Texas. [return]
The Texas leafcutting ant, or town ant, does not eat vegetation per se, but removes the foliage to its subterranean chambers where it uses a substrate on which it cultivates a fungus food. In 1999, it continued to defoliate pine plantations throughout east Texas and central Louisiana on sites with deep sandy soils.
Fraser fir has a very limited range in the Southern Appalachian Mountains and appears almost exclusively in pure stands on the highest mountain peaks or in combination with red spruce at somewhat lower elevations (map). Since the first introduction of the balsam woolly adelgid, approximately 65,000 acres of Fraser fir have been affected. The insect attacks trees of all age classes, but prefers the older fir trees. Adelgid populations were again high in 1999.
Gypsy moth, Lymantria dispar, on hardwoods in Arkansas, North Carolina, Tennessee, and Virginia. [return]
In 1999, aerial surveys in early July failed to detect any noticeable defoliation in Virginia. This is the continuing after effect of an insect pathogenic Entomophaga maimaiga fungus epizootic that caused gypsy moth populations to collapse throughout the eastern range. However, ground surveys located apparently healthy local populations in several mountain and piedmont counties. Consequently, the potential for limited local area defoliation in Virginia is greater for next year than it was for 1999.
In Tennessee, two infestations in Overton and White counties were eradicated. Over 1900 acres in Scott County were sprayed with Bacillus thuringiensis where 224 moths were captured in 1998 and 11 in 1999. Two ground treatments are planned for Sevier and Cumberland Counties in 2000.
In Georgia, gypsy moth infestations were eradicated in the City of Conyers. No new infestations were discovered during 1999.
In North Carolina and Georgia, 23,000 acres in and around the town of Highlands, NC were treated as a part of a gypsy moth eradication program. Follow-up trapping showed very few moths and no treatments are planned there in 2000.
In Arkansas, delimiting and trapping continues in Carroll, Marion, and Newton Counties in the aftermath of an eradication treatment carried out from 1993-95. Only three moths were caught in Newton County in 1999, with none caught in Carroll or Marion Counties. Trapping will continue within an expanded area in Newton County, but no eradication treatments are planned for 2000.
The Gypsy Moth Slow-the-Spread Project moved toward operational status in 1999. Trapping and treatments were carried out in eight states from North Carolina to Wisconsin. Within the boundaries of the Southern Region, 9,090 acres were treated in eastern North Carolina and 24,640 acres in eastern and western Virginia. Additional monitoring and treatment activities will be carried out in 2000.
Hemlock woolly adelgid, Adelges tsugae, on hemlock in North Carolina and Virginia [return]
This insect threatens the entire range of eastern hemlock (map), and is found throughout Virginia wherever hemlock is found in abundance, as well as in five North Carolina counties. No new infested counties were added to the list in 1999. The USDA Forest Service and North Carolina State University cooperated in the evaluation of a release of predaceous beetles in Hanging Rock State Park in Stokes County.
Pink hibiscus mealybug, Maconellicoccus hirsutus, on hibiscus and many other species in Puerto Rico and the U. S. Virgin Islands. [return]
The pink hibiscus mealybug has now spread to over 25 Caribbean islands. It was detected in Puerto Rico in 1997, but has not spread to Florida. The USDA Forest Service and Animal and Plant Health Inspection Service, Plant Protection and Quarantine staffs are working together to rear parasites to control this pest. Mealybug population reductions of 85-90 percent have been achieved at release sites.
Annosus root disease, Heterobasidium annosum on southern pines regionwide [return]
Localized mortality and growth loss occurred throughout the South in 1999 (map). Alabama and Texas reported losses, with the Texas losses occurring mostly in the northeast corner of the state. In South Carolina, annosus root disease combined with drought to cause increased mortality in infected stands.
Fusiform rust, Cronartium quercuum f. sp. fusiforme on southern pines regionwide. [return]
Fusiform rust is the most damaging disease of loblolly and slash pine in the South. Other pine species can also be infected, but little damage or mortality occurs. An estimated 13.8 million acres of loblolly and slash pine have at least 10 percent of trees infected. Georgia is the most heavily impacted state, with 4.6 million acres (49 percent of host type) affected. Texas surveys show that the disease has been on the decline for the past few years. Because of the exceptionally dry weather throughout much of 1999, rust incidence across the region was relatively low for the year (the fungus depends on wet weather for spread and distribution).
Littleleaf disease, Phytopthora cinnamomi, on loblolly and shortleaf pines in Alabama, Georgia, North Carolina, South Carolina, Tennessee, and Virginia. [return]
Littleleaf disease continues to cause growth loss and mortality across the Piedmont areas of the affected states. Shortleaf pine is highly susceptible, while loblolly pine is affected, but at a later age. Many of the stands that were converted from shortleaf to loblolly to reduce the impact of this disease are not reaching their age of susceptibility. These stands are often attacked by bark beetles once weakened by root infection.
Oak wilt, Ceratocystis fagacearum on live and red oaks in North Carolina, South Carolina and Texas. [return]
Oak wilt continues to be a devastating killer in 60 counties in central Texas. Urban, suburban, and rural oaks are affected. Live oaks are the premier tree species in the region and are highly valued for beauty, shade, and wildlife benefits. The Texas Forest Service is in the 12th year of a cooperative suppression project. Since the project’s inception, more than 2.4 million feet (> 450 miles) of barrier trenches have been installed around 1,600 oak wilt infection centers in 34 counties. In the last several years, the Army Corps of Engineers has implemented suppression efforts on 4 central Texas reservoirs. The U. S. Fish and Wildlife Service has initiated suppression efforts at the Balcones Canyons National Wildlife Refuge near Austin, Texas.
Beech bark disease, Neonectria coccinea var faginata on American beech in North Carolina, Tennessee, and Virginia. [return]
Beech bark disease was not found in any additional counties in 1999 (map), but the disease continues to intensify within the currently affected areas. Beech bark disease was first reported in the Great Smoky Mountains National Park in 1994. However, the first mortality in the South was reported as early as the mid-1980’s in northern Virginia. This is well outside the previous known distribution. Tree mortality continues to intensify in Tennessee along the Appalachian Trail in Blount, Cocke, and Sevier Counties within the Great Smoky Mountains National Park. The disease intensified at a greater rate than predicted, and it is spreading down the slopes toward the Cherokee national Forest.
Dutch elm disease, Ophiostoma ulmi, on American elm regionwide. [return]
Scattered to localized mortality continues to occur at low severity levels in urban and wild populations of elm. In Georgia, Dutch elm disease killed hundreds of elms during the 1999 summer drought. Most reports came from larger cities including Atlanta, Augusta, Macon, and Rome.
Butternut canker, Sirococcus clavigignenti-juglandacearum, on butternuts regionwide. [return]
This disease has been in the South at least 40 years (map), and is believed to have killed 3 of every 4 butternuts in North Carolina and Virginia. The fungus kills trees of all ages. Butternut canker is expected to spread and kill most of the resource, including regeneration. The species will be replaced by other species on these sites (e.g., black walnut). It is too early to project the benefits of selection and breeding. However, trees exhibiting resistance have been found in Arkansas, North Carolina, Tennessee, Kentucky and Virginia.
Dogwood anthracnose, Discula destructiva, on flowering dogwoods in Alabama, Georgia, Kentucky, North Carolina, South Carolina, Tennessee, and Virginia. [return]
Dogwood anthracnose continues to intensify within its range, although late season dry weather reduced its impact. No new dogwood anthracnose-infected counties were added to the list in 1999 (map).
Pitch canker, Fusarium subglutinans f. sp. pini (= F. circinatum) on southern pines regionwide. [return]
Only scattered trees across the region are infected, but impacts can be locally significant. In Georgia, pitch canker is associated with pine plantations near chicken houses. The ammonia released from the brood houses creates conditions on the trees conducive to infection. The damage is usually confined to the area within the plantation nearest exhaust fans. All species of pine (slash, longleaf, and loblolly) are affected. Chicken houses are becoming a common sight throughout the coastal plain of Georgia. Thus, problems associated with pitch canker are expected to increase there, especially during droughts. Similar problems have been reported in North Carolina when chicken waste has been used as fertilizer in pine plantations.
Northern Hardwood Decline in Eastern Virginia [return]
Although a small area of upland hardwoods in extreme southern Virginia continues to show decline, research by the Southern Research Station showed in 1999 that claims of widespread decline of northern hardwoods in the Southern Appalachians are highly exaggerated. The report also dispelled the myth that air pollution is a significant causal agent for the hardwood declines in the Appalachians. A summary of the report, written by Dr. Jim Steinman of the USDA Forest Service, is available in news format on the Internet at:
Oak decline, (abiotic and biotic influences) on oaks and other hardwoods regionwide. [return]
The severe summer drought of 1998 continued into 1999, with both the Ozark and Appalachian mountain areas taking the brunt of the moisture deficit. Oaks were particularly hard hit, with North Carolina and Virginia incurring heavy losses on south-facing slopes. Similarly, Tennessee noted increased losses of both red and white oak, with white oaks especially hard hit in the Appalachians. Arkansas reported widespread red oak mortality in the north-central part of the state. In Georgia, oak mortality was heaviest on rocky ridges and side slopes in the mountains. Drought is just one component of oak decline, a syndrome resulting in dieback and mortality of dominant and co-dominant mature oaks. Other causal factors are stressors include frost, defoliation by insects (including the gypsy moth) and secondary pests such as Armillaria root disease and two-lined chestnut borer (Agrillus bilineatus) and hypoxylon canker. Oak decline and gypsy moth have been shown to interact: severe defoliation by gypsy moth can induce oak decline in previously unaffected areas, and in areas of pre-existing oak decline, gypsy moth defoliation causes increased mortality. Host, age, and site conditions also play a role.`
Coneworms, Dioryctria amatalla, D. clarioralis, D. disclusa and D. merkeli on southern pines regionwide.
Coneworms caused a 25 percent cone loss in untreated areas of state seed orchard in Texas in 1999 compared to 5 percent in the treated area. Elsewhere in the South, coneworm numbers were relatively static, except for Florida, where a prevalence of cone rust is contributing to unusually high coneworm populations at the Withlochoochee Seed Orchard.
Pitch canker, Fusarium subglutinans f. sp. pini (= F. circinatum) on southern pines regionwide.
About 5 percent of the cone crop in the Texas state seed orchard was affected by pitch canker.
Seedbugs, Leptoglossus corculus, Tetyra bipunctata on southern pines nationwide.
Seedbugs were abundant in untreated pine seed orchards in Texas in 1999. In other states, seedbug losses were typical.
Southern cone rust, Cronartium strobilinum on slash pine in Florida.
In Florida, unusually high levels of cone rust in slash pine seed orchards continue a problem which has been prevalent over the last several years.
White pine cone beetle, Conopthorus coniperda on white pine regionwide.
Overwintering white pine cone beetle populations increased over 1998 levels in Virginia. In North Carolina, beetle populations were low.
Rhizoctonia needle blight, Rhizoctonia sp. on southern pine seedlings regionwide.
Thanks to improved fungicide treatments, less than 10,000 seedlings were lost to this blight at the Taylor State Nursery in South Carolina in 1999. This compares to 60,000 in 1998.
Damping-off, Fusarium sp. and Pythium sp. on southern pines regionwide.
Damping-off is the most common disease problem facing southern nurseries. Loss of seedlings to damping-off varies greatly from year to year owing to the interaction of pathogenic fungi (species of Fusarium, Pythium, Rhizoctonia, and Phytopthora) and environmental conditions. Seedling losses can be severe when germination is slow due to cold, wet weather. Losses in 1999 were lower than normal due to the very dry weather which inhibits fungus development. Nevertheless, North Carolina reported scattered damping off in southern yellow pine and white pine seed orchards.
White grubs, Phylophaga sp. on southern pine and baldcypress seedlings in Florida.
Abnormally high populations of white grubs necessitated remedial control in Florida. Three separate forest tree nurseries reported significant, although scattered, mortality.
Phomopsis needle blight, Phomopsis sp. on Fraser fir in North Carolina.
The disease was scattered in a North Carolina Fraser fir nursery in 1999.
Wind in Arkansas, North Carolina and Tennessee affecting southern yellow pines and hardwoods.
The year 1999 was a terrible one from a natural destruction perspective in North Carolina. Hurricanes Dennis and Floyd dropped a massive amount of water throughout the whole of eastern North Carolina. Although blowdown damage was not nearly as destructive as other recent Hurricanes (e.g., Hurricane Hugo), the consequences of the devestativg flooding are yet to be fully realized. For example, the North Carolina Division of Forest Resources lost a nursery/seed orchard facility valued at 1.5 million dollars, and the ramifications of not providing the citizenry with seedlings is yet to be calculated. The Division estimates that 71 million ft3of timber were lost to blowdown, with another 80 million ft3 lost to flooding. Almost 15,000 acres of reforestation projects were destroyed. Total direct loss of trees and timber exceeds $89 million. The full impact of these Hurricanes will not be felt for years to come. History shows that southern pine beetle populations often build up to outbreak levels following flooding, and other insects and diseases are also likely to flourish in the storm-stressed forests of the piedmont and coastal plain.
In other incidents, a tornado touched down in west Tennessee, damaging trees along a 20-mile path. Another tornado damaged timber across a 600-acre swath in Handeman County, Tennessee. A severe windstorm in Hot Springs, Arkansas during the summer damaged 3,000 acres of timber. Approximately 500 board feet per acre was damaged.
Fire damage in Florida on various tree species.
The massive wildfires throughout Florida in the summer of 1998 caused mortality, but also predisposed trees to a variety of opportunistic pathogens and insects. While related tree mortality declined dramatically in 1999, Florida resource managers are still alert for secondary insects and diseases in fire-stressed stands.
Hail on various species in Mississippi and South Carolina.
Three spring hailstorms were particularly destructive to forests in Mississippi and South Carolina in 1999. In Mississippi, the single hailstorm defoliated trees in portions of Greene, Jones, Perry, and Wayne Counties in the southeastern area of the state. Because most of the hardwoods had not leafed out, defoliation was confined largely to conifers, although bark damage occurred to twigs and branches of both pines and hardwoods. Field surveys showed that most trees refoliated adequately, and there was little mortality. Some dieback might be expected in the future due to branch canker organisms exploiting the damaged bark.
In South Carolina, two separate hail storms in late April and early May caused defoliation in Aiken, Saluda, and Newberry counties in the western part of the state, and Marlboro County in the east. As in Mississippi, both hardwoods and conifers were impacted, but defoliation was worse among pines. The South Carolina Forestry Commission estimates that 47,700 acres were affected by a minimum of 50% defoliation. The Commission continues to monitor the affected areas for opportunistic insects and disease exploiting weakened trees.
Drought across the region affecting many tree species.
Drought conditions prevailed over much of the South in 1999. Arkansas, Florida, Georgia, Kentucky, Louisiana, Mississippi, North Carolina, Oklahoma, South Carolina, and Tennessee had severe to extreme drought conditions in portions of each state. Texas has suffered drought for three of the past four years. At the end of 1999, over 60 percent of the Southern Region was below normal in precipitation with 20 percent showing a deficit from 3 to 6 inches and 16 percent having a deficit of 6-9-inches. Drought contributed to early defoliation, growth loss, and general tree stress. In many parts of the South, a wet spring caused a rich flush of vegetative growth that later could not be sustained because of the drought. Shallow rooted species on rocky mountain sites were especially impacted in Virginia and North Carolina. Hardwood mortality was particularly striking throughout Virginia, and the secondary impacts to the stressed ecosystems will be felt for years to come.
Many pine plantations planted since the mid-1990's failed due to drought and have been replanted more than once. It is estimated that 35% of the trees planted region wide succumbed to drought in 1999 with losses in extreme drought areas reaching 60%. Overall, it is estimated that 25% of plantations planted in 1999 will require replanting.