1998 Forest Insect and Disease Conditions for the Southern Region
Note: bold hypertext links within the narratives (e.g., Dogwood anthracnose) will take visitors to the on-line publication, The Health of Southern Forests that displays additional graphics and discusses the biology and southern history of the causal agent in more detail. Not all causal agents are linked. Non-bolded links provide for within-document navigation.
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Below-average rainfall of 1996 and 1997 persisted into 1998, with drought profoundly influencing a number of forest and tree pests – especially in the Appalachian Mountains. Hardwood mortality was especially evident in Virginia and North Carolina where oaks died by the thousands, especially on south-facing slopes and on shallow rooted soils. This dry weather also encouraged outbreaks of a number of opportunistic insects and diseases such as Ips engraver beetles, turpentine beetles, and oak decline syndrome.
Despite greater-than-normal losses to these secondary pests, there was good news on the southern pine beetle and gypsy moth fronts. The year 1998 marked one of the all time lows for southern pine beetle (SPB) with only Alabama marking populations of note. Once again, the gypsy moth showed no noticeable defoliation in Virginia, an apparent continuing beneficial legacy of the insect pathogenic Entomophaga maimaiga fungus that caused gypsy moth populations to collapse in its eastern range.
Foresters, entomologists, and pathologists continued to monitor a number of introduced pests such as beech bark disease, and butternut canker which are particularly virulent. Established diseases such as annosus root disease and littleleaf disease continued to cause heavy losses throughout much of the South.
Black turpentine beetle, Dendroctonus terebrans, on loblolly pine, slash pine, and shortleaf pine regionwide. [return]
Black turpentine beetle activity was at higher-than-normal levels throughout the South due to the summer drought. This insect is most evident in trees stressed by logging damage, root compaction, and similar stressors.
Buck moth, Hemileuca maia, on live oak and other hardwoods in Louisiana. [return]
Buck moth defoliation has been a problem in New Orleans for a number of years. It continues to be locally abundant in the city and of particular concern in the Federal Historic Districts.Fall cankerworm, Alsophila pometria on oaks in North Carolina and Virginia. [return]
Within the City of Charlotte, high populations of the fall cankerworm have been present since 1987. Natural controls, which regulate outbreaks in uninhabited forests, have not been effective in reducing populations in the urban environment. Charlotte has a large number of mature willow oaks that provide an almost unbroken canopy over much of the city. In 1998, 5,800 acres of this resource were treated with Bacillus thuringiensis, a biological insecticide. A separate North Carolina infestation occurred in the western portion of the state along the Blue Ridge Parkway with 12,000 acres defoliated. There was also defoliation by an oak sawfly, Periclista sp., mixed in with this fall cankerworm infestation. Amherst County in Virginia incurred a second straight year of noticeable fall cankerworm defoliation along the Appalachian Trail.
Forest tent caterpillar, Malacosoma disstria on tupelo gum and other hardwoods in Alabama, Florida, Louisiana, North Carolina, and South Carolina. [return]
Defoliation occurred on 88,000 acres of forested wetlands in Ascension, St. James, and St. John Parishes in Louisiana, and 11,800 acres in eastern North Carolina along the Roanoke River. The three-year long outbreak in western Florida collapsed in 1998.
Locust leafminer, Odontota dorsalis, on black locust in North Carolina, Virginia, Tennessee and Kentucky. [return]
Locust leafminer infestations were especially prominent this year in the Southern Appalachian Mountains. Although this summer defoliator rarely causes mortality, the widespread discoloration, especially along the Blue Ridge Parkway, prompted many calls from citizens concerned about the trees.
Fruittree leafroller, Archips argyrospilus in Louisiana on bald cypress. [return]
Defoliation occurred on 616,000 acres of forested wetlands in southeastern and south central Louisiana. Defoliation was severe (>60%) on 290,000 acres a level likely to cause growth loss. Repeated annual defoliation has caused dieback and mortality on sapling and pole-sized cypress in permanently flooded areas. The outbreak is approaching the outskirts of the City of New Orleans.
Nantucket pine tip moth, Rhyacionia frustrana, on loblolly pine and shortleaf pine regionwide. [return]
From Texas to South Carolina, 1998 was the year of the tip moth. Tip moth levels were much higher than in 1997, probably due to the summer drought. Damage was most pronounced in open-grown trees. While the insect rarely causes tree mortality, it can cause significant growth loss. More than half of sampled trees one to five years old were infested in East Texas in 1998. Thirty to forty percent of the tips in the upper branch whorl were attacked. South Carolina experienced heavy damage in August as large areas had 100% of terminals and laterals infested. The extended drought allowed development of an unprecedented fourth generation of Nantucket pine tip moths in the central part of Tennessee. This resulted in spectacular damage in the Cumberland Plateau.
Pine engraver beetles, Ips calligraphus, Ips grandicollis, and Ips avulsus, southwide on southern yellow pines. [return]
The severe drought conditions during the growing season across the entire South led to higher-than-normal levels of Ips engraver beetle activity. Small groups of Ips-killed trees were scattered throughout the forest stands making losses difficult to quantify. Activity was low in Mississippi until early fall when a sharp increase was reported, much of it in young plantations. Ips were particularly troublesome in the Carolinas and southwest Tennessee. South Carolina infestations were generally confined to overstocked loblolly pine plantations but rarely exceeded 25 trees. In North Carolina, losses were severe in the Piedmont and also in shallow-rooted pines in the mountains where drought stress was exacerbated. Significant mortality was also reported in Florida where summer fires predisposed large tracts of forestland to attack.
Pine sawflies, Neodiprion spp. On southern pines in Florida, Georgia, Kentucky, Mississippi, North Carolina, and Virginia. [return]
Mississippi recorded several early season defoliations of the blackheaded pine sawfly, Neodiprion excitans, in the northeastern part of the state. Virginia pine sawfly, Neodiprion pratti pratti, was also active in the North Carolina Piedmont and Kentucky on Virginia and shortleaf pine. In Florida, Georgia, and Kentucky, the redheaded pine sawfly, Neodiprion lecontei, caused scattered defoliation.
Reproduction weevils, Hylobius pales and Pachylobius picivorus in Texas on southern pines. [return]
Damage caused by reporoduction weevils (Pales [pronounced “pay-leez”] and pitch-eating weevils) was locally significant in Texas in 1998. Jasper, Newton, and Panola counties were most affected. Average weevil mortality on 18 sites was 23 percent compared to only 10 percent in 1997. Localized areas had as much as 50-60 percent mortality.
Southern pine beetle, Dendroctonus frontalis, on southern yellow pine in Alabama, Arkansas, Florida, Georgia, Louisiana, Mississippi, North Carloina, South Carolina, Tennessee, Texas, and Virginia. [return]
This past year was one of the all time lows for southern pine beetle populations. Regionwide, the number of spots in 1998 declined 10 percent from the 1997 level, but the number of acres in outbreak status declined by 25% (Chart). The only area with significant numbers of beetle spots was south central Alabama (map). On state and private land in Texas, there were no reported infestations during the entire year.
In Alabama, SPB populations started high in 1998 and declined only slightly during the summer drought. Forty-two of Alabama’s 67 counties had outbreak populations levels at some point during the year. The highest populations were along the interface of the coastal plain and Piedmont. In South Carolina, beetle populations increased in the fall with the highest populations occurring in the Piedmont section. The SPB outbreak in North Carolina in the area of the coastal plain affected by Hurricane Bertha and Fran continued on in the early part of 1998, but subsided. The same is true in Florida where the 1997 outbreak in the Ocala area dropped off to nothing. There have been no reports of increased beetle activity after the severe summer fires in Florida.
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 it as a substrate on which it cultivates a fungus food. In 1998, 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 1998.
No noticeable defoliation occurred in Virginia in 1998. The is the continuing after effect of an Entomophaga maimaiga fungus epizootic that caused gypsy moth populations to collapse throughout the eastern range. However, there is some indication that gypsy moth populations have begun to rebuild in a few localized areas. There will be one gypsy moth suppression project in Prince William County in Virginia.
In North Carolina, the isolated gypsy moth infestation continued around the town of Highlands. This is near the North Carolina- South Carolina border. An eradication project covering 23,000 acres is planned for 1999 that will involve treating areas in both North Carolina and Georgia.
In Arkansas, delimiting trapping continues in Carroll, Marion, and Newton Counties in the aftermath of an eradication treatment of in infestation in 1993-95. Only a limited number of male moths were caught. Trapping will continue, but no treatments are planned for 1999.
Widespread detection trapping also continues in uninfested states with occasional isolated catches reported.
Treatments to slow the spread of gypsy moth continue to be implemented along the expanding front in the 7-million acre Gypsy Moth Slow-the-Spread Pilot Project area in the states of North Carolina, Virginia, West Virginia, and Michigan. About 60 percent of the areas was treated with the biological insecticide Bacillus thuringeiensis, and 40 percent with a mating disruptant specific to the gypsy moth.
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. Caswell County, North Carolina was added to the list of infested counties in 1998.
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 the mainland of the United States. The Digital Arborist 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.
Localized mortality and growth loss occurred throughout the South in 1998 (map). Alabama and Texas reported losses in 1998, while in South Carolina, heavy infection necessitated the clearcutting of 2,000 acres of loblolly and longleaf pine. In several states, pines planted under the Conservation Reserve Program are now being thinned and becoming infected.
Fusiform rust is the most damaging disease of loblolly and slash pine in the South. Other pine species may 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 affected. Georgia is the most heavily impacted state, with 4.6 million acres (49 percent of host type) affected. Early spring rains in South Carolina contributed to an increase in rust infection in some localized areas.
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 11th year of a cooperative suppression project. In the last three years, the Army Corps of Engineers has implemented suppression efforts on four central Texas reservoirs. In South Carolina, oak wilt was confirmed for the first time in Aiken County where it was found on several live oaks. This is also the first known occurrence of the disease on live oak outside of Texas. In North Carolina, 15 new disease centers were detected via 1998 summer aerial surveys, primarily in Haywood and Buncombe Counties.
Beech bark disease, Nectria coccinea var faginata on American beech in North Carolina, Tennessee, and Virginia. [return]
Beech bark disease (map) was not found in any additional counties in 1998, 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. In 1998, 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.
This disease has been in the South (map) at least 40 years, 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. A cove with a large number of canker-free and cankered trees in western North Carolina has been converted to a seed collection area with potentially resistant trees being propagated in an east Tennessee nursery. In 1998, a relatively large cluster of apparently uninfected trees in the North Carolina Piedmont was found on a Forest Health Monitoring plot.
Dogwood anthracnose continues to intensify within its range (map), although late season dry weather reduced its impact. Tennessee added seven new counties to the known range of this pest: Lincoln, Macon, Marshall, Moore, Smith, Summer and Trousdale Counties.
Pitch canker, Fusarium subglutinans f. sp. pini (= F. circinatum) on southern pines regionwide. [return]
Pitch canker has returned to endemic levels after a major increase in 1995. Scattered trees across the Region are affected, but impacts can be locally significant. Pitch canker is increasing in southern Mississippi, particularly Perry County. In North Carolina, pitch canker is becoming especially serious where sewerage or animal waste have been applied to forest tracts as fertilizer.
Northern Hardwood Decline in Eastern Virginia [return]
In 1997, there were reports of mortality and dieback to the northern hardwood forest type at relatively high elevations along the Appalachian Trail. The Forest Service conducted an aerial survey of this forest type in North Carolina and Tennessee. The conclusion was that while there are small areas of notable northern hardwood decline and tree death in the southern Appalachian Mountains, there is no indication that this condition is widespread or severe, or that it is in excess of that expected for forests with similar disturbance history.
Severe summer drought throughout the region has caused death or decline of oaks and other trees. Arkansas and Virginia were especially hard hit, with oaks dying throughout the state. Oak decline is a syndrome resulting in dieback and mortality or dominant and co-dominant mature oaks. Causal factors are stressors such as drought, frost, defoliation by insects, including the gypsy moth and secondary pests such as Armillaria root disease and two-lined chestnut borer (Agrillus bilineatus). 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. Analysis of forest inventory data in 12 southern states shows that 3.9 million acres of upland hardwood forests are affected by oak decline – about 9.9 percent of the susceptible host type. Average annual mortality volume of oaks on affected sites was 45 percent higher than on unaffected sites.
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 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.
About 5 percent of the cone crop in the Texas state seed orchard was affected by pitch canker.
In a Texas seed orchard, 13 percent of the seed was lost in untreated areas. In other states, seedbug losses were typical.
Heavy rust-caused cone loses in slash pine seed orchards continues a trend prevalent over the last several years.
Overwintering white pine cone beetle populations increased over 1997 levels in Virginia.
Despite better fungicide treatment regimens, 60,000 seedlings were lost to this blight at the Taylor State Nursery in South Carolina.
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. Although the spring of 1998 was conducive to damping-off, warm and dry conditions throughout the rest of the growing season ameliorated losses to this condition. In 1998, an estimated 2 percent of nursery seedlings lwere lost to this condition across the South.
This disease killed 20,000 red cedar seedlings in Virginia.
Wind in Texas affecting southern yellow pines and hardwoods
A severe windstorm associated with a strong cold front hit east Texas on February 10, 1998 and caused widespread damage in Angelina, Nacogdoches, Polk, San Augustine, and Shelby Counties. The storm affected 103,000 acres of national forestland and 32,000 acres of private land. The storm coupled with severe summer drought contributed to the high Ips beetle populations later in the year.
Fire in Florida affecting many tree species.
Massive wildfires throughout Florida in May, June, and July not only caused mortality, but has also predisposed trees to a variety of opportunistic pathogens and insects. The long- term effects of the fire will be monitored throughout 1999.
Drought across the region affecting many tree species.
Despite a wet 1998 spring, exceptionally dry weather was the norm throughout the summer and fall across the South. The wet spring stimulated much vegetative growth, which later could not be sustained because of the drought. The drought contributed greatly to the incidence of other pests such as oak decline and Ips engraver beetle attacks. Shallow-rooted species on rocky mountain sites were especially impacted in Virginia and North Carolina. Hardwood mortality was especially striking throughout Virginia, and the secondary impacts to the stressed forest ecosystems are expected to be felt for years to come. The drought was also responsible for the seedling mortality in pine regeneration areas covering an estimated 158,000 acres across the South. The estimated cost of replanting these areas is $20 million.
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