1996 Forest Insect and Disease Conditions for the Southern Region
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Most Significant Conditions in Brief
Several weather and climate-related occurrences profoundly affected the health of southern forests in 1996. Moreover, the stresses imposed on the forests by these anomalies may influence the severity of insect and disease activity in 1997 and beyond. Hurricanes Fran and Bertha caused severe damage in North Carolina, but Virginia was also affected. Similarly, Hurricanes Erin and Opal caused widespread tree mortality in Florida, and the state is still witnessing very rapid pine engraver beetle build-ups in the weakened timber. Meanwhile, the problem in east Texas was drought, where the opportunistic pine engraver beetles exploited weakness in water-deprived trees in the Lone Star State. On a brighter note, gypsy moth populations in Virginia virtually collapsed under the influence of the caterpillar-attacking Entomophaga fungus, causing some entomologists to cautiously wonder if they have finally found the "magic bullet." Southern pine beetle populations declined dramatically in 1996. The number of counties and acres affected were down about 2/3 from the record-setting losses of 1995. Hemlock woolly adelgid continues to spread down the Appalachians , threatening not only its host, but also the fragile aquatic ecosystem linked to the cooling effect supplied by hemlock branches overhanging mountain streams.
Perhaps less spectacular, but every bit as insidious and destructive, are the forest diseases. Fusiform rust, oak wilt, Annosum root disease, and oak decline syndrome continue to cause significant losses at various locations throughout the South. The dogwood anthracnose outbreak continues to rapidly spread and intensify, and butternut canker is now believed to have killed nearly 4 of every 5 butternuts in the South.
Status of Forest Insects
Balsam woolly adelgid, Adelges picea, on Fraser fir in No. Carolina, Tennessee, and Virginia.
Fraser fir has a very limited range in the Southern Appalachians, and appears almost exclusively in pure stands on the highest mountain peaks or in combination with red spruce at somewhat lower elevations (Figure 1 50K). Since the first introduction of the balsam woolly adelgid (BWA) in the 1950's, nearly 65,000 acres have been affected. Virtually every sizeable Fraser fir stand in the Appalachians is believed infested. The adelgid prefers larger fir trees, and almost all mature host trees within the affected area have been killed. BWA populations were again high in 1996.
The 1995 outbreak of the cypress looper affected over 450,000 acres in Florida, mostly in the Everglades and Big Cypress Swamp. No reports were received in the second half of 1996, suggesting that the outbreak might have collapsed.
The forest tent caterpillar was active in both Louisiana and Florida in 1996. In Louisiana, tupelo and other bottomland hardwoods were infested throughout the year where the caterpillars defoliated some 245,000 acres, 100,000 of which were completely stripped. Entomologists and foresters estimate that significant growth loss (approximately 50% of radial growth) occurred on 190,000 Louisiana acres (2 of every 5 defoliated acres).
The fruittree leafroller infested some 295,000 acres containing mixed stands of baldcypress in Louisiana.
Loss of approximately 60% of radial growth occurred on about 3 of every four defoliated trees. The number of trees killed is unknown, but is believed to be confined to saplings and pole-sized trees.
Gypsy moth (Asian), Lymantria dispar, on various hardwoods in North Carolina.
In 1993, adult Asian gypsy moths with their characteristic flying females were accidentally released at the Military Ocean Terminal at Sunny Point, North Carolina. Hundreds of male moths (European strain, Asian strain, and hybrids) were captured in pheromone traps after the accidental introduction. The Asian gypsy moth could cause more serious economic and environmental consequences due to its wider range of host species and ability to disseminate through flying. Therefore, a cooperative eradication project with the North Carolina Department of Agriculture and the USDA Animal and Plant Health Inspection Service was initiated in 1994 to deal with the accidental introduction. Some 143,000 acres were treated twice with Bt (biological insecticide) and with Gypchek synthetic virus applied to sensitive areas during 1994. Trapping through a 1,600 square mile area on the North Carolina-South Carolina border in 1994 and 1995 revealed several Asian gypsy moths in pheromone-baited traps. Although the 1994 eradication effort was considered largely successful, supplemental spraying of Bt was conducted in 1995 (6,340 acres) and in 1996 (1,490 acres) to completely eliminate Asian gypsy moth from the area. Trapping across a 1,000 square mile area in 1996 did not yield any further captures of Asian moths, and there are no plans for further treatment in 1997. The post-treatment evaluation will continue in 1997 to confirm that the infestation is eradication, but it will be scaled down to include trapping over a 100 square mile core area only.
Gypsy moth (European), Lymantria dispar, on various hardwoods in Alabama, Arkansas, Georgia, North Carolina, South Carolina, and Virginia.
The fungal pathogen Entomophaga maimaiga caused widespread collapse of gypsy moth populations over generally infested portions of Virginia. Consequently, there was no noticeable defoliation in contrast to 849,000 acres defoliated in 1995. The Commonwealth of Virginia plans to treat less than 100 acres in 1997 (a dramatic decrease from 120,000 acres treated in 1995 and 14,926 in 1996).
Treatment to slow the spread of the gypsy moth continue to be implemented along the expanding front in the 7 million acre Slow-the-Spread (STS) pilot area in the states of North Carolina, Virginia, West Virginia, and Michigan. During 1996, 32,477 acres were treated as part of STS; 1,000 acres of private land in North Carolina; 10,644 acres of private land in Virginia; 16,750 acres of private land in West Virginia, and 3,888 acres of national forest land in Virginia and West Virginia. Approximately 58% of the area was treated with Bt, 38% with a mating disruptant specific to gypsy moth, and 4% with the insect growth regulator diflubenzuron.
Elsewhere, there were isolated infestations in northern Georgia (Fannin County, 800 acres), western North Carolina (Yancy County 2,032 acres), and eastern Tennessee (Unicoi County, 252 acres). Eradication projects were initiated on the listed acreages in each of these areas in 1996. Follow-up trapping was continued on the 1993-95 gypsy moth eradication project in north-central Arkansas. Only a limited number of male moths were caught. Trapping will continue, but no treatments are planned in 1997.
Hemlock woolly adelgid, Adelges tsugae, on hemlock in North Carolina, Tennessee, and Virginia.
The hemlock woolly adelgid continues to threaten eastern hemlock throughout much of its range. (figure 2 44K). As the range expands, the losses within the outbreak continue to rapidly intensify. In the Shenandoah National Park, rangers report an 80 percent decrease in the health of eastern hemlock in just five years. Except for extreme southwest Virginia, virtually the entire state is now infested, with decline and mortality extensive. Much of the hemlock resource is in riparian areas which further compounds the impact of this pest on the ecosystem. Without the cooling effect of the shading limbs, temperatures rise in some streams, making them unsuitable for certain life forms. In 1995, the adelgid was discovered in North Carolina where it now infests hemlock in Stokes, Surry, Rockingham, and Forsyth counties (the latter two having been added in 1996).
Weather stress along the the Gulf and Atlantic coast states precipitated unusually high incidences of pine engraver beetle spots in 1996. In Texas, prolonged drought caused scattered losses across the eastern part of the state. Most losses were evident in single-tree infestations, but occasionally large clumps of trees were attacked. From the Florida panhandle west through coastal Alabama, pine engraver beetle populations were much higher than usual, having been triggered by Hurricanes Erin and Opal. Similarly, Hurricanes Bertha and Fran caused damage in the coastal sections of North Carolina and Virginia, which in turn gave rise to unusually high numbers of pine engraver beetle infestations. These losses were compounded by stresses imposed still earlier in the year when ice storms caused large-scale stem and branch breakage.
For the third consecutive year, red-headed pine sawfly populations (Neodiprion lecontei) caused noticeable to severe (75%-100%) defoliation on longleaf and slash pines in the central Florida counties of Lake, Marion, Polk, and Orange. Although outright tree mortality was rare, it was nonetheless noticeable. Florida entomologists are hopeful that a high incidence of diseased larvae observed in October will signal the final end to the outbreak. Marion County also was the site of heavy blackheaded pine sawfly (Neodiprion excitans) infestations on mature loblolly pine.
Meanwhile, feeding by the loblolly pine sawfly (Neodiprion taedae lineari) and Virginia pine sawfy (Neodiprion pratti pratti) was also higher than normal in middle and East Tennessee.
Southern pine beetle, Dendroctonus frontalis on southern yellow pine southwide.
Southern pine beetle (SPB) populations declined dramatically from the record-setting losses realized in 1995. Overall, the number of infestations declined by 70%, and the outbreak acreage dropped by 2/3. The number of beetle infestations dropped in every state except Tennessee.
Nevertheless, beetle populations still reached outbreak status in parts of North Carolina, South Carolina, Georgia, Alabama, Tennessee, Mississippi, Louisiana, and Arkansas (figure 3 45K). The majority of activity was carryover in the early part of the year from the 1995 outbreaks.
Three factors played an interacting role in the decline of SPB populations: 1) adverse environmental conditions, 2) natural enemies, and 3) aggressive suppression efforts. Two to three weeks of record hot weather in September, followed by two severe freezes in December of 1995 and February of 1996 (temperature drops of over 50 degrees in a 24 hour period) helped reduce SPB populations throughout the South. Evaluation of brood beetles in thin-barked shortleaf pine in Alabama showed 50-75% mortality. A sharp build-up of checkered beetles (a natural enemy of the SPB) also contributed to the decline. Finally, both state and federal land managers were able to mount quick and aggressive suppression programs which enabled them to catch up on a backlog of uncontrolled infestations.
Specific to national forest land, the Ouachita National Forest in Arkansas was hardest hit with over 2,500 SPB infestations and 2,900 MCF of timber salvaged. An area of special concern was the Caney Creek Wilderness near Mena, Arkansas. Eight-eight infestations were tallied in the wilderness. Seven of these required federal action to protect adjacent private forested lands.
On private land in South Carolina, nearly half of the state's counties were in outbreak status in 1996. Nevertheless, by July outbreaks had subsided enough that the Governor was able to disband the disaster council that had been formed in 1995 to expedite salvage of beetle-killed timber. In North Carolina, there was activity in the northeast section of the state. Meanwhile, the SPB outbreak that severely affected the City of Gainesville, Florida collapsed in early 1996. A similar SPB population collapse developed in the Gulf Coastal Plain (Alabama, Mississippi, and Louisiana).
SPB activity continued low in East Texas, an area historically know to experience some of the most dramatic losses in the South. The Texas Forest Service reported only 185 spots statewide, and there were no counties in outbreak status (outbreak county = 1 or more multiple tree infestations per 1,000 acres of susceptible host forest type).
Table 1 shows the number of SPB infestations in 1995 versus 1996 by state. Figure 4 (14K) shows the change in acres infested by state.
Status of Forest Diseases
Annosum root disease, Heterobasidium annosum on southern pines and eastern white pine.
Annosum root disease continues to cause significant losses throughout the South with mortality and growth loss ranging from 2-25% of growing stock on managed high risk stands (figure 5 66K). The disease is most commonly associated with thinned pine plantations on sandy, well-drained sites, but can be found on a variety of sites, soils and forest conditions. Bark beetle infestations frequently occur within infected stands. In 1996, significant new areas of infection were discovered in South Carolina away from the sandhill area where losses are traditionally most severe.
Beech bark disease was reported in the Great Smoky Mountains National Park in 1994. However, the first mortality reported in the Southern Region was not in the National Park, but northern Virginia in the mid-1980's, indicating that the National Park infection center was an isolated introduction well in advance of the previously known distribution. The scale insect associated with the disease is now found in Blount County, Tennessee, but no associated infection has yet been observed. Increase and proliferation of Nectira mortality centers continued in 1996. Figure 6 (41K) shows counties with confirmed infection centers.
Butternut canker, Sirococcus clavigigenti juglandacearan on butternut.
This disease has been in the South for at least 40 years (figure 7 55K), and is believed to have killed 77% of the butternuts in North Carolina and Virginia. The fungus kills large trees, saplings, and regeneration. So widespread and severe is butternut canker that the Digital Arborist has placed a moratorium on the harvesting of healthy butternuts on national forest lands. Some reason for optimism stems from the discovery of canker-free trees in Kentucky, Arkansas, Virginia, and North Carolina -- the latter state providing a large cove of canker-free trees in the mountains which has been preserved as a seed collection area. Still, butternut canker is predicted to spread and kill most of the resource, including regeneration, after which it will be replaced by other species such as black walnut.
Dogwood anthracnose , Discula destructiva, on flowering dogwood in Kentucky, Virginia, North Carolina, South Carolina, Tennessee, Georgia, and Alabama.
Dogwood anthracnose was first discovered in the South in 1987 with the report of 30,000 acres infected in the Cohutta Wilderness of North Georgia. Since then, surveys indicate that 237 counties in seven states are now affected (figure 8 55K). The disease is most prevalent in the mountains, foothills, and upper Piedmont where forest tree damage is most severe higher elevations and in cool, moist elevations at lower elevations. These areas contain site characteristics most conducive to the fungus development.
Scattered to localized mortality continues to occur at generally low severity levels in urban and wild populations of elms.
Fusiform rust, Cronartium quercuum f. sp. Fusiforme on southern pines southwide.
Fusiform rust is the most damaging disease of loblolly and slash pine sin the South. Other pine species may also be infected, but little damage or mortality occurs. The most recent surveys indicate that an estimated 13.4 million acres of loblolly and slash pine have infection levels exceeding 10%. The State of Georgia is most affected with about half its total host type impacted.
In South Carolina, new areas of severe rust infection were discovered in 1996. Since these geographic locales are not classified as highly susceptible to the disease, it is believed explained by an inordinate genetic vulnerability.
Oak decline, abiotic and biotic influences, regionwide.
Oak decline is a syndrome resulting in a dieback and mortality of dominant and comdominant mature oaks. Causal factors are stressors such as drought, frost, defoliation by insects, and secondary insects such as Armillaria root disease and twolined chesnut borer (Agrillus bilineatus). Host, age, and site conditions also play a role. Forest Inventory data analysis in twelve southern states indicates an estimated 3.9 million acres of upland hardwood forest are affected by oak decline -- about 9.9% of the susceptible host type. Average annual mortality volume of oaks on affected sites was nearly double that on non-affected sites. Some of the oak decline reported here is located in areas heavily defoliated by the gypsy moth. The two interact in that pre-existing oak declined area are more vulnerable to mortality following gypsy moth defoliation. Furthermore, severe defoliation can induce oak decline in previously asymptomatic areas. No new local or widespread counts of severe decline were reported in 1996.
Oak wilt, Ceratocystis fagacearum, nearly regionwide
Oak wilt continues epidemic in central Texas, with the number of affected counties now reaching 61. Besides a cooperative state-federal suppression project in the central portion of the state, the U.S. Army Corps of Engineers has a separate suppression initiative around lakes within the same area.
North Carolina reports that oak wilt is intensifying in the western part of the state, specifically in Haywood, Buncombe, Jackson, and Madison Counties. Little new or serious activity was reported in other areas.
Damping-off, Fusarium sp. and others regionwide on southern pines.
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. In 1996, over one-half million seedlings were lost in one Georgia nursery to damping-off.
Insect damage, Noctuidae, Phyllophaga spp. regionwide on southern pines.
Damage by cutworms (Family Noctuidae) and white grubs (Phyllophaga spp) are considered a problem in about 1 of every 3 southern forest tree nurseries.
Rhizoctonia needle blight on longleaf pine in Florida and South Carolina.
Rhizoctonia needle blight destroyed about 200,000 longleaf pine seedlings in a South Carolina nursery and 50,000 longleaf pine seedlings in Florida in 1996.
Lygus bugs, Lygus spp.on sand pine and loblolly pine in Florida and South Carolina.
Seedlings damaged by lygus bug feeding resulted in the loss of a quarter million sand pine seedlings in Florida and 75,000 loblolly pine seedlings in South Carolina.
Prostrate spurge, Euphorbia supina, on hardwood seedlings regionwide.
Prostrate spurge is an aggressive weed which limits hardwood seedling production. It is difficult to control and persists even after soil fumigation. Few herbicides are registered for controlling it in hardwood plantings. A 1996 survey showed that six forest tree nurseries in the South reported this weed as their most significant weed control problem.
Pythium root rot, Pythium spp. on loblolly pine in Mississippi.
About 35,000 seedlings were lost in one Mississippi nursery in 1996.
Seed Orchard Insects and Diseases
Coneworms, Dioryctria amatella, Dioryctria clarioralis , Dioryctria disclusa, Dioryctria merkeli on southern pine cones.
Coneworms continued to cause damage in seed orchards across the South. Data from the Southwide Coneworm Survey showed large populations of the webbing coneworm, Dioryctria disclusa , in the Atlantic coast states.This species was trapped in large numbers in June in orchars in South Carolina. The southern pine coneworm, Dioryctria amatella, and the loblolly pine coneworm, Dioryctria merkeli , occurred in large numbers in October in orchards in Texas, Mississippi, and Georgia. Additionally, first-generation southern pine coneworm occurred in significant numbers in Texas . Coneworm damage significantly reduced the survival of loblolly, longleaf, shortleaf, and slash pine in untreated sources on federal seed orchards in Arkansas, Louisiana, and Mississippi.
Insect pests of white oak acorns, Filbertworm, Cydia latiferreana, acorn weevils, Curculio spp., and Conotrachelus spp., acorn wasp, Valentinia glandulella, and gall wasps, Cynipoidea sp. on white oak acorns in Arkansas.
On monitored research plots on the Ouchita and Ozark National Forests, these insects are responsible for substantial destruction of the white oak acorn crop. The acorn weevils and the filbertworm are the primary pests of white oak in the areas studies. In 1995. Acorn weevils were responsible for approximately 20 percent of the damaged and destroyed acorns in the research area.
Seed bugs, Leptoglossus corculus, Tetyra bipuctata on southern pines regionwide.
Seed bugs continued to cause damage on loblolly, longleaf, shortleaf, and slash pine orchards throughout the South. On monitored orchards in Louisiana and Mississippi , these insects accounted for confirmed losses of 2-28% of harvested seed. These percentages likely underestimate seed bug-caused losses because many empty seeds observed in radiographs of see may also result from seed bug feeding during development of the cones. Additionally, seed bugs cause significant loss due to conelet abortion, especially in longleaf pine.
Insect pests of red oak acorns, Filbertworm, Cydia latiferreana, acorn weevils, Curculio spp., and Conotrachelus spp., pip gall wasp, Callirhytis operator, carpenterworm, Prionxystus robiniae, scale, Eriococcid spp., and stone gall, Callirhytis fructosa on red oak acorns in Tennessee and North Carolina .
The northern red oak seed orchard in Tennessee has suffered an outbreak of the scale Eriococcid spp. over 50% of the orchard trees in 1995. However, an unidentified lady bird beetle, Scymus sp., began attacking the scales in late 1995. By the end of the 1996 growing season, most of the trees in the orchard were scale-free. Trees that were infested in 1995 failed to produce acorns in 1996, thus resulting in a much lower-than-usual harvest. The damage was estimated to exceed 25% of the remaining cone crop at harvest. The filbertworm and stone and pip gall damage was low in 1996.
White pine cone beetle, Conopthorus coniperda on white pine cones in Tennessee and North Carolina.
Overwintering white pine cone beetle popuulations more than doubled the 1995 levels at the Digital Arborist Beech Creek Seed Orchard near Murphy, North Carolina.On three Tennessee Division of Forestry orchards, populations declined. This compares with declining beetle populations on the North Carolina Forest Service orchard near Morganton.
Southern cone rust, Cronartium strobilinum on southern pine cones in Alabama, Florida, and Georgia.
The recent upsurge in infection of slash and longleaf pine cones caused by southern cone rust has apparently subsided, although cone and seed losses in the Florida Division of Forestry's Withlacoochee Seed Orchard at Brooksville were still approximately 20%. Aerial fungicide application shows promise as a control technology.
Pitch canker, Fusarium subglutinans, on slash pine in Florida.
The 1994-5 flare-up of this insect/disease comples has stabilized. No significant activity occurred in 1996.
Ice damage, Louisiana.
Branch damage and topping were common in Central Louisiana in February of 1996 when a severe ice storm coated trees with 1/2-3/4 inches of ice.
Ozone injury, eastern white pine and various bioindicator species regionwide.
Tipburn was observed on eastern white pine throughout the South. Bioindicator plants were used to assess ozone levels in Class I wilderness areas in North Carolina and Georgia. The Class I wilderness areas are surveyed on an annual basis and results are compiled and displayed in tabular format with interpretation as Field Office reports. These reports are used by Air Resource Specialists as tools in permit evaluation. There were slight differences between data collected in 1995 and 1996. Nevertheless, Tennessee reports significantly less ozone damage on white pines on the higher elevation sites on the Cumberland plateau in 1996.
Wind damage, North Carolina, Virginia, Florida, South Carolina, Alabama.
Hurricanes Bertha and Fran caused severe forest damage along the Southeast coast and inland throughout the piedmont and mountain foothills in 1996. In both cases, North Carolina was especially hard hit. Because of the nearness of these two storms in both time (July 12 and September 5) and physical proximity, it is difficult to tally losses attributable to each separately. The North Carolina Division of Forest Resources (NCDFR) and Digital Arborist report that Fran and Bertha affected 52 North Carolina counties, with heaviest losses occuring in Pender and New Hanover Counties in the southern coastal plain. NCDFR estimates that these two storms caused a loss of nearly 8.7 million board feet of sawtimber, collectively valued at 1.3 billion dollars.
Damage by Fran and Bertha was less severe in Virginia, but nonetheless significant. Virginia losses were concentrated in the central and northern Blue Ridge Mountains where hardwoods were badly damaged. There was also noteworthy damage in riparian areas, especially in the Shenandoah Valley.
On the Gulf Coast, Erin and Opal caused widespread damage along the Florida panhandle and Alabama coast which has contributed to heavy pine engraver populations mentioned above.
Indeed, there may be additional latent hurricane-related damage on both the Gulf Coast and in the Carolina-Virginia Atlantic regions owing to the stressed condition of broken, and in some cases, flooded stands.
For more information contact:Wes Nettleton
Forest Health Protection
1720 Peachtree Rd, NW
Atlanta, GA 30367-9102
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