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The balsam woolly adelgid, Adelges piceae (Ratzeburg) (Homoptera: Adelgidae), is a major pest in Fraser fir, Abies fraseri (Pursh) Poir, Christmas tree plantations in the southern Appalachian Mountains. Shortly after eclosion, A. piceae larvae insert their stylets into intercellular bark tissue to ensure a constant feeding source from cortical parenchyma cells (Balch 1952, Can. Dept. Agric. Publ. No. 867, 76 pp.). Thereafter, the developing adelgid is attached at that site for the remainder of its life (Balch and Carroll 1956, Can. Dept. Agric. Publ. No. 977, 7 pp.). Insects that use a piercing-sucking mode of feeding, such as adelgids, elicit a response similar to that of fungal and bacterial plant pathogens (Walling 2000, J. Plant Growth Regul. 19: 195–216; Bernards and Spohr 2008, Pp. 189–211, In Schaller, A. (ed.), Induced Plant Resistance to Herbivory, Springer Science, Stuttgart, Germany). The synthesis of new compounds or structural barriers after herbivore-induced damage occurs, including the accumulation of proteins and secondary metabolites, are characteristics of induced defenses (Bernards and Spohr 2008). For example, the formation of cell wall modifications can be induced by wounding and herbivory (Ginzberg 2008, Pp. 131–146, In Schaller, A. (ed.), Induced Plant Resistance to Herbivory, Springer Science, Stuttgart, Germany). Host resistance mechanisms include rapid accumulation of monoterpene and juvabione-related compounds, the production of secondary periderm (Mullick 1975, Can. J. Bot. 53: 2443–2457; Hain et al. 1991, Pp. 271–287, In Baranchikov, Y.N., Mattson, W.J., Hain, F.P., Payne, T.L. (eds.), Forest Insect Guilds: Patterns of

The optimal environmental conditions for rearing the balsam woolly adelgid, Adelges piceae (Ratzeburg) (Hemiptera: Adelgidae), on its natural host, Fraser fir, Abies fraseri (Pursh) Poir, was determined by varying temperature, photoperiod, and humidity as well as by evaluating texture and geotaxic preferences. Five locations with a set temperature and relative humidity (RH) were chosen to test for optimal environmental conditions: three environmental chambers maintained at 17, 20, and 25°C with 75% RH; an insectary maintained at 21.1°C and 72% RH; and a greenhouse with varying temperature and RH levels. Overall, 20°C appeared to be the optimal temperature for development, and 25°C was the least favorable of the temperatures tested. Comparing Fraser fir cuttings to seedlings, seedlings (15.51/cm) were five times more infested than cuttings (3.02/cm), and the percentage of adult survival was higher on seedlings (67%) than on cuttings (17%). The highest percentage of adelgids reaching full developme...

The overwintering sites and seasonal abundance of phytoseiid mites were determined in North Carolina Fraser fir Christmas tree plantations. Potential overwintering sites for the mites include Fraser fir branches, Fraser fir bark, surface litter composed of Fraser fir needles, a mixture of fescue grass (Festuca spp.) and nimblewill (Mhlenbergia schreberi J.F. Gmelin.), mixed herbaceous debris from the previous growing season, and a monocultural cover crop of white clover (Trifolium repens L.). Twelve species of mites (n = 414) in the family Phytoseiidae were collected. Arrenoseius morgani (Chant) (n = 160), Typhlodromips sessor (DeLeon) (n = 156), and Typhlodromalus peregrinus (Muma) (n = 34) were the most abundant. During the spring and summer Fraser fir plantations with a ground cover consisting of white clover were compared with plantations with bare ground to assess the abundance and species composition of phytoseiid mites. A total of 512 phytoseiids representing 8 species was collected. Phyto...

A hypothesis is presented that atmospheric deposition is predisposing Fraser fir to balsam woolly adelgid (BWA)-caused mortality and that the amount of mortality in six Fraser fir zones is a reflection of the amount of atmospheric deposits in each zone. We argue that Fraser fir is a highly sensitive species to atmospheric pollutants, that BWA increases that sensitivity, and that the Fraser fir ecosystem is a primary depository of such pollutants. Alternative hypotheses are also discussed. It is likely that a number of factors, including patterns of atmospheric deposits, contribute to Fraser fir mortality patterns in the southern Appalachians. Zusammenfassung Die Bedeutung der Ablagerungen von Luftschadstoffen fur die Tannenmortalitat, verursacht durch die Wollaus Adelges piceae (Ratz.) (Hemipt., Adelgidae): Eine Hypothese Es wird eine Hypothese vorgestellt, die in der Ablagerung von Luftschadstoffen einen wesentlichen, auf die Mortalitat von Fraser-Tannen, verursacht durch Adelges piceae einwirkenden Faktor sieht. Der Umfang der Mortalitat in sechs Tannenzonen entsprach dem Umfang der jeweiligen Schadstoffbelastung. Es wird argumentiert, das die Fraser-Tanne hochempfindlich gegenuber Immissionen sei, das die Wollaus diese Empfindlichkeit noch erhohe, und das das Tannen-Okosystem einen primaren Ablagerungsort fur diese Schadstoffe darstelle. Alternativen hierzu werden erortert. Es ist wahrscheinlich, das eine Anzahl von Faktoren, einschlieslich der Luftschadstoffe zur Tannensterblichkeit im sudlichen Appalachengebirge beitragt.

Des sapins de Fraser, Abies fraseri (Pursh) Poir., furent cultives en serres et dans quatre sites au champ dans la partie sud des Appalaches dans le but d'etudier les effets des infestations du puceron lanigere, Adelges piceae (Ratz.). Le renflement de la tige principale a ete utilise comme indicateur de la production de bois anormal («rotholz») qui est declenchee par une infestation. Dans trois des quatre sites, la tige principale des semis infestes etait plus renflee que celle des semis sains. L'importance du renflement cause par le puceron lanigere n'etait generalement pas influencee par la provenance des graines (descendance uniparentale), la provenance du sol (haute ou faible altitude), ni par l'interaction de ces facteurs. Dans deux des quatre sites, l'infestation etait associee a une augmentation significative du ratio racines:tige. La variabilite du ratio racines:tige et du poids sec total des semis etait influencee par des interactions entre l'infestation, la provenance du sol et la provenance des graines. Ce resultats demontre que les caracteristiques genetiques des arbres et l'environnement jouent tous deux un role important dans la reponse en croissance des semis de sapin de Fraser infestes. Les resultats de l'etude en serres montrent que le puceron lanigere pourrait etre represente par deux biotypes ou plus dans la partie sud des Appalaches. L'augmentation du poids et du diametre de la tige etait relativement forte chez les semis du mont Mitchell infestes par le puceron lanigere du mont Rogers, et relativement faible lorsqu'ils etaient infestes par le puceron lanigere du mont Mitchell. L'inverse etait vrai pour les semis du mont Rogers. Dans l'ensemble ces resultats suggerent que l'environnement est probablement plus important que les caracteristiques genetiques des arbres ou de l'insecte pour expliquer pourquoi autant d'arbres infestes sont morts dans les montagnes Noires de la Caroline du Nord

Since its introduction into the Southern Appalachians in the 1950s, the balsam woolly adelgid, Adelges piceae Ratzeburg (Hemiptera: Adelgidae), has devastated native populations of Fraser fir, Abies fraseri (Pursh) Poir. (Pinales: Pinaceae), and has become a major pest in Christmas tree plantations requiring expensive chemical treatments. Adelges piceae—resistant Fraser fir trees would lessen costs for the Christmas tree industry and assist in the restoration of native stands. Resistance screening is an important step in this process. Here, four studies directed toward the development of time— and cost—efficient techniques for screening are reported. In the first study, three methods to artificially infest seedlings of different ages were evaluated in a shade—covered greenhouse. Two—year—old seedlings had much lower infestation levels than 7 year—old seedlings. Placing infested bark at the base of the seedling was less effective than tying infested bark to the seedling or suspending infested bolts above the seedling. Although the two latter techniques resulted in similar densities on the seedlings, they each have positive and negative considerations. Attaching bark to uninfested trees is effective, but very time consuming. The suspended bolt method mimics natural infestation and is more economical than attaching bark, but care must be taken to ensure an even distribution of crawlers falling onto the seedlings. The second study focused on the density and distribution of crawlers falling from suspended bolts onto paper gridded into 7.6 × 7.6 cm cells. Crawler density in a 30 cm band under and to each side of the suspended bolt ranged from 400 to over 3000 crawlers per cell (1 to 55 crawlers per cm2). In the third study, excised branches from 4 year—old A. fraseri and A. vetchii seedlings were artificially infested with A. piceae to determine whether this technique may be useful for early resistance screening. The excised A. fraseri branches supported complete adelgid development (crawler to egg—laying adult), and very little adelgid development occurred on A. vetchii branches. The fourth study compared infestation levels and gouting response on excised versus intact branches of 4 year—old A. fraseri seedlings from three different seed sources, and excised branches from 4 year—old and 25 year—old trees. There were no differences in infestation levels between excised versus intact branches nor in very young versus mature trees; gouting response was observed only on intact branches.

Response of Fraser fir, Abies fraseri (Pursh) Poiret, to the balsam woolly adelgid, Adelges piceae (Ratzeburg), was evaluated by studying wood cores and bark samples taken from six sites near Mount Rogers, VA, and five sites in the Black Mountains of North Carolina surrounding Mount Mitchell. For comparison, samples were also collected from silver fir, Abies alba Miller, at four sites in the Black Forest of Germany. Average A. piceae densities were higher on trees at Mount Rogers than on Mount Mitchell trees. Proportions of trees producing abnormal wood in response to low or moderate A. piceae densities was greater for Mount Mitchell trees than for trees at Mount Rogers. Results from Mount Rogers support observations made for other fir species that A. piceae infestation induces outer bark formation, leading to tree recovery. Outer bark formation in trees from the Black Mountains and the Black Forest of Germany was not correlated with A. piceae density. There was indirect evidence that the outer bark measured in Mount Mitchell trees was incompletely formed, with an indistinct boundary layer between living and nonliving bark layers.

The phytoseiid predators Neoseiulus fallacis (Garman) and Metaseiulus occidentalis (Nesbitt) were reared together and fed on Tetranychus urticae Koch to determine the possibility of coexistence and the effect of vapor pressure deficit on the two species. Additionally, developmental times for the two predators feeding on the spruce spider mite, Oligonychus ununguis (Jacobi), were determined at 14°C and vapor pressure deficits of 1, 4, 6, and 10 millibars (mb). N. fallacis and M. occidentalis respond to vapor pressure deficit in essentially opposite ways. In the interaction treatments, populations of N. fallacis reproduced rapidly at low vapor pressure deficits (high atmospheric moisture) but vapor pressure deficits of 10 mb or greater severely limited population growth of this species; M. occidentalis populations grew more readily at higher vapor pressure deficits (>10 mb). At 14°C, egg mortality for M. occidentalis was 25, 10, 20, and 45% at 1, 4, 6, and 10 mb, respectively; egg mortality for N. fallacis at these respective vapor pressure deficits was 25, 0, 15, and 80%. At 14°C, developmental periods for immature stages of N. fallacis among vapor pressure deficits were significantly different in the egg and larval stages and in the egg stage for M. occidentalis . N. fallacis is directly subject to the physical environment (vapor pressure deficit effect on egg mortality) whereas M. occidentalis is subject to differences in survival responses (less prolific than N. fallacis at a given vapor pressure deficit and temperature). The differential response of the two predators suggests that releases of both species to control O. ununguis on Fraser fir in western North Carolina can be optimally timed based on humidity conditions.

Potential sapwood flow rates were measured for Fraser fir sterns that previously had been infested by the balsam woolly adelgid. The amount of abnormal wood produced during infestation was inversely related to the flow rate and linearly related to the amount of heartwood area. These results support the hypothesis that abnormal wood production associated with adelgid infestation can lead to water stress in the crowns of infested trees. The data also suggest that adelgid infestation accelerates the formation of heartwood.

Fraser fir (Abiesfraseri (Pursh) Poir.) seedlings were artificially infested with balsam woolly adelgid, Adelgespiceae (Ratz.), then subjected to drought-stress treatments. Infestation caused a distinct swelling in the main stem, caused by the accumulation of abnormal wood (i.e., "rotholz"). As expected, drought stress reduced diameter growth in the main stem. However, the reduction in wood increment caused by drought stress was relatively small for infested seedlings as compared with uninfested seedlings, owing to the production of rotholz. This implies that infested trees expend considerable energy and nutrients for the production of poorly functioning wood even during periods of stress. The implications of this research for interpreting patterns of tree mortality in the southern Appalachian Mountains are discussed.

Research on tree decline has shown that the proportion of sapwood area to heartwood area is an important measure of tree health. Infestation by the balsam woolly adelgid (BWA), Adelges piceae (Ratz.), causes the formation of abnormal wood, which is thought to conduct sap poorly. BWA infestation is also associated with lower (more negative) xylem pressure potentials and increased areas of heartwood. We hypothesize that lower pressure potentials (a consequence of abnormal wood production) increase the rate of cavitation (gas-filling) of sapwood tracheids, thereby accelerating heartwood formation. If this hypothesis is correct, adelgid attack causes loss of functional sapwood both directly and indirectly. There is evidence that the balsam woolly adelgid is an important factor causing the decline of Fraser fir, Abies fraseri (Pursh) Poiret, in the southern Appalachians. However adelgid damage is probably interacting with many other environmental factors to cause reductions in per cent sapwood area. Determining the relevance of this pest to tree decline can be accomplished by examing the relationship that exists between adelgid infestation, increment growth, and per cent sapwood area.

Single applications of 0.51% insecticidal soap/diazinon (40%:0.4% AI), 0.52% insecticidal soap/methoxychlor (38.7%:3.0% AI), 0.01% fenvalerate, 0.01% permethrin, and one and two applications of 0.63% Safer’s insecticidal soap were tested against the egg, crawler, nymph, and adult of the balsam woolly adelgid, Adelges piceae (Ratzeburg). With the exception of the soap/methoxychlor, all materials appeared to be effective against nonegg stages. The residual toxicity of fenvalerate and permethrin killed all nonegg stages, resulting in no egg production in later samplings. Fenvalerate and insecticidal soap did not adversely affect nontarget organisms in the litter. Fenvalerate showed no phytotoxicity applied to Fraser fir, Abies fraseri (Pursh) Poir. Christmas trees at 0.01, 0.02, 0.04, and 0.08% concentrations. A soap discoloration study indicated that succulent foliage (June growth) may be sensitive to soap treatments, but multiple sprays of either high or low concentrations may be used with little discoloration at times later than June.

A field experiment was conducted during 1984–85 to evaluate the influence of six ground covers on white grub (Coleoptera: Scarabaeidae) densities and feeding damage to roots of young Fraser fir ( Abies fraseri (Pursh) Poir.) Christmas trees in the southern Appalachians. The three dominant grub species were Phyllophaga anxia (LeConte) Glasgow, Phyllophaga fusca (Froelich) Glasgow, and Polyphylla comes Casey. Ground covers were fescue ( Festuca elatior L. cv. Kentucky-31), orchardgrass ( Dactylis glomerata L.), Kentucky bluegrass ( Poa pratensis L.), red clover ( Trifolium pratense L.), subterranean clover ( Trifolium subterraneum L. cv. Mt. Barker), and dead sod–entire plot herbicide. Mowed grass plots supported the densest grub populations ($\bar x$ = 32.3 to 43.0 grubs per m2) when compared with clover and dead sod plots ( x ¯ = 13.3 to 16.1 grubs per m2), and contained fir trees with the most severe feeding damage to roots, poorest health, and lowest wood volumes.

Summary Hypotheses of forest decline are summarized. Stressed trees may be a more suitable food source for invertebrate herbivores than unstressed trees because stress causes an increase in the tissue content of soluble nitrogenous compounds. There is reasonable correlative evidence that air pollutants influence the outbreak patterns of forest insect species. In some cases, formerly innocuous insects may become pests. The occurrence of specific insect pests with specific air contaminants is reviewed. Emphasis is placed on the decline of Fraser fir (Abies fruseri (Pursh) Poir.) in the southern Appalachians and the occurrence of the balsam woolly adelgid. Variable mortality patterns of Fraser fir may be caused by locally distributed air pollutants acting in combination with other types of stress including that caused by the adelgid.

Bark of mature Fraser fir, Abies fraseri (Pursh.) Poir, from Mt. Mitchell, N.C., and Mt. Rogers, Va., was artificially wounded and treated with chemicals (naphthalene acetic acid, pectinase, or todomatsuic acid) suspected to be in association with balsam woolly adelgid, Adelges piceae (Ratzeburg), attack. α-and β-pinene, δ-3-carene, and limonene were the only monoterpenes found in Fraser fir at both locations. There were no differences in monoterpene content between wounds and controls at either site, but bark samples from firs at Mt. Rogers contained lower percentages of α-pinene and δ-3-carene than firs at Mt. Mitchell. Sapwood tissue beneath adelgid wool masses at the above sites and Roan Mt. were also analyzed for monoterpenes. Infested trees at Mt. Rogers contained less α and β-pinene than uninfested controls. There were no differences at Mt. Mitchell or Roan Mt.

Field experiments were conducted in 1982, 1983, and 1984 to evaluate the efficacy of several insecticides for controlling white grubs infesting Fraser fir, Abies fraseri (Pursh) Poir., Christmas trees and pastureland scheduled for fir plantings, and to evaluate insecticide phytotoxicity. The white grub complex consisted primarily of three species: Pyllophaga anxia (LeConte) Glasgow, P. fusca (Froelich) Glasgow, and Polyphylla comes Casey. Mean pretreatment white grub population densities ranged from 20.8 to 77.8 grubs per m2. Isazophos, diazinon, carbofuran, carbaryl, trichlorfon, chlorpyrifos, and isofenphos demonstrated a wide range of effectiveness in reducing populations while showing no phytotoxicity to grass sod or fir. Isazophos and diazinon applications provided the highest levels of control.

A total of 89 Fraser fir, Abies fraseri Pursh. (Poir.), from seven locations in the southern Appalachians were tested for non-suberized impervious tissue (NIT) at artificial wound sites. All trees except one formed NIT in a time period that was considered normal (3 weeks), with no delays due to tree age, location or presence of balsam woolly adelgid, Adelges piceae (Ratz.). Although most Fraser fir react to adelgid attack by forming “rotholz” (red wood), a number of infested trees showed no visual signs of rotholz formation.

Comparisons of the seasonal history of balsam woolly adelgid, Adelges piceae (Ratzeburg), populations were made at five elevations in the southern Appalachians. Populations in three natural stands of Fraser fir, Abies fraseri (Pursh) Poir, above 1,760 m produced two generations in 1983. The adelgids infesting a small plantation of mature fir at 1,219 m emerged from winter diapause a month sooner than those in natural stands, but most of the population completed two generations. A third generation was found in the adelgid population infesting a cultivate Fraser fir Christmas tree plantation at 853 m.

A field experiment was conducted in 1984 and 1985 to evaluate the effects of four weed control practices on white grub densities and feeding damage to roots of young Fraser fir, Abies fraseri (Pursh) Poir., Christmas trees. Variations in wood volume and health were also evaluated. The white grub complex consisted primarily of three species: Phyllophaga anxia (LeConte) Glasgow, Phyllophaga fusca (Froelich) Glasgow, and Polyphylla comes Casey. Cultivation practices were: entire-plot herbicide, not mowed; 0.6-m-wide herbicide-treated strip in tree rows only, mowed; sod, mowed, no herbicide; and sod, not mowed, no herbicide. Mowed sod plots supported the densest grub populations ( x = 44.3 grubs per m2) and contained trees with the most severe root damage, lowest wood volume, and poorest health. Plots treated entirely and in strips with herbicide contained the healthiest, least damaged trees with the highest wood volumes, while supporting mean grub densities of 13.9 and 21.9 grubs per m2, respectively. Grubs in herbicide-strip plots were usually found in the mowed, grassy areas. Plots that were not mowed supported a mean density of 18.5 grubs per m2, and contained trees with moderate to heavy root damage.

During the summer of 1983 and 1984, Fraser fir trees at three locations in the southern Appalachians were wounded and treated with napthalene acetic acid (NAA), pectinase and todomatuic acid. The latter two chemicals and an auxin-like compound similar to NAA are associated with balsam woolly adelgid infestations. None of the chemical treatments delayed formation of non-suberized impervious tissue (NIT) at the wound sites. In most cases, NIT formed within 21 - 27 days after wounding, even when not treated.

Experiments were conducted on Fraser fir,Abies fraseri(Pursh) Poir, seedlings or cut terminals. Results indicate thatOligonychus ununguis(Jacobi) responds most favorably to temperatures approximating 26 °C and to relative humidity levels approaching 50 to 60%. Developmental time, time to 50% mortality, net reproductive rate, mean generation time, intrinsic rate of natural increase, finite rate of increase, and days for populations to double were computed for each temperature and relative humidity regime. Simulated rainfall severely limits population density on Fraser fir seedlings.

The effectiveness of the phytoseiid predator Neoseiulus fallacis in controlling population growth of the spruce spider mite, Oligonychus ununguis was examined in the laboratory. Development and fecundity of N. fallacis under various relative humidity levels were also studied. Under controlled conditions, N. fallacis significantly limited population growth of O. ununguis on Fraser fir seedlings. Survival, development, and fecundity of N. fallacis were similar for all relative humidity ranges tested, except at the lowest range (60–65%), in which none of the individuals survived to maturity.

Mindarus abietinus Koch causes leaf-curl and shoot-stunting of the new foliage of Fraser fir in North Carolina. Although this injury usually has a minimal impact on the trees' health and vigor, the injury can reduce the aesthetic quality and hence the marketability of Christmas trees. The overwintering egg gives rise to the fundatrix in late March. In May and June the fundatriginia and sexuparae appear. In June the sexuales are produced and by late June oviposition has occurred. The egg remains dormant until the following spring. The within-crown distribution of the various life stages is presented. Most of the injury can be minimized by maintaining vigorous growth, and timing necessary insecticide applications. Under most circumstances chemical control should only be considered during the last year or two before harvest. Dimethoate, pirimicarb, acephate, or chlorpyrifos will provide adequate control after egg hatch but before bud break.

Water potential of Fraser fir infested with the balsam woolly adelgid, Adelges piceae (Ratzeburg), and uninfested controls was evaluated using a Scholander pressure chamber. Field measurements were taken at three locations (Mt. Rogers, Va.; Roan Mountain, Tenn.; and Mt. Mitchell, N.C.) during the 1984 growing season. June measurements at Roan Mountain and Mt. Mitchell showed that infested trees were lower in water potential than uninfested controls, but there were no significant differences in midsummer at all three sites. Infested trees at all three sites showed a lower water potential when measured in September. Increment cores taken from infested trees at all three sites contained abnormal xylem (rotholz), and nearly all cores from uninfested trees at Mt. Mitchell also contained rotholz.

Thirteen acaricides were evaluated for the control of the spruce spider mite in Fraser fir Christmas tree plantations in northwest North Carolina. Dimethoate, ethion, dicofol, and carbophenothion gave effective control when applied at the same rate by both hydraulic sprayer and mist blower. Oxydemeton-methyl also demonstrated good efficacy when applied by hydraulic spray.