Search

Sassafras albidum (Sassafras) is an ecologically important tree species that is widely distributed throughout the eastern United States. Sassafras is presently threatened by Raffaelea lauricola, a fungus vectored by Xyleborus glabratus (Coleoptera: Curculionidae: Scolytinae; Redbay Ambrosia Beetle), which causes a lethal vascular wilt known as laurel wilt disease (LWD). This study summarizes the status of Sassafras across the entire eastern United States and in areas with LWD in particular, so that LWD-induced changes in the Sassafras resource may be properly understood. Inventory data collected by the Forest Inventory and Analysis (FIA) Program of the US Department of Agriculture Forest Service indicated that as of 2013-2014 there were 1.9 billion live Sassafras trees and saplings across 28 states, 53 ecoregion sections, and 69 forest types in the eastern United States. Only 1.7% of Sassafras trees ≥2.5 cm diameter at breast height occurred in counties with LWD; an additional 2.8% occurred in neighboring counties. To date, LWD has not reached the heart of the Sassafras range, yet discontinuous jumps of the disease beyond its advancing front suggest that future introductions may be possible. Landowners and forest managers within the range of Sassafras should be diligent to watch for LWD symptoms and consider the changes that may occur in their forests if the disease becomes established. [ABSTRACT FROM AUTHOR]

The laurel wilt disease fungus, Raffaelea lauricola, is killing redbay trees, spreading rapidly in the U.S. southeastern coastal plain forest, and posing a serious threat to the avocado industry in Florida. A molecular tool is urgently required to facilitate detection of this pathogen. The 5' region of the large ribosomal RNA (28S) gene is highly variable among Raffaelea spp. and ideal for this purpose but amplification of this sequence from R. lauricola has been difficult. Different amplification conditions were tested and a high-fidelity polymerase chain reaction (PCR) procedure utilizing a dNTP mix containing 7-deaza-dGTP was found to reliably amplify 28S sequences from R. lauricola. Sequencing the amplified products or cloned inserts also turned out to be difficult and required using a custom-blended sequencing mix containing 1 M betaine, 5% dimethyl sulfoxide, and dGTP-BigDye v3.1. Three GC-rich stem and loop or cruciform secondary structures were discovered, which may have interfered with amplification. This improved protocol made it possible to partially characterize the internal transcribed spacers sequence from R. lauricola, which also has interfering secondary structures. A TaqMan real-time PCR assay was designed using the species-specific 28S sequences and this allowed detection of R. lauricola from wood tissues or cultures. Wood tissues from symptomatic redbay, avocado, and sassafras trees in Florida were screened using this TaqMan assay and several were found to test positive for R. lauricola. Results were further confirmed by performing Koch's postulates for avocado specimens collected from commercial grooves. [ABSTRACT FROM AUTHOR]

Syphilis and its rapid blazing spread through the Old World in the late 15th century is controversial, riddled with claims and counterclaims of how, when, and where it originated. Three theories of thought have been proffered and all have enough convincing evidence not to be discarded. The Columbian Theory has gained the most credible following theme of its origin, and places the sexually transmitted "Treponemia pallidum", the spirochete that causes venereal syphilis with the Arwak Indians of Espanola. It was reported in the Relation of Fray Ramon Concerning the Antiquities of the Indians, that "they had shared their hands with the illness as far back as their memory would go" (Crosby, 2003, p. 122-140). The Italian physicians Niccolo Leoniceno and Niccolo Massa were the defenders of this theory (Cambridge 1998, p. 154). [ABSTRACT FROM AUTHOR]

The exotic redbay ambrosia beetle, Xyleborus glabratus Eichhoff (Coleoptera: Curculionidae: Scolytinae), and its fungal symbiont Raffaellea lauricola Harrington, Fraedrich, and Aghayeva are responsible for widespread redbay, Persea borbonia (L.) Spreng., mortality in the southern United States. Effective traps and lures are needed to monitor spread of the beetle and for early detection at ports-of-entry, so we conducted a series of experiments to find the best trap design, color, lure, and trap position for detection of X. giabratus. The best trap and lure combination was then tested at seven sites varying in beetle abundance and at one site throughout the year to see how season and beetle population affected performance. Manuka oil proved to be the most effective lure tested, particularly when considering cost and availability. Traps baited with manuka oil lures releasing 5 mg/d caught as many beetles as those baited with lures releasing 200 mg/d. Distributing manuka oil lures from the top to the bottom of eight-unit funnel traps resulted in similar numbers of X. glabratus as a single lure in the middle. Trap color had little effect on captures in sticky traps or cross-vane traps. Funnel traps caught twice as many beetles as cross-vane traps and three times as many as sticky traps but mean catch per trap was not significantly different. When comparing height, traps 1.5 m above the ground captured 85% of the beetles collected but a few were caught at each height up to 15 m. Funnel trap captures exhibited a strong linear relationship r2 = 0.79) with X. glabratus attack density and they performed well throughout the year. Catching beetles at low densities is important to port of entry monitoring programs where early detection of infestations is essential. Our trials show that multiple funnel traps baited with a single manuka oil lure were effective for capturing X. glabratus even when no infested trees were visible in the area. [ABSTRACT FROM AUTHOR]

Managers increasingly use prescribed fire in oak forests to decrease fire-sensitive species, increase understory light, and improve oak (Quercus spp.) regeneration. To better understand woody seedling response to burning, single and repeated (3×) prescribed fires were implemented over 6 years (2002–2007) in eastern Kentucky, and leaf traits of red (Erythrobalanus spp.) and white oaks (Leucobalanus spp.) were compared with competitors red maple (Acer rubrum L.) and sassafras (Sassafras albidum (Nutt.) Nees). Burned seedlings had higher total leaf area (TLA) because of two to three times higher TLA of sassafras. Leaf mass per area (LMA) and leaf N content per area (Narea) increased postfire but were independent of seedling identity. Canopy openness during 2006, which was lower on unburned sites (4%–8%) compared with those burned 1× (4%–16%) and 3× (7%–33%), was positively correlated with sassafras TLA, oak and sassafras Narea, and LMA of all seedling groups the subsequent year. In 2007, TLA, LMA, and Narea were positively correlated with basal diameter of all groups but most significantly for sassafras and red maple. These findings indicate that low-intensity, early growing season prescribed fire can alter seedling leaf characteristics, but not in a manner that enhances oak seedling leaf traits relative to their competitors red maple and sassafras. Les aménagistes utilisent de plus en plus le brûlage dirigé dans les forêts de chênes pour éliminer les espèces sensibles au feu, augmenter la lumière en sous-étage et améliorer la régénération du chêne (Quercus spp.). Pour mieux comprendre la réaction des semis ligneux au brûlage, des brûlages uniques et répétés (3×) ont été effectués sur une période de 6 ans (2002–2007) dans l’est du Kentucky et les caractères des feuilles des chênes rouges (Erythrobalanus spp.) et blancs (Leucobalanus spp.) ont été comparés à ceux des espèces compétitrices : l’érable rouge (Acer rubrum L.) et le sassafras officinal (Sassafras albidum (Nutt.) Nees). Les semis brûlés avaient une surface foliaire totale (SFT) plus élevée à cause de la SFT du sassafras qui est 2–3× plus élevée. La masse foliaire spécifique (MFS) et la teneur en N foliaire par unité de surface (Nsurf.) ont augmenté après le passage du feu peu importe l’espèce de semis. L’ouverture de la canopée en 2006, qui était plus faible dans les stations non brûlées (4 % – 8 %), comparativement à celle des stations brûlées 1× (4 % – 16 %) et 3× (7 % – 33 %), était positivement corrélée avec la SFT du sassafras, la teneur en Nsurf. du chêne et du sassafras ainsi qu’avec la MFS de tous les groupes de semis l’année suivante. En 2007, la SFT, la MFS et la teneur en N surf. étaient positivement corrélées avec le diamètre basal de tous les groupes, mais la corrélation était la plus significative dans le cas du sassafras et de l’érable rouge. Ces résultats indiquent qu’un brûlage dirigé de faible intensité effectué au début de la saison de croissance peut modifier les caractéristiques des feuilles, mais pas de façon à améliorer les caractères des feuilles des semis de chêne relativement aux espèces compétitrices, c’est-à-dire l’érable rouge et le sassafras. [ABSTRACT FROM AUTHOR]

Abstract: Studies within and outside the U.S. indicate recurring oak (Quercus spp.) regeneration problems. In deciduous forests of the eastern U.S., a prevailing explanation for this trend is fire suppression leading to high competitor abundance and low understory light. In response, prescribed fire is increasingly used as a management tool to remedy these conditions and encourage future oak establishment and growth. Within eastern Kentucky, we implemented single and repeated (3×) prescribed fires over a 6-yr period (2002–2007). Pre- and post-burn, we quantified canopy cover and oak seedling survival and growth compared to other woody seedlings deemed potential competitors, primarily red maple (Acer rubrum L.) and sassafras (Sassafras albidum (Nutt.) Nees.). Burning temporarily decreased canopy cover 3–10%, but cover rebounded the subsequent growing season. Repeated burning ultimately produced canopy cover about 6% lower than sites unburned and burned once, suggesting a cumulative effect on understory light. Red maple exhibited low survival (∼40%) following single and repeated burns, but growth remained similar to unburned seedlings. Burning had little impact on sassafras survival and led to total height and basal diameters 2× greater than unburned seedlings. A single burn had no impact on red oak (Erythrobalanus spp.) survival and increased height and basal diameters 25–30%, but this positive growth response was driven by seedlings on several plots which experienced high burn temperatures and consequently high overstory mortality. White oaks (Leucobalanus spp.), however, exhibited twice as high mortality compared to those unburned, with no change in growth parameters. Repeated burning negatively impacted survival and growth of both oak groups compared to unburned seedlings. With both burn regimes, oaks with smaller pre-burn basal diameters exhibited the lowest post-burn survival. Thus, despite the ability of prescribed burns to temporarily increase understory light and reduce red maple survival, neither single or repeated burns placed oaks in an improved competitive position. These findings result from a combination of highly variable yet interdependent factors including the (1) life history traits of oaks compared to their co-occurring competitors, (2) pre-burn stature of pre-existing oak seedlings, and (3) variability in fire temperature and effects on understory light. [Copyright &y& Elsevier]

The non-native redbay ambrosia beetle, Xyleborus glabratus Eichhoff (Coleoptera: Curculionidae: Scolytinae), has recently emerged as a significant pest of southeastern U.S. coastal forests. Specifically, a fungal symbiont (Raffaelea sp.) of X. glabratus has caused mortality of redbay (Persea borbonia) and sassafras (Sassafras albidum) trees in the region; several other Lauraceae species also seem susceptible. Although the range of X. glabratus continues to expand rapidly, little is known about the species' biology and behavior. In turn, there has been no broad-scale assessment of the threat it poses to eastern U.S. forests. To provide a basic information framework, we performed analyses exploiting relevant spatio-temporal data available for X. glabratus. First, we mapped the densities of redbay and sassafras from forest inventory data. Second, we used climate matching to delineate potential geographic limits for X. glabratus. Third, we used county infestation data to estimate the rate of spread and modeled spread through time, incorporating host density as a weighting factor. Our results suggest that (1) key areas with high concentrations of redbay have yet to be invaded, but some are immediately threatened; (2) climatic conditions may serve to constrain X. glabratus to the southeastern U.S. coastal region; and (3) if unchecked, X. glabratus may spread throughout the range of redbay in <40 yr. Disruption of anthropogenic, long-distance dispersal could reduce the likelihood of this outcome. [ABSTRACT FROM AUTHOR]