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Journal Article

Balsam Woolly Adelgid (Homoptera: Adelgidae) and Spruce-Fir Decline in the Southern Appalachians: Assessing Pest Relevance in a Damaged Ecosystem

Robert G. Hollingsworth and Fred P. Hain
The Florida Entomologist
Vol. 74, No. 2 (Jun., 1991), pp. 179-187
DOI: 10.2307/3495294
Stable URL: http://www.jstor.org/stable/3495294
Page Count: 9

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Topics: Sapwood, Infestation, Trees, Heartwood, Bark, Tracheids, Compression wood, Stems, Xylem, Mortality
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Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
Balsam Woolly Adelgid (Homoptera: Adelgidae) and Spruce-Fir Decline in the Southern Appalachians: Assessing Pest Relevance in a Damaged Ecosystem
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Abstract

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. /// En investigaciones se ha demostrado que la proporción alburduramen es una medida que se relaciona con la sanidad y vigor de arboles en decadencia. Infestaciones de el adelgido algodonoso del balsamo (BWA), Adelges piceae (Ratz.), causan la formación de madera anormal y disminuyen la conducción de la savia. La infestacion de BWA también se asocia con presion potencial baja (negativa) del xylema y con el incremento del duramen. Nosotros sostenemos la hipotesis de que presiones potenciales bajas (a consecuencia de la producción anormal de madera) incrementan la tasa de cavitación (llenado de gases) de las traqueidas del albur, causando la aceleración de formación del duramen. Si esta hipotesis es correcta, el ataque del adelgido causa una perdida directa e indirecta del albur. Hay evidencia de que el adelgido algodonoso del balsamo es un factor importante para el declive de pino Fraser, Abies fraseri (Pursh) Parret, en el sur de los Apalaches. Probablemente el daño del adelgido esta interactuando con otros factores del medio ambiente, lo cual causa reducciones en un porcentaje del area de albur. Para determinar la importancia de esta plaga en el declive del árbol, se puede examinar la relación que existe entre las infestaciones de adelgidos, incremento del crecimiento y el porcentaje del area de albur.

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