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Author: Jeffrey John Witcosky Publisher: ISBN: Category : Douglas fir Languages : en Pages : 102
Book Description
The root systems of Douglas-fir trees infected with Verticicladiella wagenerii and assigned by crown color and terminal growth characteristics to several stages of decline were excavated at three widely separated sites in the Coast Range of Oregon. Data were gathered on insect species present, extent of colonization of the root system and lower stem by V. wagenerii, and the presence or absence of viable V. wagenerii inoculum, either as hyphae in wood or as conidia, within diseased trees. The weevils Steremnius carinatus and Pissodes fasciatus and the scolytid Hylastes nigrinus were commonly associated with diseased roots and root collar-lower stem portions of diseased trees. In established pockets of V. wagenerii-induced mortality, damage by S. carinatus and P. fasciatus was always noted in trees in the year of death and H. nigrinus damage occurred in 92% of these same trees. H. nigrinus and S. carinatus, associated primarily with root damage, were the first insects to invade diseased trees. Insects sequentially colonized roots of the diseased trees as each root succumbed to infection; the colonization process spanned two to four years in most cases. P. fasciatus attack was associated with tree death. V. wagenerii occurred as viable inoculum throughout the decline of host trees. Viable V. wagenerii hyphae were found in 75% of the trees recently killed by the disease. Nearly 100% of all declining trees harbored viable V. wagenerii inoculum. Trees exhibiting severe crown symptoms had nearly their entire root system colonized by the pathogen. Conidiophores of V. wagenerii were observed in galleries and pupal cells of all three beetle species. The coincidence of viable inocula and adults of these three species of root-inhabiting insects at the time of their dispersal makes H. nigrinus, P. fasciatus, and S. carinatus potential vectors of black stain root disease in Douglas-fir.
Author: Jeffrey John Witcosky Publisher: ISBN: Category : Douglas fir Languages : en Pages : 102
Book Description
The root systems of Douglas-fir trees infected with Verticicladiella wagenerii and assigned by crown color and terminal growth characteristics to several stages of decline were excavated at three widely separated sites in the Coast Range of Oregon. Data were gathered on insect species present, extent of colonization of the root system and lower stem by V. wagenerii, and the presence or absence of viable V. wagenerii inoculum, either as hyphae in wood or as conidia, within diseased trees. The weevils Steremnius carinatus and Pissodes fasciatus and the scolytid Hylastes nigrinus were commonly associated with diseased roots and root collar-lower stem portions of diseased trees. In established pockets of V. wagenerii-induced mortality, damage by S. carinatus and P. fasciatus was always noted in trees in the year of death and H. nigrinus damage occurred in 92% of these same trees. H. nigrinus and S. carinatus, associated primarily with root damage, were the first insects to invade diseased trees. Insects sequentially colonized roots of the diseased trees as each root succumbed to infection; the colonization process spanned two to four years in most cases. P. fasciatus attack was associated with tree death. V. wagenerii occurred as viable inoculum throughout the decline of host trees. Viable V. wagenerii hyphae were found in 75% of the trees recently killed by the disease. Nearly 100% of all declining trees harbored viable V. wagenerii inoculum. Trees exhibiting severe crown symptoms had nearly their entire root system colonized by the pathogen. Conidiophores of V. wagenerii were observed in galleries and pupal cells of all three beetle species. The coincidence of viable inocula and adults of these three species of root-inhabiting insects at the time of their dispersal makes H. nigrinus, P. fasciatus, and S. carinatus potential vectors of black stain root disease in Douglas-fir.
Author: Jeffrey John Witcosky Publisher: ISBN: Category : Douglas fir Languages : en Pages : 268
Book Description
Verticicladiella wageneri Kendrick is a vascular wilt pathogen of conifers, causing a black staining of colonized sapwood of roots and lower stem. In Douglas-fir, V. wageneri is intimately associated with insects. Hylastes nigrinus, Pissodes fasciatus, and Steremnuis carinatus are commonly associated with diseased hosts, carry inoculum of V. wageneri in the field, successfully transmit the pathogen to seedlings under laboratory conditions, and create suitable infection courts in susceptible hosts. Furthermore, insect-mediated transmission of V. wageneri has been documented tor the first time. Stand density management, such as precommercial thinning, results in elevated activity of H. nigrinu, P. fasciatus, and S. carinatus in disturbed stands. Insects colonize roots and the root collar region of cut trees; these hosts are susceptible to infection by V. waqeneri. Also, crop trees are wounded on the roots and root collar region by H. nigrinus for one to two years following precommercial thinning. Some of these wounds penetrate to the xylem and are, therefore, suitable infection courts for V. wageneri. Time of precommercial thinning can be manipulated to significantly reduce immigration of vectors, i.e., by thinning plantations during early summer after the peak flight of H. nigrinus. H. nigrinius and S. carinatus are attracted to alpha-pinene, a major constituent of Douglas-fir oleoresin. Forest management activities that injure hosts, and hence cause release of alpha-pinene, may attract vectors of V. wageneri. H. niqrinus and S. carinatus also are attracted to ethanol. In addition, root sections infected with V. wageneri are more attractive to H. nigrinus and S. carinatus than uninfected roots. Aspects of injury and stress to hosts leading to the release of host attractants are discussed. A crop production/pest management system structure is developed which links pest management activities for black-stain root disease prevention with normal intensive forest management. Pest management should be addressed at all stages of forest management: the harvest-establishment, annual, precommercial, and commercial phases of crop production.
Author: Publisher: ISBN: Category : Roots (Botany) Languages : en Pages : 40
Book Description
After nearly 100 years of fire exclusion, introduced pests, and selective harvesting, a change in forest composition has occurred in many Inland West forests of North America. This change in forest structure has frequently been accompanied by increases in root diseases and/or an unprecedented buildup of fuels. Consequently, many forest managers are implementing plans for fuels treatments to lower the risk of severe wildfires. Impacts on root disease should be considered before selecting appropriate fuels treatments. Complex interactions exist among conifer root diseases, fuels treatments, forest structure, species composition, stand history, and other environmental factors. As forest managers prescribe fuels treatments, their success in lowering the risk of severe wildfire will depend in part on the impacts of these treatments on root disease. Root diseases are one of many factors to be considered when developing plans for fuels treatments. Choices must be made on a site-by-site basis, with knowledge of the diseases that are present. This paper provides examples of how fuels treatments may increase or reduce specific diseases and demonstrates their importance as considerations in the fuels management planning process. Several root diseases prevalent within Inland West of North America are addressed: Armillaria root disease, annosus root disease, laminated root rot, black stain root disease, Schweinitzii root and butt rot, Tomentosus root disease, Rhizina root rot, and stringy butt rot. For each disease, general information is provided on disease identification, management options, and potential effects of fuels treatments. However, many long-term studies are needed to assess effects of specific interactions among fuels treatments, root diseases, and host trees.
Author: Jeffrey John Witcosky
Author: Jeffrey John Witcosky
Author: Jeffrey John Witcosky
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Author: Paul F. Hessburg
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Author: 
Author: Ole Terrence Helgerson
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Author: United States. Forest Service
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