Infection of Outplanted Douglas-fir Seedlings by Verticicladiella Wageneri (black Stain Root Disease) when Planted Around Infected Douglas-fir Stumps PDF Download

Author: David H. Adams
Publisher:
ISBN:
Category : Douglas fir
Languages : en
Pages : 16

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Author: Thomas C. Harrington
Publisher:
ISBN:
Category : Nature
Languages : en
Pages : 168

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Author: Eric Andrew Allen
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Category : Forest health
Languages : en
Pages : 146

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Author: Paul F. Hessburg
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Category : Conifers
Languages : en
Pages : 12

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Author:
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Category : Forest reserves
Languages : en
Pages : 280

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Author: Paul Francis Hessburg
Publisher:
ISBN:
Category : Douglas fir
Languages : en
Pages : 328

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Verticicladiella wageneri Kendr. is a vascular wilt pathogen of Douglas-fir in the Pacific Northwest, The disease is characterized by black staining of colonized sapwood; crown symptoms are those typical of a wilting syndrome. Histopathological studies revealed that the pathogen is limited to the xylem but causes vascular dysfunction in both the xylem and phloem. In xylem, hyphae grew in lumens of mature tracheids increasing resistance to the flow of xylem sap; bordered pit penetration facilitated intertracheal growth. Living host cells were never invaded by hyphae and evidence for the primary involvement of translocateabie phytotoxins was lacking. Increased vertical and circumferential extension of the fungus, systematically reduced the capacity of vascular tissue to conduct water. Phloem vascular dysfunction occurred with no evidence of mycelial invasion of phloem tissues. The appearance of engorged sieve cells and flattened albuminous cells, adjacent only to regions of heavily ramified xylem, suggested that this xylem colonization indirectly impeded centripetal transport of photosynthate through rays. Xylem pressure potential and transpiration water uptake were periodically measured on V. wageneri inoculated and control seedling groups to indicate the earliest significant consequence of vascular tissue colonization. Circumferential colonization of inoculated seedling roots consistently exceeded 90% when significant differences in pressure potential and water uptake were first apparent; radial colonization was proportionally less (35-61%). This pattern, supported by the histopathological evidence, suggested that foliage wilting was related to vascular occlusion. Root infections of dip-inoculated Douglas-fir seedlings were initiated through artificial wounds and natural openings to exposed xylem, and living bark and cambial tissues were never directly penetrated by hyphae, Root graft transmission of V. wageneri in Douglas-fir was verified from field excavations in natural infection centers. In potted seedling experiments, healthy seedlings regularly became infected whether intertree root contact was allowed or completely restricted. In growth chamber experiments, cool soil temperatures favored infection and establishment of V. wageneri in inoculated Douglas-fir seedlings; warm temperatures decreased the likelihood of infection. Vertical growth rate varied predictably with soil temperature fluctuations in the greenhouse; soil temperatures within or above the growth optimum range favored faster growth of V. wageneri in xylem. Growth rates in roots of older trees compared favorably with estimates of the annual rate of radial increase of infection centers.

Author: California State Library
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Category : California
Languages : en
Pages : 880

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Category : Jackson Demonstration State Forest (Calif.)
Languages : en
Pages : 338

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Author: Jeffrey John Witcosky
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ISBN:
Category : Douglas fir
Languages : en
Pages : 268

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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: James W. Edgren
Publisher:
ISBN:
Category : Douglas fir
Languages : en
Pages : 8

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