Infection of Douglas-fir by <i>Leptographium wageneri</i>

Hessburg, Paul F.; Hansen, E. M.

doi:10.1139/b00-097

Cited by 7 publications

(10 citation statements)

References 11 publications

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“…Such sites are reportedly used by some Rhizobium species (e.g. Gopalaswamy et al ., 2000; Vega‐Hernandez et al ., 2001) and fungi (Hessburg & Hansen, 2000; Lagopodi et al ., 2002) to invade hosts. However, these epidermal cracks may not occur naturally in the field or may be artefacts produced by growth conditions where plants are grown in artificial media such as hydroponics and agar (McCully, 2001).…”

Section: Introductionmentioning

confidence: 99%

Pathways of infection of Brassica napus roots by Leptosphaeria maculans

et al. 2007

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Summary• Infection of Brassica napus cotyledons and leaves by germinating ascospores of Leptosphaeria maculans leads to production of leaf lesions followed by stem cankers (blackleg). Leptosphaeria maculans also causes root rot but the pathway of infection has not been described.• An L. maculans isolate expressing green fluorescent protein (GFP) was applied to the petiole of B. napus plants. Hyphal growth was followed by fluorescence microscopy and by culturing of sections of plant tissue on growth media. Leptosphaeria maculans grew within stem and hypocotyl tissue during the vegetative stages of plant growth, and proliferated into the roots within xylem vessels at the onset of flowering. Hyphae grew in all tissues in the stem and hypocotyl, but were restricted mainly to xylem tissue in the root.• Leptosphaeria maculans also infected intact roots when inoculum was applied directly to them and hyphae entered at sites of lateral root emergence. Hyphal entry may occur at other sites but the mechanism is uncertain as penetration structures were not observed.• Infection of B. napus roots by L. maculans can occur via above-and belowground sources of inoculum, but the relative importance of the infection pathways under field conditions is unknown.

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Section: Introductionmentioning

confidence: 99%

Pathways of infection of Brassica napus roots by Leptosphaeria maculans

et al. 2007

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“…Experiments with inoculated Douglas-fir seedlings indicate that most minor root wounds no longer act as infection courts after 1 month, because wound closure prevents infection. The pathogen does not penetrate either intact parenchyma or callus (Hessburg and Hansen 2000).…”

Section: Black Stain Root Disease _________mentioning

confidence: 97%

“…Within infection centers, the pathogen spreads by growth in and along roots, by root grafting or root contact, and by limited hyphal growth (up to 15 cm) through the soil between roots (Cobb 1988). Infection can occur through natural openings in small roots, such as splits at root forks and sites where lateral roots emerge, or at the site of root injuries, such as caused by abrasion against rocks (Hessburg and Hansen 2000). Root lesions from Armillaria infections on adjacent trees can also allow transfer of the black stain root disease pathogen from host to host (Hessburg and Hansen 2000).…”

Section: Black Stain Root Disease _________mentioning

confidence: 99%

“…Infection can occur through natural openings in small roots, such as splits at root forks and sites where lateral roots emerge, or at the site of root injuries, such as caused by abrasion against rocks (Hessburg and Hansen 2000). Root lesions from Armillaria infections on adjacent trees can also allow transfer of the black stain root disease pathogen from host to host (Hessburg and Hansen 2000). Root damage caused by equipment can provide an abundance of infection courts.…”

Section: Black Stain Root Disease _________mentioning

confidence: 99%

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Root diseases in coniferous forests of the Inland West: potential implications of fuels treatments

Rippy¹,

Stewart²,

Zambino³

et al. 2005

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____________________________________________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.Key words: wildfire, forest planning, forest structure, mechanical treatments, prescribed fire, coniferous hosts, pathogens, disease management Foreword ______________________This document is part of the Fuels Planning: Science Synthesis and Integration Project, a pilot project initiated by the USDA Forest Service to respond to the need for tools and information useful for planning site-specific fuel (vegetation) treatment projects. The information addresses fuel and forest conditions of the dry inland forests of the Western United States: those dominated by ponderosa pine, Douglas-fir, dry grand fir/white fir, and dry lodgepole pine potential vegetation types. Information was developed primarily for application at the stand level and is intended to be useful within this forest type regardless of ownership. Portions of the information also will be directly applicable to the pinyon pine/juniper potential vegetation types. Many of the concepts and tools developed by the project may be useful for planning fuel projects in other forests types. In particular, many of the social science findings would have direct applicability to fuel planning activities for forests throughout the United States. As is the case i...

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“…; the aggressive buprestid beetle Phaenops drummondi (Kirby 1837); and the stress-responding bark beetles Dendroctonus pseudotsugae Hopkins, Scolytus unispinosus LeConte, and Pseudohylesinus nebulosus LeConte. Many of these pests are typically opportunistic and secondary (Furniss and Carolin 1977;Shaw and Kile 1991;Hessburg and Hansen 2000), indicating that post-treatment Douglas-fir mortality was related to pre-existing stress compounded by the prescribed fire and subsequent droughts. We observed that patches with mortality of large Douglas-fir resulted in larger openings with little or no tree canopy cover, and these patches were often dominated by shrubs, including blue blossom (Ceanothus thyrsiflorus Eschsch.)…”

Section: Southern Humboldtmentioning

confidence: 99%

Forest stand conditions after Phytophthora ramorum management in northern California: post-treatment observations inform future responses

Frankel

2017

For Phytophthoras

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In 2006, several isolated Phytophthora ramorum infested locations were selected just outside an 800-ha infested area in southern Humboldt County, California, for silvicultural treatments that targeted the removal and/or reduction of tanoak (Notholithocarpus densiflorus) and California bay laurel (Umbellularia californica), the main tree hosts supporting sporulation of P. ramorum. The treatments included cutting of hosts, cutting with burning, and herbicide removal. Important differences emerged between the treatment responses in shrub cover, tanoak resprouting, fuel loads, and host tree regeneration. In 2010, another isolated infestation was verified in northern Humboldt County. This infestation was 80 km away from the core infested area in southern Humboldt. Stand-level P. ramorum disease dynamic models and forest growth simulations parameterized with data collected in this northern infestation suggested that California bay laurel and tanoak thinning treatments may slow tanoak mortality, foster a greater component of mature tanoak over the next 100 years, and contribute to greater amounts of livetree carbon. Reviewing these long-running, landscape-scale P. ramorum management projects provides a platform to inform future adaptive management of P. ramorum. This paper summarizes two presentations from the Sixth

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Infection of Douglas-fir by Leptographium wageneri

Cited by 7 publications

References 11 publications

Pathways of infection of Brassica napus roots by Leptosphaeria maculans

Pathways of infection of Brassica napus roots by Leptosphaeria maculans

Root diseases in coniferous forests of the Inland West: potential implications of fuels treatments

Forest stand conditions after Phytophthora ramorum management in northern California: post-treatment observations inform future responses

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