The root insect-- black-stain root disease association in Douglas-fir : vector relationships and implications for forest management
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
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
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.
Advisor:Schowalter, Timothy D.; Berry, R. E.; Stephen, W. P.; Perry, D. A.; Tappeiner, J. C.
School:Oregon State University
School Location:USA - Oregon
Source Type:Master's Thesis
Keywords:douglas fir diseases and pests
Date of Publication:04/30/1985