Race identification of stripe rust (Puccinia striiformis West. )
is influenced by environment, pathogen variability and host age.
Isolates of stripe rust were collected in the Pacific Northwest and
characterized on two sets of differential varieties; the "Oregon" and
the United States. Six of the seven isolates tested on the...
In vitro tests showed mycelial growth of Pyrenochaeta
terrestris was inhibited by root and bulb extracts from the pink root
resistant onion cultivar Nebuka, but not by extracts from the susceptible
Southport White Globe. The active principle was shown to be
fungistatic rather than fungicidal. It is present in both...
Root rot of ponderosa pine caused by Armillaria mellea was
studied in a pine forest that had been under management for 30 years
in Klickitat County, Washington. Information sources included
disease survey, detailed observation and description of specific
disease situations, and examination of roots in situ and removed.
Roughly circular...
In 1967, Lophodermella morbida Staley and Bynum, a recently described
hypodermataceous needle-cast fungus, became destructively
epidemic in a knobcone pine (Pinus attenuata Lemm.) plantation in
Del Norte County, California, and in several ponderosa pine (P.
ponderosa Laws.) plantations in western and southwestern Oregon.
This thesis presents information on this currently...
Self-interactions (effects of reinoculation with the same nematode)
in Meloidogyne hapla and Heterodera schachtii on Beta vulpris at
different levels of inocula with various population combinations were
studied. In M. hapla, the only significant increase of galls was
noted in treatments when 250+250 larvae were inoculated at 10-day
intervals. Longevity...
Footrot of wheat (Cercosporella herpotrichoides Fron) is a
major disease of winter wheat in certain areas of the world having a
cool, damp winter and early spring climate. In Oregon, it is an
economic problem in the higher rainfall wheat-growing areas in the
eastern portion of the state. This study...
Observations of bacterial soft rot of onions in the Lake Labish
area in the Willamette Valley of western Oregon showed that two distinct
symptom types occur during the growing season. The most
prevalent symptom type appears in infected plants as a wilting and
chlorosis of two or more lower leaves...
Cambial activity was studied in trees infested by the balsam
woolly aphid and in non-infested trees of grand and subalpine fir.
Infested and non-infested samples of grand fir were collected near
Corvallis during 1968 and 1969. Samples of subalpine fir, noninfested
and infested, were collected near Odell Lake, at approximately...
In 1967, Doi et al. proposed the hypothesis that 'yellows type
diseases' are caused by mycoplasma. Since then more than 60
yellows diseases have been associated with mycoplasma-like bodies
(MLB) (Maramorosch, 1973). The majority of these associations are
based upon electron microscopic observations of mycoplasma-like
bodies in situ. However, little...