Spruce with a crown rot due to both Fusarium sp. and Pythium sp.
OSU Plant Clinic, 2020.
Cause Cytospora kunzei (sexual: Valsa kunzei), a fungus that has not been reported in the Pacific Northwest but has been found by the OSU Plant Clinic. The disease is more common in the Northeastern United States. Rain splashes spores to wounded branches. The fungus infects through wounded tissue. Other species infect pine, Douglas-fir, and true firs. They also infect trees weakened by drought, fire, insects, and other diseases, most importantly dwarf mistletoe.
Branches near the ground turn brown and die and over time, more branches continue to die slowly up the tree.
OSU Botany and Plant Pathology slide collection, 1974.
Cankers can occur on trunks as well as branches. This one occurred at a wound site.
OSU Botany and Plant Pathology slide collection, 1974.
White patches of pitch or resin may appear along the bark of dead or dying branches or trunks.
OSU Botany and Plant Pathology slide collection, 1973.
Small black fruiting bodies (pycnidia) of the fungus may be seen in the cankered area.
OSU Botany and Plant Pathology slide collection, 1974.
Cause A physiological disorder that affects the uppermost bud(s) on the terminal shoot (leader) of Colorado blue spruce (Picea pungens). Possibly caused by either a calcium deficiency or by high temperatures the previous growing season. Genetics likely play a role in tree susceptibility.
Note the dry, dark, dead terminal buds at center of picture.
Cause Several fungi have been reported on spirea but only Podosphaera clandestina, P. tridactyla, P. minor var. longissima and P. spiraeae have been reported from the PNW. Podosphaera clandestina is also found on stone fruit trees such as cherry and peach.
Powdery mildew on shoots of Japanese Spiraea (Spiraea japonica 'Crispa').
Jay W. Pscheidt, 2021.
Flag shoots from infections the previous year are easy to find after bud break.
Jay W. Pscheidt, 2018.
Flag shoots have conidia ready to go when they emerge.
Jay W. Pscheidt, 2018.
Cause Beet western yellows virus, an increasingly significant pathogen in western Oregon. The principal vector is the green peach aphid, Myzus persicae; other aphid vectors are likely. After acquiring the virus from infected plants, aphids may have lifelong ability to transmit it. An enormous number of crop and weed species are susceptible to this virus and act as natural inoculum reservoirs.
Cause Albugo occidentalis, a fungus that is not uncommon on spinach but usually of minor importance. It also infects weedy species of Chenopodium. Warm days followed by cool, dew-forming nights favor disease.
Symptoms White pustules will develop on the lower, sometimes upper surface of infected leaves as well as on petioles, and the upper leaf surface will be yellowish.
