Cause The fungus, Blumeria graminis (syn. = Erysiphe graminis). Powdery mildew survives as either chasmothecia or as mycelium. Asexual (conidia) or sexual spores (ascospores formed in the chasmothecia) produced in the spring cause new infections on susceptible hosts. As colonies develop, more conidia are produced and disseminate. The powdery mildew colonies may eventually become spotted with tiny black dots, which are the chasmothecia.
Note the yellow lesions on the leaves.
Photo part of OSU Extension Plant Pathology Slide Collection, 1974.
Heavily infected leaves soon yellow, brown, and die.
Table "Plant resistance to root lesion nematodes, Pratylenchus neglectus and P. thornei, in the Pacific Northwest"
Cause The root-knot nematode, Meloidogyne naasi, lives on roots of barley, wheat, other cereals, and grasses, primarily in heavy soils. Populations of infective juveniles are large only in spring. Spring-planted varieties are more damaged than winter varieties because the latter are larger when attacked. The disease is a problem in western Oregon. The Columbia root-knot nematode (M.
