Note the numerous small, circular, white to yellow spots.
Photo by Debra A. Inglis.
Note the irregularly-shaped spots with an olive-black color due to sporulation.
Photo by Debra A. Inglis.
By L.J. du Toit and C.M. Ocamb
Cause Fusarium oxysporum f. sp. spinaciae, a fungus that can survive many years in soil without a spinach crop. The fungus also can colonize roots of beet and Swiss chard plants, but does not cause disease on these crops. The fungus can survive on seed and cause disease in fields previously free of spinach wilt. Warm, acidic soils favor the pathogen.
A spinach seed field with wide-spread plant die-out due to Fusarium wilt.
Photo by Cynthia M. Ocamb, 2019.
A healthy spinach plant in the foreground on the right, the brown plant in the middle that has died due to Fusarium wilt, and the plant on the left has leaves turning yellow then brown as the affects due to Fusarium wilt take hold.
Photo by Cynthia M. Ocamb, 2019.
A spinach seed plant suffering from Fusarium wilt has been split open longitudinally to show the brown-colored tissues inside the plant that are characteristic of wilt diseases in this crop.
Photo by Cynthia M. Ocamb, 2019.
By C.M. Ocamb and L.J. du Toit
Note the yellowish coloration of the upper surface of the leaves on the left. A downy growth is visible on the underside of the two leaves on the right.
Photo by Melodie Putnam, 2002
A closer view of the downy growth on the underside of a leaf.
Photo by Melodie Putnam, 2002.
Cause Pythium spp. and Rhizoctonia solani are soil-infesting microbes that can build up rapidly and attack young germinating seedlings when soil is moist.
Symptoms Stems are attacked as young plants emerge. Plants wilt, fall over, and die. Germinating seed also can be attacked, rotting plants before they reach the soil surface.
Cause Two fungi, Phakopsora pachyrhizi and P. meibomiae, cause rust on soybean, snap bean, dry bean, cowpea, and numerous other legume species. P. pachyrhizi is considered the more aggressive strain on soybean and also infects kudzu (Pueraria lobata). Disease increases on leaf surfaces during prolonged periods of wet weather and temperatures range from 59°F to 86°F.
Cause The fungus Erysiphediffusa (formerly Microsphaera diffusa) has been reported from Oregon, Washington and Idaho while Podosphaera clandestine has been reported from Washington and Idaho.
Symptoms White to gray powdery growth on the surface of leaves. Leaves may be deformed if infected when not fully expanded.
Heavy growth of the fungus can be seen in this photo.
Robin Rosetta, 2008.
Cause Many fungi are capable of causing necrotic leaf spots on snowberry. Of these, Phyllosticta symphoricarpi, Ascochyta tenerrima, Septoria symphoricarpi, and Sphaceloma symphoricarpi (anthracnose) are reported as widespread throughout Northwestern States.
Septoria leaf spot with pycnidia in the center of the necrotic area.
Jay W, Pscheidt, 2008.
Cause Puccinia antirrhini, a fungus carried in diseased cuttings or spread by wind-blown rain, splashing water or clothes. Spores can also be spread by wind over long distances. Two races of the fungus have been identified. It is not carried in seed but may contaminate seed or seed pods. Plants must be wet 6 to 8 hours for infection to occur. The disease is favored by 55°F to 70°F temperatures but inhibited by temperatures above 80°F. Earwigs eat pustules and spores from their feces are not viable.
Pale or yellow spots can be seen on the lower set of leaves.
Jay W. Pscheidt, 2020.
Pale-yellow spots on the upper leaf surface but chocolate-brown spots on the lower leaf surface.
Jay W. Pscheidt, 2020.
Upper leaf surface with yellowish spots far right and left. Lower leaf surface of 4 middle leaves showing chocolate-brown pustules - uredinia and/or telia.
Jay W. Pscheidt, 2020.
Concentric rings of chocolate-brown spores of the fungus form on stems and the undersides of leaves.
Photo by Ralph S. Byther
Cause The fungus Golovinomyces orontii (formerly Erysiphe cichoracearum) has been reported from Washington. Conidia are released in response to abrupt decreases in relative humidity. Wind blows conidia to healthy foliage where they start new mildew colonies. Too much water, such as flowing water or rain, destroys spores by causing them to burst. The fungus does not grow in a leaf but rather across the surface.
