Cause Species of Pythium, including P. ultimum (syn. Globisporangium ultimum). These are fungus-like microorganisms that survive in organic matter in soil.
Cause The fungus, Neospermospora avenae (syn. Spermospora avenae), which infects oats and the weedy winter wild oat (Avena sterilis). It was first reported on oats in western Oregon and then Washington in the 1930s. It has occurred on the east side of Washington as well as in Idaho. It is rarely a significant problem in the Pacific Northwest but is commonly a problem on oat crops in Australia and can occur in the UK as well as other regions where oats are produced.
Cause The OSU Plant Clinic has identified 4 different leaf spotting fungi from past samples of mountain ash including Cercospora, Cladosporium (leaf scorch), Gloeosporium, and Septoria spp. not including rusts.
Unidentified leaf spot on Mountain Ash.
Jay W. Pscheidt, 2022.
Cause The fungus-like organism, Phytophthora cactorum was found by the OSU Plant Clinic associated with bleeding trunk cankers. The disease and organism have also been reported from maples in home gardens in southwest Idaho. Other hosts of this organism that display bleeding cankers include beech, birch, chestnut, elm, horse chestnut, linden, oak, sweet gum, walnut, and willow. These organisms are favored by wet conditions and warm conditions.
Phytophthora cactorum was found associated with this bleeding trunk canker.
Jay W. Pscheidt, 2015.
Cause Leaf spots are common on lemon balm grown in PNW gardens but little work has been done on these problems. None have been formally reported in the PNW but the OSU Plant Clinic has found Phyllosticta and TSWV on the few samples that have been sent in. The fungi Phyllosticta decidua (now named Boeremia exigua var.
Cause Unknown. Not a common problem but found sporadically on Ennis (1990s), Jefferson (2010s) and Wepster (2020s) trees over the last few decades. Affected trees were neither considered juvenile nor mature but tended to be 5 to 10 years old on average. Affected branches do not yield any specific fungi, bacteria or viruses when sent to OSU Plant Clinic. Trees are not consistently associated with cankers, root rots or insect borers.
Jefferson hazelnut showing scattered nature of problem, branch dieback and healthy suckers.
Jay W. Pscheidt, 2016.
Dieback of Ennis hazelnut branches.
Jay W. Pscheidt, 1999.
Wepster hazelnut trees with a thinning canopy and dieback in upper branches.
Jay W. Pscheidt, 2022.
Cause Plenodomus lingam (syn. Leptosphaeria maculans, anamorph: Phoma lingam) and Plenodomus biglobosus (syn. Leptosphaeriabiglobosa) are fungi that can infect a range of cruciferous crops.