Plant Disease Management Handbook

See:

Oak (Quercus spp.) - Mistletoe (a True Mistletoe)

Image related to Fir, Douglas and True-Dwarf Mistletoe

Dwarf mistletoe infection is becoming noticeable on these Douglas-fir branches. Note the browish male stems of the mistletoe among the green needles.

Photo by Everett Hansen, 1980.

Douglas-fir with large mistletoe brooms.

Photo by Everett Hansen, 1999.

Occasionally large brooms may form on Douglas-fir with no apparent cause.

Jay W. Pscheidt, 2020.

Not all brooms are due to dwarf mistletoe. This unknown growth occurred on Douglas-Fir in the Portland area where dwarf mistletoe is not know to occur.

OSU slide collection, 2009.

See:

Fir, Douglas and True - Hypocotyl Rot and Root Rot

Spruce (Picea spp.) - Cylindrocarpon Root Rot

Image related to Fir, Douglas and True-Damping-off

Douglas-fir seedling wilting due to infection with Pythium irregulare.

Jerry Weiland, 2012.

Douglas-fir seedling with Pythium irregulare. Note wire stem symptom near ground line and algal growth on media indicating very wet conditions.

Jerry Weiland, 2012.

Douglas-fir with Pythium irregulare (healthy plant on left, 3 diseased plants on right).

Jerry Weiland, 2012.

Cause The fungus Leptographium wageneri var. pseudotsugae in young Douglas-fir stands west of the Cascade Range that have been thinned (especially in the interior areas of southwest Oregon) and Grosmannia wageneri (formerly L. wageneri var. ponderosum) on old ponderosa pine stands east of the Cascade Range.

Image related to Fir, Douglas (Pseudotsuga menziesii)-Black-Stain Root Disease

Symptoms in xylem of four year old Douglas-fir seedling infected by the blackstain root disease fungus. Bark has been stripped to show black vascular streaking.

Jared LeBoldus, 2016.

Cause Armillaria ostoyae (may be referred to as A. solidipes in some publications) is the species associated with most conifer mortality in the Pacific Northwest, while A. mellea is considered rare.

Mycelial fans are thick, white layers of fungus that adhere to the inner root bark and/or the wood beneath the bark. This tree was found in a Laminated root rot center.

Jay W. Pscheidt, 2018.

Root rots are characterized by thin and/or chlorotic foliage and dieback of the crown.

Jay W. Pscheidt, 2018.

Notice the black rhizomorphs all over this log.

OSU Extension Plant Pathology Slide Collection.

The thick white plaques or fans of this fungus are found between the bark (phloem) and the wood (xylem).

Jay W. Pscheidt, 2018.

Go to:

Hazelnut (Corylus avellana)

Go to:

Bracken Fern (Pteridium aquilinum)

Sword Fern (Polystichum munitum)

Cause Erysiphe euonymicola (formerly Oidium euonymi-japonici), a fungus that occurs only on Euonymus japonica and is found wherever the host grows. The green cultivar Patens is very susceptible. In the past, the fungus was rarely observed on variegated cultivars but now is much more common. The fungus overwinters as mycelia and spores on infected leaves and stems. Airborne spores are spread to newly emerging leaves in the spring.

White patches generally seen first on the new growth.

Jay W. Pscheidt, 2020.

White patches to a thick felt-like mats that forms on both sides of leaves, causing some yellowing and defoliation.

Jay W. Pscheidt, 2020.

Image related to Euonymus-Powdery Mildew

Variegated types were thought to be resistant but it is found on them frequently these days.

Robin Rosetta, 2008.

Cause Rhizobium radiobacter (formerly Agrobacterium tumefaciens), a soilborne bacterium, enters Euonymus plants through wounds, either natural or caused by pruning, grafting, mechanical injury from cultivation, heaving of frozen soils, chewing insects, or the emergence of lateral roots. Pruning tools that cut through galls can become contaminated with the bacteria and spread them to cut surfaces of subsequently pruned plants.

Large, fleshy galls occur on along aerial shoots and branches.

Photo by Melodie Putnam, 2000.

Crown gall of verigated Euonymus. The normal size of this infected stem can be seen on the top left side of the gall.

Photo by Jay W. Pscheidt, 1988.

Galls are generally much larger than the parent stems.

OSU Extension Plant Pathology Slide Set, 1968.

Cause Pseudomonas syringae pv. syringae, a bacterium. Factors that favor the disease include wounds, frost damage, soil pH, poor nutrition, and infection by other pathogens. Sources of bacteria include old cankers, healthy buds, and epiphytes on leaf surfaces, weeds, grasses, and even soil. Bacteria can spread by wind, rain, insects, and infected nursery stock.

Image related to Euonymus-Bacterial Blight

Lots of necrotic spots on leaves and shoots.

Melodie Putnam, 2008.

Necrotic spots due to Pseudomonas.

Melodie Putnam, 2008.

Cause The fungus Colletotrichum gloeosporioides has been found a few times by the OSU Plant Clinic and is considered an occasional problem in BC. It is a problem on Euonymus japonica and E. fortunei including the very susceptible cultivars Canadale Gold, Emerald Gaiety, and Emerald 'n Gold. The fungus is favored by warm temperatures and long wet periods.

Leaf abscission, stem dieback and defoliation are some symptoms of anthracnose on Euonymus fortunei.

Cheryl Boyer.

Anthracnose leaf lesions on Euonymus fortunei caused by Colletotrichum gloeosporioides.

Cheryl Boyer.

Leaf lesions are characterized by small, light tan, concentric circles with orange/pink conidia eventually appearing near the outer edge of the lesion. Lesions occur on both upper and lower leaf surfaces and the necrotic centers may eventually drop out of the leaf leaving a shot-hole appearance.

Cheryl Boyer.