Plant Disease Management Handbook

Cause Both Phoma sp. and Phomopsis sp. have been described on vinca. The two fungi are very similar in cultural and some disease characteristics. They are favored by high soil moisture and frequent overhead irrigation.

Symptoms Shoot tips become dark brown, wilt, and die back to the soil surface. Some affected stems are nearly black.

Cultural control

Image related to Vinca spp. (Periwinkle)-Canker and Dieback
Image related to Vinca spp. (Periwinkle)-Canker and Dieback
The fungus Phoma sp. is causing stems to die down to the soil line.
Photo by Melodie Putnam, 2001.
Image related to Vinca spp. (Periwinkle)-Canker and Dieback
Stem cankers due to Phoma sp. The outer left and right stems are not affected.
Photo by Melodie Putnam, 2001.

See:

Greenhouse Plants, Ornamental - Gray Mold

Image related to Vinca spp. (Periwinkle)-Botrytis Blight
Image related to Vinca spp. (Periwinkle)-Botrytis Blight

Flowers can easily be infected. Hard to know if the fungus then moved into the vine tissue or if the tissue was already dead due to other problems and then colonized by Botrytis.

Jay W. Pscheidt, 2014.
Image related to Vinca spp. (Periwinkle)-Botrytis Blight

Infected flowers can fall onto foliage allowing the fungus to infect leaves.

Jay W. Pscheidt, 2014.

See:

Pansy (Viola spp.) - Thielaviopsis Root Rot (Black Root Rot)

Black root rot on Vina minor 'Bowles'.

OSU Plant Clinic Image, 2017.

Roots are intially brown but develop the diagnostic flat, black root lesions due to the abundant formation of chlamydospores on the root surface and in the root cortex.

OSU Plant Clinic Image, 2017.

See:

Greenhouse Plants, Ornamental - Gray Mold

Image related to Viburnum-Shoot Blight
Image related to Viburnum-Shoot Blight
Shoot blight caused by Botrytis sp.
Photo by Ralph S. Byther

See:

Tanoak (Notholithocarpus densiflorus) - Sudden Oak Death

Rhododendron - Ramorum Leaf Blight and Shoot Dieback

Ramorum shoot dieback and leaf blight on Viburnum x bodnantense ‘Dawn’.

Jennifer Parke, 2003.

Initial symptoms of ramorum leaf blight on Viburnum plicatum var. tomentosum ‘Mariesii’, showing necrotic leaf spots and shoot dieback.

Photo by Jennifer Parke, 2003.

Image related to Viburnum-Ramorum Leaf Blight and Shoot Dieback
Nursery grown Viburnum plicatum tomentosum 'Summer Snowflake'plant with dark, necrotic shoots and leaf blight.
Photo by Jennifer Parke, 2003
Image related to Viburnum-Ramorum Leaf Blight and Shoot Dieback

Dead Viburnum plicatum tomentosum 'Mariesii' plant, but also note the necrotic leaf spots on leaf tips in background.

Photo by Jennifer Parke, 2003.

Cause Powdery mildew on Viburnum spp. is caused by multiple different fungal species including Erysiphe miranda, E. vibruni, E. pseudoviburni, and E. viburniphila. Only E. viburniphila and E. vibruni have been reported in the Pacific Northwest.

Image related to Viburnum-Powdery Mildew
Image related to Viburnum-Powdery Mildew

Shaded leaves may show more powdery mildew.

Jay W. Pscheidt, 2014.
Image related to Viburnum-Powdery Mildew

Powdery mildew mycelium can be very sparse but seen with incidental light. These leaves were growing in the shade (foreground) where powdery mildew pressure is higher.

Jay W. Pscheidt, 2014.

See:

Viburnum - Bacterial Blight

Image related to Viburnum-Leaf Spots
Image related to Viburnum-Leaf Spots

Cercospora leaf spot of Viburnum.

OSU Plant Clinic Image, 2014.

Chlorosis on this viburnum due to Alfalfa mosaic virus.

Melodie Putnam, 1998.

Cause Pseudomonas syringae pv. viburni, a bacterium that can be a problem in cool, wet springs. Pseudomonas syringae pv. syringae may also occur on viburnum in the PNW. Although the bacteria survive on the outside of the plant they must get inside and multiply in the space between plant cells (apoplast) to cause disease.

2 new, deformed shoots of viburnum
2 new, deformed shoots of viburnum

Note the necrotic, deformed leaves.

Photo by Jay W. Pscheidt, 1993.

Image related to Viburnum-Bacterial Blight
Note the angular sides of many of these leaf spots.
Jay W. Pscheidt, 2006.
Image related to Viburnum-Bacterial Blight
Leaves and shoots can be affected.
Melodie Putnam, 2010.

See:

Greenhouse Plants, Ornamental - Impatiens Necrotic Spot

Symptoms Small, necrotic spots can develop on leaves, or leaves can be scorched. Plants generally look ratty and die back. Both tomato spotted wilt virus (TSWV) and impatiens necrotic spot virus (INSV) can infect verbena.

Note the necrotic spots on the leaves due to INSV.

Photo by Stacey Fischer, 1990.

This poor plant is infected with INSV.

Melodie Putnam.

See:

Greenhouse Plants, Ornamental - Powdery Mildew

The powdery mildew on this Verbena bonariensis has covered almost all the leaves and stems.

Photo by Jay W. Pscheidt, 2001.