Plant Disease Management Handbook

Cause Several fungal leaf spots have been reported from the Pacific Northwest including Ramularia agrestis, R. lactea, and Cercospora violae. Other fungi such as Alternaria sp. and Colletotrichum sp. (anthracnose) are also common leaf spot problems. Leaf spots are favored by warm, humid conditions especially later in the growing season during fall.

See:

Greenhouse Plants, Ornamental - Gray Mold

Cause Two fungal-like organisms are reported to cause downy mildew on pansy: Plasmopara megasperma (formerly Bremiella megasperma) common in North America and Peronospora violae common in Europe and Asia. The disease has not been reported in the Pacific Northwest but has been observed in both Oregon and Washington. Wet, humid environments favor disease development.

See:

Pansy (Viola spp.) - Root and Crown Rot

See:

Greenhouse Plants, Ornamental - Gray Mold

See:

Honey Locust (Gleditsia spp.) - Canker

Notes Necrotic light brown cankers occur at nodes on affected stems. Older cankers are elliptical with a raised margin of callus. Wood underneath canker is discolored brown. Ariel hyphae may occur when incubated under moist conditions.

Cause Volutella pachysandrae and Coccinonectria pachysandricola (formerly Volutella pachysandricola), fungi. Much more severe on stressed plants such as those growing in full sun, wounded or weakened by scale insects or winter injury. Infection of wounds occurred for several days after the wounding event early in the growing season. Wounds occurring in the summer are much more resistant to infection.

By C. M. Ocamb and D.A. Johnson

See:

Peppermint (Mentha spp.) - Nematode, Root-lesion

Cause Several fungi that live in soil. Stolon decay is associated with Fusarium solani. Stem and stolon canker are caused by Rhizoctonia solani.

Symptoms Roots, runners, and rhizomes have brown or black progressively rotting areas. Stands may be greatly reduced, frequently in spots.

Cultural control

Cause The Impatiens necrotic spot virus (INSV) and the Tomato spotted wilt virus (TSWV) infect many economically important plants, including both dicots and monocots, and have been found in mint.