Plant Disease Management Handbook

Cause A fungus, Septoria petroselini, which can be seedborne. Infected seed can have reduced germination and emergence. The disease is wide spread on parsley. Avoid direct skin contact with infected plants because infected plants produce high levels of photo-carcinogenic compounds, which can result in rashes and blisters. Once this fungus is introduced to a field, it survives on non-decomposed plant debris and produces conidia under a wide temperature range (50°F to 86°F).

A parsley seed crop plant showing symptoms of Septoria leaf spot. Note the small, brown-colored lesions on leaves and petiole on the left side of the plant. Photo by Cynthia M. Ocamb, 2013.

A parsley seed crop plant showing symptoms of Septoria leaf spot.  Note the small, brown-colored lesions on leaves and petiole on the left side of the plant.

Photo by Cynthia M. Ocamb, 2013.

Leaves detached from an infected parsley plant showing characteristic brown spots on leaf and petiole tissues caused by Septoria petroselini. Photo by Cynthia M. Ocamb, 2013.

Leaves detached from an infected parsley plant showing characteristic brown spots on leaf and petiole tissues caused by Septoria petroselini.  

Photo by Cynthia M. Ocamb, 2013.

Cause The fungus, Mycocentrospora sp., has been associated with this disease on parsley in the Willamette Valley of Oregon. The fungus usually is a problem on carrot but has a wide host range of weed species. It is favored by cool soils.

Symptoms A red discoloration and lesions on roots; and lesions on petioles.

Cultural control

Cause Globisporangium paroecandrum (formerly Pythium paroecandrum), G. mastophorum (formerly P. mastophorum), and possibly other Pythium or Globisporangium spp. as well as the fungi Pythium spp., Rhizoctonia solani, and Fusarium spp.

Cause The bacterium, Pseudomonas syringae pv. coriandricola, is common; Xanthomonas campestris pv. coriandri and X. hortorum pv. carotae also have been reported. Although Pseudomonas sp. has been severe on cilantro in the Willamette Valley of Oregon, the problem occurs much less on parsley.

See:

Orchid - Bacterial Brown Spot

Note: There are many fungal and bacterial leaf spots of orchid but samples sent to the OSU Plant Clinic have mostly had abiotic brown leaf spots.

Epiphyllum sp. (orchid cactus) with oedema - an abiotic problem where subepidermal cells expand and protrude through the leaf surface.

OSU Plant Clinic image, 2010.

See:

Walnut (Juglans spp.) - Downy Leaf Spot

Cause Microstroma album a fungus that is reported to be common in Washington on Oregon oak (Q. garryana).

See:

Fir, Douglas and True - Stem Decays (Heart Rots)

See:

Begonia - Nematode, Foliar

Cause Two types of wood decay occur in living trees: white rots and brown rots. The more common fungal white rots in hemlock are caused by Ganoderma applanatus (white mottled rot), Ganoderma oregonense (spongy white rot), Phellinus nigrolimitatus (white pocket rot), and Porodaedalea pini (red ring rot).

Ganoderma sp. conk sent in for identification.

OSU Plant Clinic, 2023.

See:

Fir, True (Abies spp.) - Drought Injury