Plant Disease Management Handbook

Cause Both Phytophthora sp. and Pythium sp. have been isolated in the OSU Plant Clinic. Phytophthora cinnamomi has been reported several times and Phytophthora hydropathica has been found both in irrigation water and from root-crowns of wilting plants. Excess water is the most important factor favoring disease development.

See:

Crabapple (Malus spp.) - Stem Rot

Kalmia (Mountain Laurel) - Leaf Spots

Rhododendron - Ramorum Leaf Blight and Shoot Dieback

See:

Azalea (Rhododendron spp.) - Ovulinia Petal Blight

Azalea (Rhododendron spp.) - Botrytis Petal Blight

See:

Rhododendron - Necrotic Ringspot

See:

Rhododendron - Ramorum Leaf Blight and Shoot Dieback

See:

Seed Crop, Crucifers (Brassica, Eruca, and Raphanus spp.) - White Leaf Spot and Gray Stem

By C. M. Ocamb

See:

Seed Crop, Crucifers (Brassica, Eruca, and Raphanus spp.) - Sclerotinia Stem Rot

By C. M. Ocamb

Cause Phytophthora megasperma a fungus-like microorganism that survives as resistant spores in the soil and infects its hosts with swimming zoospores under wet conditions. All crucifer crops are susceptible, as are most cruciferous weeds.

See:

Seed Crop, Crucifers (Brassica, Eruca, and Raphanus spp.) - Downy Mildew (Staghead)

By C. M. Ocamb

Cause The fungi or fungus-like microorganisms, Pythium debaryanum, Globisporangium ultimum (formerly P. ultimum), Fusarium spp., and Rhizoctonia solani, attack young seedlings of many vegetables, including members of the genus Brassica.