Plant Disease Management Handbook

Cause Spiroplasma citri, which is spread by leafhoppers, has been found in industrial hemp in Oregon and Washington in disease surveys conducted by OSU in 2021 and 2022. This pathogen also occurs in carrots in Washington as well as in brassicas, tree fruits, and ornamental flowering plants including periwinkle (Catharanthus roseus).

Cause Several different fungal cankers on hawthorn have been sent into the OSU Plant Disease Clinic where the diagnoses have included Cytospora spp., Phoma sp., Phomopsis sp., Sphaeropsis sp., and the oomycete Phytophthora syringae. Cytospora canker was diagnosed most often and this fungus is a vigorous wound invader (including wounds from sunscald and winter injury).

Cause The fungi or fungus-like microorganisms inlcuding Pythium spp., Fusarium spp., and Rhizoctonia solani can attack young seedlings of many vegetables crops. Seedlings are susceptible to disease before or after emerging from soil. If seedlings are affected before emerging, it presents as poor germination.

See

Onion (Allium cepa) - Fusarium Basal Rot

See

Onion (Allium cepa) - Fusarium Basal Rot

Cause A localized calcium deficiency due to any soil or growing condition that affects calcium uptake. This physiological problem is common, especially in home gardens and can typically affect tomato, peppers, eggplant, watermelon, pumpkin, and squash. Drought, salinity and high temperatures have been found to promote blossom-end rot. If too little calcium is in the soil or if the soil is high in salts, calcium uptake will be impeded, especially under periods of sudden drought stress.

Cause Alternaria petroselini and possibly other species have been reported on coriander in Florida. Alternaria species can be seedborne. Once this fungus is introduced to a field, it survives on non-decomposed plant debris. Spread occurs with wind, water (wind-driven rain, dew drips, irrigation), and by mechanical means (tools or workers).

Cause A fungus of undetermined identity has been observed inciting powdery mildew on comfrey (Symphytum officinale) in Oregon. The fungus Golovinomyces cynoglossi (syn. Erysiphe cynoglossi) has been reported on Symphytum asperum, S. bulbosum, S. caucasicum, S.

Cause A fungus, Verticillium dahliae, which lives in soil and in diseased plants. It is soilborne and once established in soil is almost impossible to eradicate due to microsclerotia, which germinate and infect roots. The fungus grows throughout the vascular system and up into mint stems. After diseased plant parts die, microsclerotia form and remain several years in soil. The pathogen is spread with infected rhizomes used for planting and in contaminated surface irrigation water.

See:

Peach (Prunus persica) - Cytospora Canker

Grape (Vitis spp.) - Eutypa Dieback