Plant Disease Management Handbook

A disease symptom characterized by short, bunchy growth habit due to shortened internodes and no comparable reduction in leaf size.

a serological test in which the sensitivity of the reaction is increased by attaching an enzyme that produces a colored product to one of the reactants.

See:

Seed Crop, Crucifers (Brassica, Eruca, and Raphanus spp.) - Clubroot

By C. M. Ocamb

A couple of red radish plants showing clubbing on the main root due to clubroot. Photo by Cynthia M. Ocamb, 2012.
A couple of red radish plants showing clubbing on the main root due to clubroot. Photo by Cynthia M. Ocamb, 2012.

A couple of red radish plants showing clubbing on the main root due to clubroot.

Photo by Cynthia M. Ocamb, 2012.

Air Pollution (Ozone)

Smoke can be seen during the Columbia gorge fire of 2017. Particulates in smoke are not harmful to plants as they are to humans.

Jay W. Pscheidt, 2017.

Ozone damage to Jeffery pine (Pinus jeffreyi) shows here as small chlorotic flecks on the needles.

David Shaw, 2012.

Chlorotic spots on onion leaves due to ozone damage.

OSU Plant Pathology slide collection.

The leaf damage is unknown but ozone is suspected due to the distribution of symptoms on plants and leaves. Note the damage is worse on the upper leaf surface and between veins.  

OSU Plant Clinic image, 2012.

close up of grape leaf

Unknonw grape cultivar with angular dark spots on the top side of older leaves due to ozone. Viognier grape is sensative to ozone.

2021.

Sarcococca spp. experienced significant green leaf drop over a few days after the heavy smoke event of 2020.

OSU Plant Clinic, 2020.

Cause Sphaerulina taxi, a fungus that has been reported from all states and considered common in Washington. A problem when yew is used as a hedge.

Symptoms The needles of the current season are killed. Infected needles become light green and finally grayish or reddish brown. The upper surface of an infected needle is covered with minute black fruiting bodies (perithecia) of the fungus. The infected needles are cast.

Cause Two types of wood decay occur in living trees: white rots and brown rots. White rots appear to be more common in willow and are caused by Daedalea confragosa (soft white rot), Phellinus igniarus (white trunk rot) and Polyporus squamosus (white mottled rot).

A species of Gymnopilus fruiting on Salix scouleriana.

Jay W. Pscheidt, 2021.

A species of Gymnopilus fruiting on Salix hookeriana.

Jay W. Pscheidt, 2021.

A Ganoderma applanatum conk from a willow which indicates the presence of a white rot in the tree.

OSU Plant Clinic image, 2015.

See:

Cherry (Prunus spp.) - Silver Leaf

See:

Willow (Salix spp.) - Marssonina Leaf and Twig Spot

Willow (Salix spp.) - Rust

Black, tar-like thickened spots are produced on the upper leaf surfaces which is smooth and shiny early in the season, but becomes dull black and ridged in the fall.

OSU Plant Clinic image, 2019.

See:

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

By C. M. Ocamb

Cause The fungus, Phoma destructiva var. destructiva, can infect tomato and peppers and survives in soil or infected plant debris. This fungus can be seedborne in paprika and perhaps other crops in the family, Solanaceae. Plant injury, including by insects, enhances infection.