Plant Disease Management Handbook

Cause Phytophthora spp., fungal-like organisms that thrive in water saturated soil and/or poor drainage conditions. Several different species have been identified throughout the world on Aucuba. The organism infects at the tips, middle and junctions of lateral root branches. Entire roots become necrotic as the pathogen colonizes the tissue. Depending on the species, the pathogen may continue up into the stems causing the plant to collapse and die.

Note better condition of Aucuba plants as they are planted at increasing distances from the drain.

Jay W. Pscheidt, 2022.

Cause Leaf spots of Aucuba have been a common problem sent into the OSU Plant Clinic. A wide variety of fungi have been isolated and many have been considered secondary invaders (such as Pestalotia sp.) to abiotic issues such as sunburn. The fungi Colleotrichum gloesporeiodes and a Phomopsis sp. have been found by the OSU Plant Clinic and reported from WA.

See:

Maple (Acer spp.) - Leaf Scorch

Note: These are shade loving plants that do not tolerate full sun even for part of the day.

Leaves get a washed out chlorotic look or have marginal or tip necrosis when in full sun.

Jay W. Pscheidt, 2008.

Cause The fungus, Rhizoctonia spp., has been found on Astragalus in Oregon. Rhizoctonia spp. occurs in Oregon on other crops and may incite disease on numerous other crops including arugula, beets, snap bean, clover, peppermint, and brassicas. This fungus also causes damping-off of a wide range of plant species. It overwinters in soil as durable, long-lived structures known as sclerotia, but can also survive in association with infected plant debris.

See:

Cypress (Cupressus spp.)-Canker

Plant Viruses: Dead or Alive?

Virus particles can be rod shaped, like TMV on the left or isometric (spherical) as on the right.

Teresa Sawyer, Electron Microscope Facility. Images taken with the Titan ChemiStem made by FEI CO in Hillsboro OR.

Aphids feed on plants using a stylet that pierces plant cells. Viruses may be simply picked up in and/or on the stylet when an aphid feeds on a virus-infected plant. The virus can then be moved when the aphid feeds on a healthy plant.

Jay W. Pscheidt, 2021.

Nematodes, such as this Xiphinema spp. juvenile, can transmit plant viruses. An identifying characteristic of this plant-parasitic nematode is multiple stylets where one is lost after each stage of molt. The stylet is used to feed on plant root tissue where the nematode can acquire and transmit viruses.

Catherine Wram, 2018.

Note the irregular break in red color of these tulip flowers. This can be due to any of several viruses including Tulip breaking virus, Tulip band-breaking virus, Tulip top-breaking virus, Rembrandt tulip-breaking virus and Lily mottle virus.

Note the irregular break in red color.

Photo by Kathy Merrifield, 1991.

Note the numerous enations on the underside of this cherry leaf due to Cherry rasp leaf virus.

Jay W. Pscheidt, 1990.

Fleck is characterized by white or yellowish spots on these lily leaves which barely are noticeable in the youngest leaves but conspicuous in older ones.

Tom Allen Collection.

Blackberry Calico Virus on Marionberry. Note the striking yellow line patterns on the leaves.

Kathy Merrifield, 1991.

Mosaics are patches of dark green, light green or white on leaves of affected plants. Symptoms are not evenly distributed as each of these leaves were from the same rose plant with Rose mosaic disease.

Jay W. Pscheidt, 2012.

Leaf veins turn yellow or almost white on these honeysuckle plants with Honeysuckle yellow vein mosaic virus or Honeysuckle yellow vein virus. Not every leaf has the exact same pattern.

Jay W. Pscheidt, 2013.

Several virus symptoms can occur on the same plant. Ringspots on the left side, vein clearing in the center (yellow rather than green leave veins) and in the bottom right you can see a leaf with a line pattern (wavy or zig-zag line across the leaf blade) on this flowering cherry tree.

Jay W. Pscheidt, 2020.

Copper-based Bactericides and Fungicides

Not all copper-based pesticides are blue colored as some are red or green as well as different shades of blue.

Heather Scheck, 1990s.

Copper ions are more soluble at low pH so when copper pennies are found in acidic soils (right side of image) they may be in various stages of decay.

Jay W. Pscheidt.

A bag of hydrated lime on a bag of copper sulfate

Bordeaux contains copper sulfate and spray lime mixed just before application with water.

Jay W. Pscheidt.

There are many different copper-based pesticides and formulations.

Jay W. Pscheidt.

Copper-based pesticides may have more than one active ingredient (such as Badge) and some are registered for the home garden (such as Liqui-cop).

Jay W. Pscheidt.

Cause Wisteria vein mosaic virus has been reported from Washington and observed in Oregon. The disease has been observed in nurseries and home landscapes. As a potyvirus, an aphid is expected to be a vector of this disease. Vegetative propagation of infected plants, however, will easily spread the disease.

Healthy leaf upper left while other leaflets have mosaic, mottling and.or chlorotic spots.

Jay W. Pscheidt, 2020.

Healthy leaf on top while other leaves have various symptoms of mosaic, mottling, and/or chlorotic spots.

Jay W. Pscheidt, 2020.