Plant Disease Management Handbook

Nonpathogenic Phenomena

Image related to Nonpathogenic Phenomena
Jay W. Pscheidt, 2007.
Image related to Nonpathogenic Phenomena

In this section

Tree Decline

Image related to Tree Decline

Note the general reddening of the leaves of this maple.

Melodie Putnam.
Image related to Tree Decline

Note the general dieback of this arborvitae foliage which was later found to be due to water stress.

Melodie Putnam.
Image related to Tree Decline

Sweetgum (Liquidambar sp.) has wonderful red fall foliage but something is wrong when it shows up in late August. These trees show symptoms of tree decline.

Jay W. Pscheidt, 1995.

Image related to Tree Decline

Parasitic Plants of Oregon

Image related to Parasitic Plants of Oregon

Indian Paintbrush, Castilleja sp.

Jay W. Pscheidt.

Image related to Parasitic Plants of Oregon

Mistletoe (Phoradendron villosum) on oak in southern Oregon.

Jay W. Pscheidt, 1990's.

Image related to Parasitic Plants of Oregon

Dodder (Cuscuta sp.) found on orchard weeds in eastern Oregon.

Jay W. Pscheidt, 1990's.

Image related to Parasitic Plants of Oregon

Dodder (Cuscuta sp.) in full flower on watermelon in eastern Oregon.

Jay W. Pscheidt, 1994.

Image related to Parasitic Plants of Oregon

Dwarf Mistletoe on Ponderosa pine.

Jay W. Pscheidt, 2014.

Lower leaves on both of these Castilleja sp. have powdery mildew, likely Podosphaera fuliginea. Collected at wolf rock Oregon.  

Jay W. Pscheidt, 2020.

Image related to Parasitic Plants of Oregon

Bacteria and Other Prokaryotes

Image related to Bacteria and Other Prokaryotes

Petri plates with yellow bacterial colonies.

Jay W. Pscheidt, 2010.
Image related to Bacteria and Other Prokaryotes

In this section

Fungi

Image related to Fungi

Mummified blueberry, now a pseudosclerotia of Monilinia vaccinii-corymbosi, germinating to form  apothecia. (Evil eyes Photoshopped in for your enjoyment.)

Jay W. Pscheidt, 2013.
Image related to Fungi

In this section

Nematodes

Image related to Nematode

Ayoub, 1980.

Angular lesions are due to the foliar nematode on this Stachys sp.

OSU Plant Clinic collection, 2012.

Nematode trapping fungus.

OSU Plant Clinic, 2020.

Russ Ingham and Kathy Merrifield, 1997.

Image related to Nematode

Oregon’s Most Unwanted: Invasive Species

Image related to Oregon’s Most Unwanted: Invasive Species

Symptoms of Plum Pox Virus on peach fruit including rings and blotches of uneven color. Courtesy Ontario Ministry of Agriculture, Food and Rural Affairs. © Queen's Printer for Ontario, 2010. Reproduced with permission.

Queen's Printer for Ontario, 2010.
Image related to Oregon’s Most Unwanted: Invasive Species

In this section

Pathogens Common to Many Plants

Image related to Pathogens Common to Many Plants

Conidium of Alternaria solani that has germinated on a potato leaf surface and formed several appressoria. (Dark elongate structure is the conidium while the dark circular object is an air bubble.)

Jay W. Pscheidt, 1980's.
Image related to Pathogens Common to Many Plants

In this section

Pathogen Articles

Image related to Pathogen Articles

Plant pathogens can include fungi, bacteria, viruses, nematodes and even parasitic plants. Non-pathogenic phenomena include such things as environmental problems, nutrition excess or deficiency, and moss or lichens.

(Image shows blue stained fungal ascospores of Anisogramma anomala and rounded pollen of hazelnut.)

Stephanie Hechert, 2011.
Image related to Pathogen Articles

In this section