Plant Disease Management Handbook

Cause Macrophomina phaseolina is a soilborne fungus that is favored by dry and warm soil conditions. Although the pathogen has an extensive host range, this form of the fungus is specific to strawberry. Disease development is enhanced by high temperature, soil water deficit, strawberry monoculture, and sandy soils. The fungus produces microsclerotia for long-term survival and dispersal in the soil.

Crown rot of this strawberry due to Macrophomina phaseolina.

OSU Plant Clinic image, 2015.

Roots have just about rotted away on this strawberry plant.

OSU Plant Clinic image, 2015.

Cause This is a physiological disorder. High fertility and high temperatures aggravate the disorder. Research indicates it is caused by an imbalance of calcium. Water stress followed by a period of excessive growth and dry soil conditions favors development of tip burn.

See:

Fir, Douglas and True - Stem Decays (Heart Rots)

Red Ring Rot develops bracket-like gray to brown conks with golden-brown angular pores on the underside on the stem.

OSU Plant Clinic, 2025. 

Cause The fungi Gloeosporium sp. has been found in Oregon and Colletotrichum sp. was found in Washington. These pathogens generally overwinter in leaf litter; therefore, infested debris can serve as an important source of initial inoculum. Prolonged periods of leaf wetness can also favor disease development.

Stem lesions and conidiomata of Colletotrichum sp.

Andrea R. Garfinkel, 2016.

See:

Greenhouse Plants, Ornamental - Pythium Seed Rot, Damping-off, and Root Rot

This Penstemon × mexicali ‘Carillo Purple’ had root rot due to Pythium sp.

OSU Plant Clinic image, 2014.

See:

Fire Blight of Apple and Pear

Pear (Pyrus spp.) - Fire Blight

See:

Cherry (Prunus spp.) - Prunus Necrotic Ringspot

Peach (Prunus persica) - X-Disease

Slide is labeled "Peach Calico" which has since been shown to be due to Peach latent mosaic virus but can also be confused with Peach mosaic virus.

OSU Extension Plant Pathology Slide Collection, 1991.

Slide labeled "Peach Ringspot Virus" on 'Hale' peach which we assume means Prunus necrotic ringspot virus.

OSU Extension Plant Pathology Slide Collection, circa 1950's.

Slide is labeled Peach Wart.

OSU Extension Plant Pathology Slide Collection, circa 1950's.

Old slide clearly shows rosette symptom on peach clv 'Muir' grown in West Salem, OR. Labeled "Peach Green Rosette" and speculated about it being due to a cherry virus (since cherry orchards were on either side). Not likely the peach rosette phytoplasma since trees would die quickly. Possible Peach rosette mosaic virus but slide does not indicate mosaic symptoms. 

OSU Extension Plant Pathology slide collection, circa 1950s.

See:

Boxwood (Buxus spp.) - Boxwood Blight

Cause Fusarium oxysporum f. sp. perniciosum has been diagnosed a few times in Oregon by the OSU Plant Clinic. Soilborne fungus that is difficult to control. The cultivars Tryon and Charlotte are reported to be resistant.

Symptoms Leaf wilting and defoliation along with internal black streaks in the wood and eventually tree death.

Internal black streaks in the wood.

OSU Plant Clinic, 2025.

See:

Maple (Acer spp.) - Nectria Canker