Plant Disease Management Handbook

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Asparagus (Asparagus officinalis) - Decline

Cause Asparagus virus I (AVI) (aphid transmitted), asparagus virus II (AVII) (pollen and seed transmitted), and tobacco streak virus (an ilarvirus) appear to be widely distributed in commercial asparagus plantings.

Cause Puccinia asparagi, an autoecious macrocyclic rust fungus that overwinters on old asparagus stems. The summer spore stage, which is the most damaging stage, is windborne and may go through several cycles in a growing season. Reduced size and storage reserves in the crowns weakens plants and reduces yields the following season.

Image related to Asparagus (Asparagus sp.)-Rust

Note the black spore masses (telia).

OSU Extension Plant Pathology

Cause Stemphylium vesicarium (teleomorph = Pleospora herbarum), a fungus that overwinters in infected debris from the previous season's crop. Small, black, spherical fruiting bodies (pseudothecia) form in late fall and winter on asparagus fern material.

Cause Fusarium oxysporum f. sp. asparagi, F. proliferatum, and F. redolens, fungi that persist in soil and can be seed-transmitted. High soil temperatures (optimum about 82°F) favor the disease, which is more severe on plants in light soils. Low soil pH, poor soil drainage, or low levels of available Mn in soil may all favor disease.

Reddish lesions can develop on stalks bases.

Phil Hamm.

Fine roots rot away while storage roots eventually collapse from rot.

Melodie Putnam

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Asparagus (Asparagus officinalis) - Fusarium Crown and Root Rot

Asparagus (Asparagus officinalis) - Purple Spot

Image related to Asparagus (Asparagus sp.)-Decline

A 12-year-old field on the verge of being removed due to decline. Weeds have moved in as asparagus plants have died off.

Photo by Dr. Lori M. Carris & Matthew Doan,1997

Decline here can be seen as Fusarium wilt in ferns (foreground) and the invasion of weeds (lightest yellow) where the asparagus has died out.

Photo by Lori M. Carris & Matthew Doan, 1997.

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Maple (Acer spp.) - Verticillium Wilt

Image related to Ash (Fraxinus spp.)-Verticillium Wilt

Defoliation may be observed without other symptoms.

Photo by Rich Regan, 2002.

Leaves may scorch before falling from the tree.

Photo by Rich Regan, 2002.

Symptoms of Verticillium wilt on white ash.

Photo by Rich Regan, 2002.

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Crabapple (Malus spp.) - Stem Rot

Cankers appear slightly sunken and darker than normal on this green ash.

Melodie Putnam, 1996.

Image related to Ash (Fraxinus spp.)-Phytophthora Canker

Note the dark canker on the side of this trunk.

Photo by Rich Regan, OSU, NWREC.

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Ash (Fraxinus spp.) - Anthracnose

The fungus Mycosphaerella fraxinicola (also known as Pseudocercosporella fraxini) was found in these leaf spots.

Oregon State University Plant Clinic image, 2020.

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Apple (Malus spp.) - Anthracnose (Bull's-eye Rot)

Image related to Ash (Fraxinus spp.)-Coin Canker

Cankers are smooth, round, brownish yellow, and range in size from 0.5 to 1.5 inches in diameter.

Linnea Skoglund, 2011.

The margins on larger cankers are distinctly reddish and have cracked margins.

OSU Plant Clinic Image, 2014.

Cause The fungus Plagiostoma fraxini (asexual: Discula fraxinea) has been identified in the Pacific Northwest. The pathogen overwinters on blighted twigs and petioles. Spore spread and infection occurs during wet weather in spring. More infections and larger symptoms can occur if wet weather persists. New infections and lesion growth are prevented when the weather turns hot and dry.

Image related to Ash (Fraxinus spp.)-Anthracnose

Note the necrotic spots on these leaves.

Jay W. Pscheidt, 2012.

Note the discrete brown or tan blotches on distorted leaves.

Photo by Neil Bell, 2004

Anthracnose may appear as individual spots or large blighted areas.

Melodie Putnam, 2008.

Necrotic leaf blight on leaflets.

Photo by Jay W. Pscheidt, 1994.