Key Herbaceous Plants and Key Pathogens/Diseases

Selecting annuals and perennials for placement in the landscape as well as monitoring them for diseases and planning appropriate disease management strategies can be simplified if the key plants are known and if the key pathogens on those plants can be identified.  KEY PLANTS are ones that frequently have diseases and should be monitored on a regular basis.  In some locations, key plants should not be used if the amount of maintenance work required for the site looks well at all times must be minimized.  KEY PATHOGENS/DISEASES (in bold) are those that frequently occur on the plants.  The other pathogens listed sometimes occur.  If conditions at the planting site tend to favor the key diseases, the key plant should not be established there.

Begonia

Botrytis, Powdery mildew, Pythium, Impatiens necrotic spot virus, foliar nematode

Centaurea (cornflower)

Aster yellows, Crown and stem rot, Downy mildew, Powdery mildew, Rust, White rust

Chrysanthemum

Bacterial leaf spot, Botrytis flower blight, Fungal leaf spot, Powdery mildew, Pythium root rot

Clematis

Leaf spot, Powdery mildew, Root rot, Rust, Wilt, Tomato ringspot virus

Convallaria (Lily of the Valley)

Leaf spots, Foliar nematode, Rust, Southern blight

Echinacea (coneflower)

Aster yellows, Bacterial leaf spot, Botrytis stem rot, Cercospora leaf spot, Foliar nematode, Fungal leaf spot (Cercospora, Septoria), Leaf mottling (viruses), Septoria leaf spot, White smut

Geranium (Geranium and Pelargonium)

Alternaria leaf spot, Bacterial blight, Botrytis blight, Edema, Fasciation, Pythium root rot, Rust, Viruses

Hemerocallis (daylily)

Leaf spot (Colletotrichum), Leaf streak or red leaf streak (Aureobasidium), Rhizoctonia crown rot, Rust

Hollyhock (Alcea)

Anthracnose, Crown rot (Phytophthora)

Hosta

Anthracnose, Bacterial soft rot, Foliar nematode, Fusarium root and crown rot, Hosta virus X, Petiole rot

Hydrangea

Botrytis blight, Cercospora leaf spot, Powdery mildew, Virescence (phytoplasma), Viruses

Iris

Bacterial leaf blight, Bulb nematode, Crown rot, Fungal leaf spot,Ink spot, Rhixome rot, Soft rot, Viruses

Monarda (bee-balm)

Fungal leaf spots, Powdery mildew, Stem rot, Viruses

Pansy and other Viola

Anthracnose, Cercosopra leaf spot, Fusarium wilt, Rust, Pythium root rot, Scab, Thieloviopsis root rot

Peony
Bacterial blight, Botrytis blight, Crown gall, Leaf blotch or measles, Powdery mildew, Root rot, Stem rot, Verticillium wilt, Viruses

Phlox

Aster yellows, Botrytis blight, Charcoal rot, Crown gall, Cowny mildew, Foliar nematode, Root rot, Rust, Viruses, Wilt

Rudbeckia

Aster yellows, Bacterial leaf spot, Downy mildew, Fungal leaf spots, Powdery mildew, Rust, Stem rot, Verticillium wilt, Viruses

Sedum

Anthracnose, Bacterial soft rot, Fungal leaf spots, Gray mold, Powdery mildew, Root rot, Rust, Stem rot (Colletotrichum), Viruses

Tulip

Basal rot, Fire (Botrytis), Pythium root rot, Stem and bulb nematode, Viruses

Verbena

Botrytis blight, Powdery mildew, Pythium root rot

Yucca

Bacterial soft spot, Crown rot, Fungal leaf spots, Rust

Zinnia

Aster yellows, Alternaria leaf spot, Bacterial leaf spot, Powdery mildew

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Issued in furtherance of Cooperative Extension work, Acts of Congress, May 8 and June 30, 1914, in cooperation with the U. S. Department of Penn State College of Agricultural Sciences research and extension programs are funded in part by Pennsylvania counties, the Commonwealth of Pennsylvania, and the U.S. Department of Agriculture.

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