Key Herbaceous Plants and Key Pathogens/Diseases

Selecting annuals and perennials for placement in the landscape can be simplified if the key pathogens on those plants can be identified.
Key Herbaceous Plants and Key Pathogens/Diseases - Articles

Updated: February 10, 2012

Key Herbaceous Plants and Key Pathogens/Diseases

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

Notice

The user of this information assumes all risks for personal injury or property damage.

Prepared by Gary W. Moorman, Professor of Plant Pathology