Plant Health Problems:

See Perennials for a detailed discussion of problems that may occur and are common to most herbaceous ornamentals.

Diseases caused by Fungi:

Basal or root rot, Rhizoctonia solani.
Roots and basal stems are rotted, black or brown and collapsed. Sunken lesions may occur at the soil line.

Control with fungicides is not reliably effective and may be prohibitively expensive, so removal of infected plants is important.

Downy mildew, Phytophthora.
This pathogen typically causes leaf spots with downy white or gray patches under the leaves. The downy growth results from the production of spores called sporangia which are wind-dispersed between plants. Disease is usually favored by cool wet weather.

Control may include cultural means of reducing humidity and leaf wetness. Control may also be achieved with the use of fungicides applied as soon as symptoms are visible. Among the compounds registered for use in Connecticut is mancozeb. Consult the label for dosage rates, safety precautions, and directions for use.

Gray mold, flower and leaf blight, Botrytis cinerea.
This fungus occurs everywhere and commonly infects senescing or damaged plant parts such as old flowers, causing a fuzzy gray mold. Spores are produced which are easily blown around. From these tissues the fungus moves into healthy stems and leaves, causing a damaging blight. Disease is favored by cool wet conditions and the presence of overripe fruit or old flower petals.

Sanitation is the most important means of control. Remove dead flowers before gray mold develops. If disease has moved into leaf or stem parts, control may also be achieved with the use of fungicides applied as soon as symptoms are visible. Among the compounds registered for use in Connecticut is thiophanate-methyl. Consult the label for dosage rates and safety precautions.

Insect Problems:
See Perennials.