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:

Leaf spots, Cercospora, or Phyllosticta spp.
Leaf spots are very common, typically sharply delimited necrotic areas on plant leaves caused by a wide variety of pathogenic species. Leaf spots usually are favored by wet conditions and may become important if a large number of lesions are present or if they start to coalesce.

Under those conditions, 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 are thiophanate-methyl and sulfur. Consult the label for dosage rates and safety precautions.

Smut, Entyloma spp.
Smuts are diseases caused by Basidiomycetes. While most smut diseases attack the reproductive parts of plants such as flowers, replacing them with a sooty black mass of fungal spores, smut diseases of perennials often result in light spots on leaves and are called white smuts.

This disease is not typically serious, and usually can be controlled removal of infected plant debris.

Diseases caused by Phytoplasmas:

Aster yellows, phytoplasma.
The pathogen is a prokaryotic organism without cell walls. It infects the phloem of susceptible plants and causes a general yellowing and dwarfing symptom. The phytoplasma is spread by a leafhopper vector.

Infected plants should be removed and destroyed. Early season control of the leafhopper vector and removal of weed hosts may help prevent re-infection.

Insect Problems:

See Perennials.