Key Features
- Stunted, bushy growth
- Distorted leaves near crown
- Developed leaves unaffected
Symptoms
Rhodococcus proliferation is abnormal growth of leaf and stem tissue, typically from the crown of herbaceous perennials, though the symptoms can arise from any plant part infected by the bacteria Rhodococcus fasciens. A dense cluster of what resembles miniature plants or miniature leaves emerges from stunted branches. Similar symptoms can be caused by natural deformations in buds (fasciation), viral infections, or other pathogens. Samples can be sent to a plant disease diagnostic lab for confirmation.
Biology
Seeds and propagation material are often the main means of spread for Rhodococcus fasciens. The pathogen is often introduced to home landscapes through infected material purchased from a nursery. After the initial host dies, bacteria are splashed from the plant debris and soil to wounds on the base of herbaceous perennials. The bacteria cause new leaf and stem tissue to form near the site of colonization. This stunts the growth of the rest of the plant and creates dense clusters of dwarfed stems. This is often unsightly, but does not kill the plant. The disease may, to a small extent, be transmitted by insects.
Management Recommendations
Purchasing unaffected plants is the most important control measure for Rhodococcus proliferation. Cultural controls include protecting plants from injury. Care with lawn mowers and weed whips at the base of the herbaceous perennials will minimize infection. Practice good sanitation and remove infected plants.
Effective Pesticides
Pesticides are neither available nor recommended for managing this disease.
Resources
- Not satisfied with ID? Contact the Purdue Plant and Pest Diagnostic Lab
- Sign Up for the Purdue Landscape Report
