Key Features
- Stunted growth
- Yellowing of leaves
- Dark, poorly developed roots
Symptoms
Slow, stunted growth and yellowing leaves are generally the first detected symptoms of Thielaviopsis root rot. Additional symptoms may mimic those associated with nitrogen deficiency or drought. The pathogen, as well as the majority of the damage, remains below the soil. Exposing the roots will reveal a poorly developed system with stunted, black roots. Confirmation of any root rot requires laboratory diagnosis.
Biology
Thielaviopsis can survive in the soil for many years as thick-walled spores. Thielaviopsis infection prevents the roots from growing and lengthening. Poor quality roots cannot supply the leaves and stems with the water and nutrients required to grow. This leads to stunting, leaf yellowing, nutrient deficiencies, and drought-like symptoms.
Management Recommendations
Always purchase healthy looking plants from a reputable nursery. This disease is more of a problem for seedlings grown with hard water, which is often high in salt and alkaline in pH. Plants that appear stunted or stressed in the nursery may harbor pathogens in the potting media. Always check the roots of plants before purchasing and avoid plants with discolored or blackened roots. Likewise, avoid moving stunted, stressed, or diseased plants between landscapes or parts of the landscape. This will prevent the spreading the pathogen. A few thiophanate-methyl fungicides are labeled for Thielaviopsis control in home landscapes. Fungicide will not cure infected plants, however, the life of the plant may be extended and uninfected plants protected from the disease. Regular treatment may prevent new infections on neighboring plants.
Effective Pesticides
Active Ingredients include: Thiophanate-methyl
Resources
- Not satisfied with ID? Contact the Purdue Plant and Pest Diagnostic Lab
- Sign Up for the Purdue Landscape Report
