Black Root Rot of Vinca

Disease Information

 Black Root Rot

 Symptoms and damage

Black root rot is caused by the fungus Thielaviopsisbasicola. The disease isn`t common on vinca in landscapes, but can be introduced by planting infected material or planting in areas where other, more susceptible hosts, such as pansies, have succumbed. As with all root rot diseases, infected plants are stunted and turn yellow. Washing and inspecting the root systems can point towards a black root rot diagnosis. Diseased plants have small root systems with a “salt-and-pepper” appearance. The root color results from the presence of dark fungal growth and black resting spores growing within the roots. As the disease becomes more severe, roots turn black and soft.

Management

Avoid planting vinca in areas where pansies have performed poorly or where Japanese hollies have died. Select plants with a healthy green appearance and uniform height. Fertilize according to soil test results, avoiding fertilizers with high ammonium content, such as ammonium nitrate or ammonium sulfate. High pH soils can lead to increased disease severity so apply lime only if needed. Remove and destroy all infected plants, including the entire root system. Thiophanate methyl (such as Cleary`s 3336-WP Turf & Ornamental Fungicide or Southern Ag Thiomyl Systemic Fungicide) can be applied to protect remaining plants.

 



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