Several recent samples of petunia and calibrachoa have tested positive for black root rot (Thielaviopsis basicola) in Ohio. Symptoms inlcuded lack of rooting, stunting and slow growth with general failure to thrive, discolored foliage (often yellow or purple) – which can result in considerable crop losses. Black root rot also affects pansy, vinca and poinsettia. Ann Chase and GPN magazine recently published the following article on Black root rot with cultural and fungicide recommendations for control. GPN Black Root Rot article
Some key things to remember when dealing with Black root rot:
- Typical host plants include pansy, vinca, petunia, calibrachoa, poinsettia
- Difficult to eradicate once established
- Easily spread via propagation material and lack of sanitation
- Uneven growth is key indicator – along with stunted, blackened roots
- Prefers pH above 6.2, so maintain well-drained media with pH around 5.5
- Do not reuse flats or containers that held infected plants
Black root rot of calibrachoa
(Photo by Beth Scheckelhoff, The Ohio State University)
Black root rot in petunia
(Photo by Beth Scheckelhoff, The Ohio State University)
